Linux Commands

System administration command. The Linux version of getty. Set terminal type, modes, speed, and line discipline. agetty is invoked by init. It is the second process in the series init-getty-login-shell, which ultimately connects a user with the Linux system. agetty reads the user's login name and invokes the login command with the user's name as an argument. While reading the name, agetty attempts to adapt the system to the speed and type of device being used.

You must specify a port, which agetty will search for in the /dev directory. You may use -, in which case agetty reads from standard input. You must also specify baudrate, which may be a comma-separated list of rates, through which agetty will step. Optionally, you may specify the term, which is used to override the TERM environment variable.

Options

• -h
• Specify hardware, not software, flow control.
• -i
• Suppress printing of /etc/issue before printing the login prompt.
• -l program
• Specify the use of program instead of /bin/login.
• -m
• Attempt to guess the appropriate baud rate.
• -t timeout
• Specify that agetty should exit if the open on the line succeeds and there is no response to the login prompt in timeout seconds.
• -L
• Do not require carrier detect; operate locally only. Use this when connecting terminals.

System administration command. apmd handles events reported by the Advanced Power Management BIOS driver. The driver reports on battery level and requests to enter sleep or suspend mode. apmd will log any reports it gets via syslogd and take steps to make sure that basic sleep and suspend requests are handled gracefully. You can fine-tune the behavior of apmd by specifying an apmd_proxy command to run when it receives an event.

Options

• -c n, --check n
• Set the number of seconds to wait for an event before rechecking the power level. Default is to wait indefinitely. Setting this causes the battery levels to be checked more frequently.
• -P command, --apmd_prxy command
• Specify the apmd_proxy command to run when APM driver events are reported. This is generally a shell script. The command will be invoked with parameters indicating what kind of event was received. The parameters are in the next list.
• -p n, --percentage n
• Log information whenever the power changes by n percent. The default is 5. Values greater than 100 will disable logging of power changes.
• -V, --version
• Print version and exit.
• -v, --version
• Verbose mode; all events are logged.
• -W, --wall
• Use wall to alert all users of a low battery status.
• -w n, --warn n
• Log a warning at ALERT level when the battery charge drops below n percent. The default is 10. Negative values disable low battery level warnings.
• -q, --quiet
• Disable low battery level warnings.
• -?, --help
• Print help summary and exit.

Parameters

The apmd proxy script will be invoked with the following parameters:

• start
• Invoked when the daemon starts.
• stop
• Invoked when the daemon stops.
• suspend [ system | user ]
• Invoked when a suspend request has been made. The second parameter indicates whether the request was made by the system or by the user.
• standby [ system | user ]
• Invoked when a standby request has been made. The second parameter indicates whether the request was made by the system or by the user.
• resume [ suspend | standby | critical ]
• Invoked when the system resumes normal operation. The second parameter indicates the mode the system was in before resuming. (critical suspends indicate an emergency shutdown. After a critical suspend the system may be unstable and you can use the resume command to help you recover from the suspension.
• change power
• Invoked when system power is changed from AC to battery or from battery to AC.
• change battery
• Invoked when the APM BIOS driver reports that the battery is low.
• change capability
• Invoked when the APM BIOS driver reports some hardware that affects its capability has been added or removed.

Search the short manual page descriptions in the whatis database for occurrences of each string and display the result on the standard output. Like whatis, except that it searches for strings instead of words. Equivalent to man -k.

Maintain a group of files that are combined into a file archive. Used most commonly to create and update library files as used by the link editor (ld). Only one key letter may be used, but each can be combined with additional args (with no separations between). posname is the name of a file in archive. When moving or replacing files, you can specify that they be placed before or after posname. -V prints the version number of ar on standard error.

Key

• d
• Delete files from archive.
• m
• Move files to end of archive.
• p
• Print files in archive.
• q
• Append files to archive.
• r
• Replace files in archive.
• t
• List the contents of archive or list the named files.
• x
• Extract contents from archive or only the named files.

Arguments

• a
• Use with r or m key to place files in the archive after posname.
• b
• Same as a but before posname.
• c
• Create archive silently.
• f
• Truncate long filenames.
• i
• Same as b.
• l
• For backward compatibility; meaningless in Linux.
• o
• Preserve original timestamps.
• s
• Force regeneration of archive symbol table (useful after running strip).
• S
• Do not regenerate symbol table.
• u
• Use with r to replace only files that have changed since being put in archive.
• v
• Verbose; print a description of actions taken.

Example

Replace mylib.a with object files from the current directory:

ar r mylib.a `ls *.o

Print machine architecture type to standard output. Equivalent to uname -m.

TCP/IP command. Clear, add to, or dump the kernel's ARP cache (/proc/net/arp).

Options

• -v
• Verbose mode.
• -t type
• Search for type entries when examining the ARP cache. type must be ether (Ethernet) or ax25 (AX.25 packet radio); ether is the default.
• -a [hosts]
• Display hosts' entries or, if none are specified, all entries.
• -d host
• Remove host's entry.
• -s host hardware-address
• Add the entry host hardware-address, where ether class addresses are 6 hexadecimal bytes, colon-separated.
• -f file
• Read entries from file and add them.

Generate an object file from each specified assembly language source file. Object files have the same root name as source files but replace the s suffix with o. There may be some additional system-specific options.

Options

• -- [ | files]
• Read input files from standard input, or from files if the pipe is used.
• -a[dhlns][=file]
• With only the -a option, list source code, assembler listing, and symbol table. The other options specify additional things to list or omit:
  • -ad
  • Omit debugging directives.
  • -ah
  • Include the high-level source code, if available.
  • -al
  • Include an assembly listing.
  • -an
  • Suppress forms processing.
  • -as
  • Include a symbol listing.
  • =file
  • Set the listing filename to file.
• -defsym symbol=value
• Define the symbol to have the value value, which must be an integer.
• -f
• Skip preprocessing.
• --gstabs
• Generate stabs debugging information.
• -o objfile
• Place output in object file objfile (default is fileo).
• -v
• Display the version number of the assembler.
• -I path
• Include path when searching for include directives.
• -K
• Warn before altering difference tables.
• -L
• Do not remove local symbols, which begin with L.
• -R
• Combine both data and text in text section.
• -W
• Quiet mode.

Execute commands at a specified time and optional date. The commands are read from standard input or from a file. (See also batch.) End input with EOF. time can be formed either as a numeric hour (with optional minutes and modifiers) or as a keyword. It can contain an optional date, formed as a month and date, a day of the week, or a special keyword (today or tomorrow). An increment can also be specified.

The at command can always be issued by a privileged user. Other users must be listed in the file /etc/at.allow if it exists; otherwise, they must not be listed in /etc/at.deny. If neither file exists, only a privileged user can issue the command.

Options

• -c job [job...]
• Display the specified jobs on the standard output. This option does not take a time specification.
• -d job [job...]
• Delete the specified jobs. Same as atrm.
• -f file
• Read job from file, not standard input.
• -l
• Report all jobs that are scheduled for the invoking user. Same as atq.
• -m
• Mail user when job has completed, regardless of whether output was created.
• -q letter
• Place job in queue denoted by letter, where letter is any single letter from a-z or A-Z. Default queue is a. (The batch queue defaults to b.) Higher-lettered queues run at a lower priority.
• -V
• Display the version number.

Time

• hh:mm [modifiers]
• Hours can have one digit or two (a 24-hour clock is assumed by default); optional minutes can be given as one or two digits; the colon can be omitted if the format is h, hh, or hhmm; (e.g., valid times are 5, 5:30, 0530, 19:45). If modifier am or pm is added, time is based on a 12-hour clock. If the keyword zulu is added, times correspond to Greenwich Mean Time.
• midnight | noon | teatime | now
• Use any one of these keywords in place of a numeric time. teatime translates to 4:00 p.m.; now must be followed by an increment.

Date

• month num[ year]
• month is one of the 12 months, spelled out or abbreviated to its first three letters; num is the calendar date of the month; year is the four-digit year. If the given month occurs before the current month, at schedules that month next year.
• day
• One of the seven days of the week, spelled out or abbreviated to its first three letters.
• today | tomorrow
• Indicate the current day or the next day. If date is omitted, at schedules today when the specified time occurs later than the current time; otherwise, at schedules tomorrow.

Increment

Supply a numeric increment if you want to specify an execution time or day relative to the current time. The number should precede any of the keywords minute, hour, day, week, month, or year (or their plural forms). The keyword next can be used as a synonym of + 1.

Examples

Note that the first two commands are equivalent:

at 1945 pm December 9 at 7:45pm Dec 9 at 3 am Saturday at now + 5 hours at noon next day

List the user's pending jobs, unless the user is a privileged user; in that case, everybody's jobs are listed. Same as at -l.

Options

• -q queue
• Query only the specified queue and ignore all other queues.
• -v
• Show jobs that have completed but not yet been deleted.
• -V
• Print the version number.

Delete jobs that have been queued for future execution. Same as at -d.

Options

• -q queue
• Remove job from the specified queue.
• -V
• Print the version number and then exit.

System administration command. Search device for bad blocks. You must specify the number of blocks on the device (block-count).

Options

• -b blocksize
• Expect blocksize-byte blocks.
• -o file
• Direct output to file.
• -v
• Verbose mode.
• -w
• Test by writing to each block and then reading back from it.

Print characters as a poster. If no characters are supplied, banner prompts for them and reads an input line from standard input. By default, the results go to standard output, but they are intended to be sent to a printer.

Option

• -w width
• Set width to width characters. Note that if your banner is in all lowercase, it will be narrower than width characters. If -w is not specified, the default width is 132. If -w is specified but width is not provided, the default is 80.

Example

/usr/games/banner -w50 Happy Birthday! |lpr

basename option

Remove leading directory components from a path. If suffix is given, remove that also. The result is printed to standard output.

Options

• --help
• Print help message and then exit.
• --version
• Print the version number and then exit.

Examples

% basename /usr/lib/libm.a libm.a % basename /usr/lib/libm.a .a libm

Execute commands entered on standard input. If time is omitted, execute them when the system load permits (when the load average falls below 0.8). Very similar to at, but does not insist that the execution time be entered on the command line. See at for details.

Options

• -f file
• Read job from file, not standard input.
• -m
• Mail user when job has completed, regardless of whether output was created.
• -q letter
• Place job in queue denoted by letter, where letter is one letter from a-z or A-Z. The default queue is a. (The batch queue defaults to b.) Higher-lettered queues run at a lower priority.
• -V
• Print the version number and then exit.
• -v
• Display the time a job will be executed.

sh [options] [file [arguments]]

Standard Linux shell, a command interpreter into which all other commands are entered. For more information, see "bash: The Bourne-Again Shell".

bc is a language (and compiler) whose syntax resembles that of C, but with unlimited-precision arithmetic. bc consists of identifiers, keywords, and symbols, which are briefly described in the following entries. Examples are given at the end.

Interactively perform arbitrary-precision arithmetic or convert numbers from one base to another. Input can be taken from files or read from the standard input. To exit, type quit or EOF.

Options

• -l, --mathlib
• Make functions from the math library available.
• -s, --standard
• Ignore all extensions, and process exactly as in POSIX.
• -w, --warn
• When extensions to POSIX bc are used, print a warning.
• -q, --quiet
• Do not display welcome message.
• -v, --version
• Print version number.

Identifiers

An identifier is a series of one or more characters. It must begin with a lowercase letter but may also contain digits and underscores. No uppercase letters are allowed. Identifiers are used as names for variables, arrays, and functions. Variables normally store arbitrary-precision numbers. Within the same program you may name a variable, an array, and a function using the same letter. The following identifiers would not conflict:

• x
• Variable x.
• x[i]
• Element i of array x. i can range from 0 to 2047 and can also be an expression.
• x(y,z)
• Call function x with parameters y and z.

Input-output keywords

ibase, obase, scale, and last store a value. Typing them on a line by themselves displays their current value. You can also change their values through assignment. The letters A-F are treated as digits whose values are 10-15.

• ibase = n
• Numbers that are input (e.g., typed) are read as base n (default is 10).
• obase = n
• Numbers that are displayed are in base n (default is 10). Note: Once ibase has been changed from 10, use A to restore ibase or obase to decimal.
• scale = n
• Display computations using n decimal places (default is 0, meaning that results are truncated to integers). scale is normally used only for base-10 computations.
• last
• Value of last printed number.

Statement keywords

A semicolon or a newline separates one statement from another. Curly braces are needed when grouping multiple statements.

• if (rel-expr) {statements} [else {statements}]
• Do one or more statements if relational expression rel-expr is true. Otherwise, do nothing, or if else (an extension) is specified, do alternative statements. For example:

 if(x==y) {i = i + 1} else {i = i - 1}

• while (rel-expr) {statements}
• Repeat one or more statements while rel-expr is true; for example:

 while(i>0) {p = p*n; q = a/b; i = i-1}

• for (expr1;rel-expr;expr2) {statements}
• Similar to while; for example, to print the first 10 multiples of 5, you could type:

 for(i=1; i<=10; i++) i*5

GNU bf does not require three arguments to for. A missing argument 1 or 3 means that those expressions will never be evaluated. A missing argument 2 evaluates to the value 1.

• break
• Terminate a while or for statement.
• print list
• GNU extension. It provides an alternate means of output. list consists of a series of comma-separated strings and expressions; print displays these entities in the order of the list. It does not print a newline when it terminates. Expressions are evaluated, printed, and assigned to the special variable last. Strings (which may contain special characters, i.e., characters beginning with ) are simply printed. Special characters can be:
  • a
  • Alert or bell
  • b
  • Backspace
  • f
  • Form feed
  • n
  • Newline
  • r
  • Carriage return
  • q
  • Double quote
  • t
  • Tab
  • Backslash
• continue
• GNU extension. When within a for statement, jump to the next iteration.
• halt
• GNU extension. Cause the bc processor to quit.
• limits
• GNU extension. Print the limits enforced by the local version of bc.

Function keywords

• define f(args) {
• Begin the definition of function f having the arguments args. The arguments are separated by commas. Statements follow on successive lines. End with a }.
• auto x, y
• Set up x and y as variables local to a function definition, initialized to 0 and meaningless outside the function. Must appear first.
• return(expr)
• Pass the value of expression expr back to the program. Return 0 if (expr) is left off. Used in function definitions.
• sqrt(expr)
• Compute the square root of expression expr.
• length(expr)
• Compute how many significant digits are in expr.
• scale(expr)
• Same as length, but count only digits to the right of the decimal point.
• read( )
• GNU extension. Read a number from standard input. Return value is the number read, converted via the value of ibase.

Math library functions

These are available when bc is invoked with -l. Library functions set scale to 20.

• s(angle)
• Compute the sine of angle, a constant or expression in radians.
• c(angle)
• Compute the cosine of angle, a constant or expression in radians.
• a(n)
• Compute the arctangent of n, returning an angle in radians.
• e(expr)
• Compute e to the power of expr.
• l(expr)
• Compute the natural log of expr.
• j(n x)
• Compute the Bessel function of integer order n.

Operators

These consist of operators and other symbols. Operators can be arithmetic, unary, assignment, or relational:

• arithmetic
• + - * / % ^
• unary
• - ++ --
• assignment
• =+ =- =* =/ =% =^ =
• relational
• < <= > >= == !=

Other symbols

• /* */
• Enclose comments.
• ()
• Control the evaluation of expressions (change precedence). Can also be used around assignment statements to force the result to print.
• {}
• Use to group statements.
• []
• Indicate array index.
• "text"
• Use as a statement to print text.

Examples

Note in these examples that when you type some quantity (a number or expression), it is evaluated and printed, but assignment statements produce no display.

ibase = 8 Octal input 20 Evaluate this octal number 16 Terminal displays decimal value obase = 2 Display output in base 2 instead of base 10 20 Octal input 10000 Terminal now displays binary value ibase = A Restore base-10 input scale = 3 Truncate results to 3 decimal places 8/7 Evaluate a division 1.001001000 Oops! Forgot to reset output base to 10 obase=10 Input is decimal now, so A isn't needed 8/7 1.142 Terminal displays result (truncated)

The following lines show the use of functions:

define p(r,n){ Function p uses two arguments auto v v is a local variable v = r^n r raised to the n power return(v)} Value returned scale=5 x=p(2.5,2) x = 2.5 ^ 2 x Print value of x 6.25 length(x) Number of digits 3 scale(x) Number of places right of decimal point 2

Notify user of mail arrival and sender's name. biff operates asynchronously. Mail notification works only if your system is running the comsat(8) server. The command biff y enables notification, and the command biff n disables notification. With no arguments, biff reports biff's current status.

Given a file containing context-free grammar, convert into tables for subsequent parsing while sending output to file.c. This utility is both to a large extent compatible with yacc and named for it. All input files should use the suffix y; output files will use the original prefix. All long options (those preceded by --) may instead be preceded by +.

Options

• -b prefix, --file-prefix=prefix
• Use prefix for all output files.
• -d, --defines
• Generate file.h, producing #define statements that relate bison's token codes to the token names declared by the user.
• -r, --raw
• Use bison token numbers, not yacc-compatible translations, in file.h.
• -k, --token-table
• Include token names and values of YYNTOKENS, YYNNTS, YYNRULES, and YYNSTATES in file.c.
• -l, --no-lines
• Exclude #line constructs from code produced in file.c. (Use after debugging is complete.)
• -n, --no-parser
• Suppress parser code in output, allowing only declarations. Assemble all translations into a switch statement body and print it to file.act.
• -o file, --output-file=file
• Output to file.
• -p prefix, --name-prefix=prefix
• Substitute prefix for yy in all external symbols.
• -t, --debug
• Compile runtime debugging code.
• -v, --verbose
• Verbose mode. Print diagnostics and notes about parsing tables to file.output.
• -V, --version
• Display version number.
• -y, --yacc, --fixed-output-files
• Duplicate yacc's conventions for naming output files.

TCP/IP command. Internet Boot Protocol server. bootpd normally is run by /etc/inetd by including the following line in the file /etc/inetd.conf:

bootps dgram udp wait root /etc/bootpd bootpd

This causes bootpd to be started only when a boot request arrives. It may also be started in standalone mode, from the command line. Upon startup, bootpd first reads its configuration file, /etc/bootptab (or the configfile listed on the command line), then begins listening for BOOTREQUEST packets.

bootpd looks in /etc/services to find the port numbers it should use. Two entries are extracted: bootps -- the bootp server listening port -- and bootpc -- the destination port used to reply to clients.

If bootpd is compiled with the -DDEBUG option, receipt of a SIGUSR1 signal causes it to dump its memory-resident database to the file /etc/bootpd.dump or the command-line specified dumpfile.

Options

• -c directory
• Force bootpd to work in directory.
• -d level
• Specify the debugging level. Omitting level will increment the level by 1.
• -t timeout
• Specify a timeout value in minutes. A timeout value of 0 means wait forever.

Configuration file

The bootpd configuration file has a format in which two-character, case-sensitive tag symbols are used to represent host parameters. These parameter declarations are separated by colons. The general format is:

hostname:tg=value:tg=value:tg=value

where hostname is the name of a bootp client and tg is a tag symbol. The currently recognized tags are listed next.

Tags

There is also a generic tag, Tn, where n is an RFC 1048 vendor field tag number. Generic data may be represented as either a stream of hexadecimal numbers or as a quoted string of ASCII characters.

Internet Boot Protocol Gateway. Maintain a gateway that forwards bootpd requests to server. In addition to dealing with BOOTREPLY packets, also deal with BOOTREQUEST packets. bootpgw is normally run by /etc/inetd by including the following line in the file /etc/inetd.conf:

bootps dgram udp wait root /etc/bootpgw bootpgw

This causes bootpgw to be started only when a boot request arrives. bootpgw takes all the same options as bootpd, except -c.

TCP/IP command. Test server's bootpd daemon by sending requests every second for 10 seconds or until the server responds. Read options from the template file, if provided.

Options

• -f file
• Read the boot filename from file.
• -h
• Identify client by hardware, not IP, address.
• -m magic-number
• Provide magic-number as the first word of the vendor options field.

bunzip2 [options] filenames

bzcat [option] filenames

bzip2recover filenames

File compression and decompression utility similar to gzip, but uses a different algorithm and encoding method to get better compression. bzip2 replaces each file in filenames with a compressed version of the file and with a bz2 extension appended. bunzip2 decompresses each file compressed by bzip2 (ignoring other files, except to print a warning). bzcat decompresses all specified files to standard output, and bzip2recover is used to try to recover data from damaged files.

Options

• --
• End of options; treat all subsequent arguments as filenames.
• -dig
• Set block size to dig × 100KB when compressing, where dig is a single digit from 1 to 9.
• -c, --stdout
• Compress or decompress to standard output.
• -d, --decompress
• Force decompression.
• -f, --force
• Force overwrite of output files. Default is not to overwrite. Also forces breaking of hard links to files.
• -k, --keep
• Keep input files; don't delete them.
• -L, --license, -V, --version
• Print license and version information and exit.
• -q, --quiet
• Quiet. Print only critical messages.
• -s, --small
• Use less memory, at the expense of speed.
• -t, --test
• Check the integrity of the files, but don't actually compress them.
• -v, --verbose
• Verbose. Show the compression ratio for each file processed. Add more -v's to increase the verbosity.
• -z, --compress
• Forces compression, even if invoked as bunzip2 or bzcat.
• --repetitive-fast, --repetitive-best
• Sometimes useful in versions earlier than 0.9.5 (which has an improved sorting algorithm) for providing some control over the algorithm.

See g++.

Print a 12-month calendar (beginning with January) for the given year or a one-month calendar of the given month and year. month ranges from 1 to 12. year ranges from 1 to 9999. With no arguments, print a calendar for the current month.

Options

• -j
• Display Julian dates (days numbered 1 to 365, starting from January 1).
• -m
• Display Monday as the first day of the week.
• -y
• Display entire year.

Examples

cal 12 1995 cal 1994 > year_file

System administration command. Control PCMCIA sockets or select the current scheme. The current scheme is sent along with the address of any inserted cards to configuration scripts (by default located in /etc/pcmcia). The scheme command displays or changes the scheme. The other commands operate on a named card socket number or, if no number is given, all sockets.

Commands

• config [socket]
• Display current socket configuration.
• eject [socket]
• Prepare the system for the card(s) to be ejected.
• ident [socket]
• Display card identification information.
• insert [socket]
• Notify system that a card has been inserted.
• reset [socket]
• Send reset signal to card.
• resume [socket]
• Restore power to socket and reconfigure for use.
• scheme [name]
• Display current scheme or change to specified scheme name.
• status [socket]
• Display current socket status.
• suspend [socket]
• Shut down device and cut power to socket.

Options

• -c directory
• Look for card configuration information in directory instead of /etc/pcmcia.
• -f file
• Use file to keep track of the current scheme instead of /var/run/pcmcia-scheme.
• -s file
• Look for current socket information in file instead of /var/run/stab.

System administration command. The PCMCIA card daemon. cardmgr monitors PCMCIA sockets for devices that have been added or removed. When a card is detected, it attempts to get the card's ID and configure it according to the card configuration database (usually stored in /etc/pcmcia/config). By default, cardmgr both creates a system log entry when it detects cards and beeps. Two high beeps mean it successfully identified and configured a device. One high beep followed by one low beep means it identified the device, but was unable to configure it successfully. One low beep means it could not identify the inserted card. Information on the currently configured cards can be found in /var/run/stab.

Options

• -cdirectory
• Look in directory for the card configuration database instead of /etc/pcmcia.
• -d
• use modprobe instead of insmod to load the PCMCIA device driver.
• -f
• Run in the foreground to process the current cards, then run as a daemon.
• -mdirectory
• Look in directory for card device modules instead of /lib/modules/ `uname -r`.
• -o
• Configure the cards present in one pass, then exit.
• -pfile
• Write cardmgr's process ID to file instead of /var/run/cardmgr.pid.
• -q
• Run in quiet mode. No beeps.
• -sfile
• Write current socket information to file instead of /var/run/stab.
• -v
• Verbose mode.
• -V
• Print version number and exit.

Read (concatenates) one or more files and print them on standard output. Read standard input if no files are specified or if - is specified as one of the files; input ends with EOF. You can use the > operator to combine several files into a new file or >> to append files to an existing file.

Options

• -A, --show-all
• Same as -vET.
• -b, --number-nonblank
• Number all nonblank output lines, starting with 1.
• -e
• Same as -vE.
• -E, --show-ends
• Print $ at the end of each line.
• -n, --number
• Number all output lines, starting with 1.
• -s, --squeeze-blank
• Squeeze down multiple blank lines to one blank line.
• -t
• Same as -vT.
• -T, --show-tabs
• Print TAB characters as ^I.
• -u
• Ignored; retained for Unix compatibility.
• -v, --show-nonprinting
• Display control and nonprinting characters, with the exception of LINEFEED and TAB.

Examples

cat ch1 Display a file cat ch1 ch2 ch3 > all Combine files cat note5 >> notes Append to a file cat > temp1 Create file at terminal; end with EOF cat > temp2 << STOP Create file at terminal; end with STOP

See gcc.

GNU C language preprocessor. cpp is invoked as the first pass of any C compilation by the gcc command. The output of cpp is a form acceptable as input to the next pass of the C compiler, and cpp normally invokes gcc after it finishes processing. ifile and ofile are, respectively, the input and output for the preprocessor; they default to standard input and standard output.

Options

• -$
• Do not allow $ in identifiers.
• -dM
• Suppress normal output. Print series of #defines that create the macros used in the source file.
• -dD
• Similar to -dM but exclude predefined macros and include results of preprocessing.
• -idirafter dir
• Search dir for header files when a header file is not found in any of the included directories.
• -imacros file
• Process macros in file before processing main files.
• -include file
• Process file before main file.
• -iprefix prefix
• When adding directories with -iwithprefix, prepend prefix to the directory's name.
• -iwithprefix dir
• Append dir to the list of directories to be searched when a header file cannot be found in the main include path. If -iprefix has been set, prepend that prefix to the directory's name.
• -lang-c, -lang-c++, -lang-objc, -lang-objc++
• Expect the source to be in C, C++, Objective C, or Objective C++, respectively.
• -lint
• Display all lint commands in comments as #pragma lint command.
• -nostdinc
• Search only specified, not standard, directories for header files.
• -nostdinc++
• Suppress searching of directories believed to contain C++-specific header files.
• -pedantic
• Warn verbosely.
• -pedantic-errors
• Produce a fatal error in every case in which -pedantic would have produced a warning.
• -traditional
• Behave like traditional C, not ANSI.
• -undef
• Suppress definition of all nonstandard macros.
• -Aname[=def]
• Assert name with value def as if defined by a #assert.
• -C
• Pass along all comments (except those found on cpp directive lines). By default, cpp strips C-style comments.
• -Dname[=def]
• Define name with value def as if by a #define. If no =def is given, name is defined with value 1. -D has lower precedence than -U.
• -H
• Print pathnames of included files, one per line, on standard error.
• -Idir
• Search in directory dir for #include files whose names do not begin with / before looking in directories on standard list. #include files whose names are enclosed in double quotes and do not begin with / will be searched for first in the current directory, then in directories named on -I options, and last in directories on the standard list.
• -M [-MG]
• Suppress normal output. Print a rule for make that describes the main source file's dependencies. If -MG is specified, assume that missing header files are actually generated files, and look for them in the source file's directory.
• -MD file
• Similar to -M, but output to file; also compile the source.
• -MM
• Similar to -M. Describe only those files included as a result of #include "file".
• -MMD file
• Similar to -MD, but describe only the user's header files.
• -P
• Preprocess input without producing line-control information used by next pass of C compiler.
• -Uname
• Remove any initial definition of name, where name is a reserved symbol predefined by the preprocessor or a name defined on a -D option. Names predefined by cpp are unix and i386 (for Intel systems).
• -Wcomment, -Wcomments
• Warn when encountering the beginning of a nested comment.
• -Wtraditional
• Warn when encountering constructs that are interpreted differently in ANSI from traditional C.

Special names

cpp understands various special names, some of which are:

• __DATE__
• Current date (e.g., Oct 10 1999)
• __FILE__
• Current filename (as a C string)
• __LINE__
• Current source line number (as a decimal integer)
• __TIME__
• Current time (e.g., 12:00:00)

These special names can be used anywhere, including macros, just like any other defined names. cpp's understanding of the line number and filename may be changed using a #line directive.

Directives

All cpp directive lines start with # in column 1. Any number of blanks and tabs is allowed between the # and the directive. The directives are:

• #assert name (string)
• Define a question called name, with an answer of string. Assertions can be tested with #if directives. The predefined assertions for #system, #cpu, and #machine can be used for architecture-dependent changes.
• #unassert name
• Remove assertion for question name.
• #define name token-string
• Define a macro called name, with a value of token-string. Subsequent instances of name are replaced with token-string.
• #define name( arg, ... , arg ) token-string
• This allows substitution of a macro with arguments. token-string will be substituted for name in the input file. Each call to name in the source file includes arguments that are plugged into the corresponding args in token-string.
• #undef name
• Remove definition of the macro name. No additional tokens are permitted on the directive line after name.
• #ident string
• Put string into the comment section of an object file.
• #include "filename", #include<filename>
• Include contents of filename at this point in the program. No additional tokens are permitted on the directive line after the final " or >.
• #lineinteger-constant "filename"
• Cause cpp to generate line-control information for the next pass of the C compiler. The compiler behaves as if integer-constant is the line number of the next line of source code and filename (if present) is the name of the input file. No additional tokens are permitted on the directive line after the optional filename.
• #endif
• End a section of lines begun by a test directive (#if, #ifdef, or #ifndef). No additional tokens are permitted on the directive line.
• #ifdef name
• Lines following this directive and up to matching #endif or next #else or #elif will appear in the output if name is currently defined. No additional tokens are permitted on the directive line after name.
• #ifndef name
• Lines following this directive and up to matching #endif or next #else or #elif will appear in the output if name is not currently defined. No additional tokens are permitted on the directive line after name.
• #if constant-expression
• Lines following this directive and up to matching #endif or next #else or #elif will appear in the output if constant-expression evaluates to nonzero.
• #elif constant-expression
• An arbitrary number of #elif directives are allowed between an #if, #ifdef, or #ifndef directive and an #else or #endif directive. The lines following the #elif and up to the next #else, #elif, or #endif directive will appear in the output if the preceding test directive and all intervening #elif directives evaluate to zero, and the constant-expression evaluates to nonzero. If constant-expression evaluates to nonzero, all succeeding #elif and #else directives will be ignored.
• #else
• Lines following this directive and up to the matching #endif will appear in the output if the preceding test directive evaluates to 0, and all intervening #elif directives evaluate to 0. No additional tokens are permitted on the directive line.
• #error
• Report fatal errors.
• #warning
• Report warnings, but then continue processing.

System administration command. Partition a hard disk. device may be /dev/hda (default), /dev/hdb, /dev/sda, /dev/sdb, /dev/sdc, or /dev/sdd. See also fdisk.

Options

• -a
• Highlight the current partition with a cursor, not reverse video.
• -c cylinders
• Specify the number of cylinders.
• -h heads
• Specify the number of heads.
• -s sectors
• Specify the number of sectors per track.
• -z
• Do not read the partition table; partition from scratch.
• -P format
• Display the partition table in format, which must be r (raw data), s (sector order), or t (raw format).

Commands

• up arrow, down arrow
• Move among partitions.
• b
• Toggle partition's bootable flag.
• d
• Delete partition (allow other partitions to use its space).
• g
• Alter the disk's geometry. Prompt for what to change: cylinders, heads, or sectors (c, h, or s, respectively).
• h
• Help.
• m
• Attempt to ensure maximum usage of disk space in the partition.
• n
• Create a new partition. Prompt for more information.
• p
• Display the partition table.
• q
• Quit without saving information.
• t
• Prompt for a new filesystem type, and change to that type.
• u
• Change the partition size units, rotating from megabytes to sectors to cylinders and back.
• W
• Save information. Note that this letter must be uppercase.

Modify file attributes. Specific to Linux Second Extended Filesystem. Behaves similarly to symbolic chmod, using +, -, and =. mode is in the form opcode attribute. See also lsattr.

Options

• -R
• Modify directories and their contents recursively.
• -V
• Print modes of attributes after changing them.
• -v version
• Set the file's version.

Opcodes

• +
• Add attribute.
• -
• Remove attribute.
• =
• Assign attributes (removing unspecified attributes).

Attributes

• A
• Don't update access time on modify.
• a
• Append only for writing. Can be set or cleared only by a privileged user.
• c
• Compressed.
• d
• No dump.
• i
• Immutable. Can be set or cleared only by a privileged user.
• s
• Secure deletion; the contents are zeroed on deletion.
• u
• Undeletable.
• S
• Synchronous updates.

Examples

chattr +a myfile As superuser

Change the information that is stored in /etc/passwd and displayed when a user is fingered. Without options, chfn enters interactive mode and prompts for changes. To make a field blank, enter the keyword none. Only a privileged user can change information for another user. For regular users, chfn prompts for the user's password before making the change.

Options

• -f, --full-name
• Specify new full name.
• -h, --home-phone
• Specify new home phone number.
• -o, --office
• Specify new office number.
• -p, --office-phone
• Specify new office phone number.
• -u, --help
• Print help message and then exit.
• -v, --version
• Print version information and then exit.

Example

chfn -f "Ellen Siever" ellen

chgrp [options]

Change the group of one or more files to newgroup. newgroup is either a group ID number or a group name located in /etc/group. Only the owner of a file or a privileged user may change its group.

Options

• -c, --changes
• Print information about those files that are changed.
• -f, --silent, --quiet
• Do not print error messages about files that cannot be changed.
• --help
• Print help message and then exit.
• -R, --recursive
• Traverse subdirectories recursively, applying changes.
• --reference=filename
• Change the group to that associated with filename. In this case, newgroup is not specified.
• -v, --verbose
• Verbosely describe ownership changes.
• --version
• Print version information and then exit.

chmod [options] --reference=filename files

Change the access mode (permissions) of one or more files. Only the owner of a file or a privileged user may change its mode. mode can be numeric or an expression in the form of who opcode permission. who is optional (if omitted, default is a); choose only one opcode. Multiple modes may be specified, separated by commas.

Options

• -c, --changes
• Print information about files that are changed.
• -f, --silent, --quiet
• Do not notify user of files that chmod cannot change.
• --help
• Print help message and then exit.
• -R, --recursive
• Traverse subdirectories recursively, applying changes.
• --reference=filename
• Change permissions to those associated with filename.
• -v, --verbose
• Print information about each file, whether changed or not.
• --version
• Print version information and then exit.

Who

• u
• User
• g
• Group
• o
• Other
• a
• All (default)

Opcode

• +
• Add permission.
• -
• Remove permission.
• =
• Assign permission (and remove permission of the unspecified fields).

Permissions

• r
• Read.
• w
• Write.
• x
• Execute.
• s
• Set user (or group) ID.
• t
• Sticky bit; save text (file) mode or prevent removal of files by nonowners (directory).
• u
• User's present permission.
• g
• Group's present permission.
• o
• Other's present permission.

Alternatively, specify permissions by a three-digit octal number. The first digit designates owner permission; the second, group permission; and the third, other's permission. Permissions are calculated by adding the following octal values:

• Read.
• Write.
• Execute.

Note: A fourth digit may precede this sequence. This digit assigns the following modes:

• Set user ID on execution to grant permissions to process based on file's owner, not on permissions of user who created the process.
• Set group ID on execution to grant permissions to process based on the file's group, not on permissions of user who created the process.
• Set sticky bit.

Examples

Add execute-by-user permission to file:

chmod u+x file

Either of the following will assign read/write/execute permission by owner (7), read/execute permission by group (5), and execute-only permission by others (1) to file:

chmod 751 file chmod u=rwx,g=rx,o=x file

Any one of the following will assign read-only permission to file for everyone:

chmod =r file chmod 444 file chmod a-wx,a+r file

Set the user ID, assign read/write/execute permission by owner, and assign read/execute permission by group and others:

chmod 4755 file

chown [options] --reference=filename files

Change the ownership of one or more files to newowner. newowner is either a user ID number or a login name located in /etc/passwd. chown also accepts users in the form newowner:newgroup or newowner.newgroup. The last two forms change the group ownership as well. If no owner is specified, the owner is unchanged. With a period or colon but no group, the group is changed to that of the new owner. Only the current owner of a file or a privileged user may change its owner.

Options

• -c, --changes
• Print information about those files that are changed.
• --dereference
• Follow symbolic links.
• -f, --silent, --quiet
• Do not print error messages about files that cannot be changed.
• -h, --no-dereference
• Change the ownership of each symbolic link (on systems that allow it), rather than the referenced file.
• -v, --verbose
• Print information about all files that chown attempts to change, whether or not they are actually changed.
• -R, --recursive
• Traverse subdirectories recursively, applying changes.
• --reference=filename
• Change owner to the owner of filename instead of specifying a new owner explicitly.
• --help
• Print help message and then exit.
• --version
• Print version information and then exit.

System administration command. Change user passwords in a batch. chpasswd accepts input in the form of one username:password pair per line. If the -e option is not specified, password will be encrypted before being stored.

Option

• -e
• Passwords given are already encrypted.

System administration command. Change root directory for command or, if none is specified, for a new copy of the user's shell. This command or shell is executed relative to the new root. The meaning of any initial / in pathnames is changed to newroot for a command and any of its children. In addition, the initial working directory is newroot. This command is restricted to privileged users.

Change your login shell, interactively or on the command line. Warn if shell does not exist in /etc/shells. Specify the full path to the shell. chsh prompts for your password. Only a privileged user can change another user's shell.

Options

• -l, --list-shells
• Print valid shells, as listed in /etc/shells, and then exit.
• -sshell, --shellshell
• Specify new login shell.
• -u, --help
• Print help message and then exit.
• -v, --version
• Print version information and then exit.

Example

chsh -s /bin/tcsh

Compute a cyclic redundancy check (CRC) checksum for all files; used to ensure that a file was not corrupted during transfer. Read from standard input if the character - or no files are given. Display the resulting checksum, the number of bytes in the file, and (unless reading from standard input) the filename.

Clear the terminal display.

Compare file1 with file2. Use standard input if file1 is - or missing. See also comm and diff. Files can be of any type. skip1 and skip2 are optional offsets in the files at which the comparison is to start.

Options

• -c, --print-chars
• Print differing bytes as characters.
• -i num, --ignore-initial=num
• Ignore the first num bytes of input.
• -l, --verbose
• Print offsets and codes of all differing bytes.
• -s, --quiet, --silent
• Work silently; print nothing, but return exit codes:
  • Files are identical.
  • Files are different.
  • Files are inaccessible.

Example

Print a message if two files are the same (exit code is 0):

cmp -s old new && echo 'no changes'

A postprocessing filter that handles reverse linefeeds and escape characters, allowing output from tbl or nroff to appear in reasonable form on a terminal.

Options

• -b
• Ignore backspace characters; helpful when printing manpages.
• -f
• Process half-line vertical motions, but not reverse line motion. (Normally, half-line input motion is displayed on the next full line.)
• -l n
• Buffer at least n lines in memory. The default buffer size is 128 lines.
• -x
• Normally, col saves printing time by converting sequences of spaces to tabs. Use -x to suppress this conversion.

Examples

Run myfile through tbl and nroff, then capture output on screen by filtering through col and more:

tbl myfile | nroff | col | more

Save manpage output for the ls command in out.print, stripping out backspaces (which would otherwise appear as ^H):

man ls | col -b > out.print

A postprocessing filter that handles reverse linefeeds and escape characters, allowing output from tbl or nroff to appear in reasonable form on a terminal. Put half-line characters (e.g., subscripts or superscripts) and underlining (changed to dashes) on a new line between output lines.

Options

• -
• Do not underline.
• -2
• Double space by printing all half-lines.

Remove specified columns from a file, where a column is a single character in a line. Read from standard input and write to standard output. Columns are numbered starting with 1; begin deleting columns at (including) the start column, and stop at (including) the stop column. Entering a tab increments the column count to the next multiple of either the start or stop column; entering a backspace decrements it by 1.

Example

colrm 3 5 < test1 > test2

Format input from one or more files into columns, filling rows first. Read from standard input if no files are specified.

Options

• -c num
• Format output into num columns.
• -s char
• Delimit table columns with char. Meaningful only with -t.
• -t
• Format input into a table. Delimit with whitespace, unless an alternate delimiter has been provided with -s.
• -x
• Fill columns before filling rows.

Compare lines common to the sorted files file1 and file2. Three-column output is produced: lines unique to file1, lines unique to file2, and lines common to both files. comm is similar to diff in that both commands compare two files. But comm can also be used like uniq; that is, comm selects duplicate or unique lines between two sorted files, whereas uniq selects duplicate or unique lines within the same sorted file.

Options

• -
• Read the standard input.
• -num
• Suppress printing of column num. Multiple columns may be specified and should not be space-separated.
• --help
• Print help message and exit.
• --version
• Print version information and exit.

Example

Compare two lists of top-10 movies, and display items that appear in both lists:

comm -12 siskel_top10 ebert_top10

Compress one or more files, replacing each with the compressed file of the same name with Z appended. If no file is specified, compress standard input. Each file specified is compressed separately. compress ignores files that are symbolic links. See also gzip.

Options

• -b maxbits
• Limit the maximum number of bits.
• -c
• Write output to standard output, not to a Z file.
• -d
• Decompress instead of compressing. Same as uncompress.
• -f
• Force generation of an output file even if one already exists.
• -r
• If any of the specified files is a directory, compress recursively.
• -v
• Print compression statistics.
• -V
• Print version and compilation information and then exit.

cp [options] files directory

Copy file1 to file2, or copy one or more files to the same names under directory. If the destination is an existing file, the file is overwritten; if the destination is an existing directory, the file is copied into the directory (the directory is not overwritten).

Options

• -a, --archive
• Preserve attributes of original files where possible. Same as -dpR.
• -b, --backup
• Back up files that would otherwise be overwritten.
• -d, --no-dereference
• Do not dereference symbolic links; preserve hard link relationships between source and copy.
• -f, --force
• Remove existing files in the destination.
• -i, --interactive
• Prompt before overwriting destination files.
• -l, --link
• Make hard links, not copies, of nondirectories.
• -p, --preserve
• Preserve all information, including owner, group, permissions, and timestamps.
• -P, --parents
• Preserve intermediate directories in source. The last argument must be the name of an existing directory. For example, the command:
  
  

  cp --parents jphekman/tutorial/ch1 newdir
  

  
  
  copies the file jphekman/tutorial/ch1 to the file newdir/jphekman/tutorial/ch1, creating intermediate directories as necessary.
• -r, -R, --recursive
• Copy directories recursively.
• -S backup-suffix, --suffix=backup-suffix
• Set suffix to be appended to backup files. This may also be set with the SIMPLE_BACKUP_SUFFIX environment variable. The default is ~. You need to explicitly include a period if you want one before the suffix (e.g., specify bak, not bak).
• -s, --symbolic-link
• Make symbolic links instead of copying. Source filenames must be absolute.
• -u, --update
• Do not copy a file to an existing destination with the same or newer modification time.
• -v, --verbose
• Before copying, print the name of each file.
• -V type, --version-control=type
• Set the type of backups made. You may also use the VERSION_CONTROL environment variable. The default is existing. Valid arguments are:
  • t, numbered
  • Always make numbered backups.
  • nil, existing
  • Make numbered backups of files that already have them; otherwise, make simple backups.
  • never, simple
  • Always make simple backups.
• -x, --one-file-system
• Ignore subdirectories on other filesystems.

Copy file archives in from or out to tape or disk, or to another location on the local machine. Each of the three flags -i, -o, or -p accepts different options.

Flags

• -i, --extract [options] [patterns]
• Copy in (extract) from an archive files whose names match selected patterns. Each pattern can include Bourne shell filename metacharacters. (Patterns should be quoted or escaped so they are interpreted by cpio, not by the shell.) If pattern is omitted, all files are copied in. Existing files are not overwritten by older versions from the archive unless -u is specified.
• -o, --create [options]
• Copy out to an archive a list of files whose names are given on the standard input.
• -p, --pass-through [options] directory
• Copy (pass) files to another directory on the same system. Destination pathnames are interpreted relative to the named directory.

Comparison of valid options

Options available to the -i, -o, and -p flags are shown here. (The - is omitted for clarity):

i: bcdf mnrtsuv B SVCEHMR IF o: 0a c vABL VC HM O F p: 0a d lm uv L V R

Options

• -0, --null
• Expect list of filenames to be terminated with null, not newline. This allows files with a newline in their names to be included.
• -a, --reset-access-time
• Reset access times of input files after reading them.
• -A, --append
• Append files to an existing archive, which must be a disk file. Specify this archive with -O or -F.
• -b, --swap
• Swap bytes and half-words to convert between big-endian and little-endian 32-bit integers.
• -B
• Block input or output using 5120 bytes per record (default is 512 bytes per record).
• --blocksize=size
• Set input or output blocksize to size × 512 bytes.
• -c
• Read or write header information as ASCII characters; useful when source and destination machines are different types.
• -C n, --io-size=n
• Like -B, but blocksize can be any positive integer n.
• -d, --make-directories
• Create directories as needed.
• -E file, --pattern-file=file
• Extract filenames from the archives that match patterns in file.
• -f, --nonmatching
• Reverse the sense of copying; copy all files except those that match patterns.
• -F file, --file=file
• Use file as the archive, not stdin or stdout. file can reside on another machine, if given in the form user@hostname:file (where user@ is optional).
• --force-local
• Assume that file (provided by -F, -I, or -O) is a local file, even if it contains a colon (:) indicating a remote file.
• -H type, --format=type
• Use type format. Default for copy-out is bin; for copy-in the default is autodetection of the format. Valid formats (all caps also accepted) are:
  • bin
  • Binary
  • odc
  • Old (POSIX.1) portable format
  • newc
  • New (SVR4) portable format
  • crc
  • New (SVR4) portable format with checksum added
  • tar
  • Tar
  • ustar
  • POSIX.1 tar (also recognizes GNU tar archives)
  • hpbin
  • HP-UX's binary (obsolete)
  • hpodc
  • HP-UX's portable format
• -I file
• Read file as an input archive. May be on a remote machine (see -F).
• -k
• Ignored. For backward compatibility.
• -l, --link
• Link files instead of copying.
• -L, --dereference
• Follow symbolic links.
• -m, --preserve-modification-time
• Retain previous file modification time.
• -M msg, --message=msg
• Print msg when switching media, as a prompt before switching to new media. Use variable %d in the message as a numeric ID for the next medium. -M is valid only with -I or -O.
• -n, --numeric-uid-gid
• When verbosely listing contents, show user ID and group ID numerically.
• --no-absolute-filenames
• Create all copied-in files relative to the current directory.
• --no-preserve-owner
• Make all copied files owned by yourself, instead of the owner of the original. Useful only if you are a privileged user.
• -O file
• Archive the output to file, which may be a file on another machine (see -F).
• --only-verify-crc
• For a CRC-format archive, verify the CRC of each file; don't actually copy the files in.
• --quiet
• Don't print the number of blocks copied.
• -r
• Rename files interactively.
• -R [user][:group], --owner [user][:group]
• Reassign file ownership and group information to the user's login ID (privileged users only).
• -s, --swap-bytes
• Swap bytes of each two-byte half-word.
• -S, --swap-half-words
• Swap half-words of each four-byte word.
• --sparse
• For copy-out and copy-pass, write files that have large blocks of zeros as sparse files.
• -t, --list
• Print a table of contents of the input (create no files). When used with the -v option, resembles output of ls -l.
• -u, --unconditional
• Unconditional copy; old files can overwrite new ones.
• -v, --verbose
• Print a list of filenames processed.
• -V, --dot
• Print a dot for each file read or written (this shows cpio at work without cluttering the screen).
• --version
• Print version number and then exit.

Examples

Generate a list of files whose names end in old using find; use list as input to cpio:

find . -name "*.old" -print | cpio -ocBv > /dev/rst8

Restore from a tape drive all files whose names contain save (subdirectories are created if needed):

cpio -icdv "*save*" < /dev/rst8

Move a directory tree:

find . -depth -print | cpio -padm /mydir

System administration command. Normally started in a system startup file. Execute commands at scheduled times, as specified in users' files in /var/cron/tabs. Each file shares its name with the user who owns it. The files are controlled via the command crontab.

View, install, or uninstall your current crontab file. A privileged user can run crontab for another user by supplying -u user. A crontab file is a list of commands, one per line, that will execute automatically at a given time. Numbers are supplied before each command to specify the execution time. The numbers appear in five fields, as follows:

Minute
 0-59 
Hour
 0-23 
Day of month
 1-31 
Month
 1-12 Jan, Feb, Mar, ... 
Day of week
 0-6, with 0 = Sunday Sun, Mon, Tue, ...

Use a comma between multiple values, a hyphen to indicate a range, and an asterisk to indicate all possible values. For example, assuming these crontab entries:

* * 5 find / -print | backup_program 0 0 1,15 * * echo "Timesheets due" | mail user

The first command backs up the system files every Friday at 3:59 a.m., and the second command mails a reminder on the 1st and 15th of each month.

The superuser can always issue the crontab command. Other users must be listed in the file /etc/cron.allow if it exists; otherwise, they must not be listed in /etc/cron.deny. If neither file exists, only the superuser can issue the command.

Options

The -e, -l, and -r options are not valid if any files are specified.

• -e
• Edit the user's current crontab file (or create one).
• -l
• Display the user's crontab file on standard output.
• -r
• Delete the user's crontab file.
• -u user
• Indicates which user's crontab file will be acted upon.

C shell, a command interpreter into which all other commands are entered. For more information, see "csh and tcsh".

Separate file into context-based sections and place sections in files named xx00 through xxn (n < 100), breaking file at each pattern specified in arguments. See also split.

Options

• -
• Read from standard input.
• -b suffix, --suffix-format=suffix
• Append suffix to output filename. This option causes -n to be ignored. suffix must specify how to convert the binary integer to readable form by including exactly one of the following: %d, %i, %u, %o, %x, or %X. The value of suffix determines the format for numbers as follows:
  • %d
  • Signed decimal
  • %i
  • Same as %d
  • %u
  • Unsigned decimal
  • %o
  • Octal
  • %x
  • Hexadecimal
  • %X
  • Same as %x.
• -f prefix, --prefix=prefix
• Name new files prefix through prefixn (default is xx00 through xxn).
• -k, --keep-files
• Keep newly created files, even when an error occurs (which would normally remove these files). This is useful when you need to specify an arbitrarily large repeat argument, {n}, and you don't want an out-of-range error to cause removal of the new files.
• -n num, --digits=num
• Use output filenames with numbers num digits long. The default is 2.
• -s, -q, --silent, --quiet
• Suppress all character counts.
• -z, --elide-empty-files
• Do not create empty output files. However, number as if those files had been created.

Arguments

Any one or a combination of the following expressions may be specified as arguments. Arguments containing blanks or other special characters should be surrounded by single quotes.

• /expr/[offset]
• Create file from the current line up to the line containing the regular expression expr. offset should be of the form +n or -n, where n is the number of lines below or above expr.
• %expr%[offset]
• Same as /expr/ except no file is created for lines previous to line containing expr.
• num
• Create file from current line up to (but not including) line number num. When followed by a repeat count (number inside {}), put the next num lines of input into another output file.
• {n}
• Repeat argument n times. May follow any of the preceding arguments. Files will split at instances of expr or in blocks of num lines. If * is given instead of n, repeat argument until input is exhausted.

Examples

Create up to 20 chapter files from the file novel:

csplit -k -f chap. novel '/CHAPTER/' '{20}'

Create up to 100 address files (xx00 through xx99), each four lines long, from a database named address_list:

csplit -k address_list 4 {99}

Create a list of function and macro names that are defined in the specified C, C++, FORTRAN, Java, Perl, yacc, or other source files. The output list (named tags by default) contains lines of the form:

name file context

where name is the function or macro name, file is the source file in which name is defined, and context is a search pattern that shows the line of code containing name. After the list of tags is created, you can invoke vi on any file and type:

:set tags=tagsfile :tag name

This switches the vi editor to the source file associated with the name listed in tagsfile (which you specify with -t).

etags produces an equivalent file for tags to be used with Emacs.

Options

• -a, --append
• Append tag output to existing list of tags.
• -d, --defines
• Include tag entries for C preprocessor definitions.
• -i file, --include=file
• Add a note to the tags file that file should be consulted in addition to the normal input file.
• -l language, --language=language
• Consider the files that follow this option to be written in language. Use the -h option for a list of languages and their default filename extensions.
• -o file, --output=file
• Write to file.
• -rregexp, --regex=regexp
• Include a tag for each line that matches regexp in the files following this option.
• -R, --no-regex
• Don't include tags based on regular-expression matching for the files that follow this option.
• -t, --typedefs
• Include tag entries for typedefs.
• -u, --update
• Update tags file to reflect new locations of functions (e.g., when functions are moved to a different source file). Old tags are deleted; new tags are appended.
• -v, --vgrind
• Print to standard output a listing (index) of each function, source file, and page number (1 page = 64 lines).
• -w, --no-warn
• Suppress warning messages.
• -x, --cxref
• Produce a listing of each function, and its line number, source file, and context.
• -B, --backward-search
• Search for tags backward through files.
• -C, --c++
• Expect c and h files to contain C++, not C, code.
• -H, -h, --help
• Print usage information and exit.
• -S, --ignore-indentation
• Normally ctags uses indentation to parse the tag file; this option tells it to rely on it less.
• -T, --typedefs-and-c++
• Include tag entries for typedefs, structs, enums, unions, and C++ member functions.
• -V, --version
• Print the version number and exit.

Cut out selected columns or fields from one or more files. In the following options, list is a sequence of integers. Use a comma between separate values and a hyphen to specify a range (e.g., -10,, or -). See also paste and join.

Options

• -b list, --bytes list
• Specify list of positions; only bytes in these positions will be printed.
• -c list, --characters list
• Cut the column positions identified in list.
• -d c, --delimiter c
• Use with -f to specify field delimiter as character c (default is tab); special characters (e.g., a space) must be quoted.
• -f list, --fields list
• Cut the fields identified in list.
• -n
• Don't split multibyte characters.
• -s, --only-delimited
• Use with -f to suppress lines without delimiters.
• --output-delimiter=string
• Use string as the output delimiter. By default, the output delimiter is the same as the input delimiter.
• --help
• Print help message and then exit.
• --version
• Print version information and then exit.

Examples

Extract usernames and real names from /etc/passwd:

cut -d: -f1,5 /etc/passwd

Find out who is logged on, but list only login names:

who | cut -d"" -f1

Cut characters in the fourth column of file, and paste them back as the first column in the same file:

cut -c4 file | paste - file

Print the current date and time. You may specify a display format. format can consist of literal text strings (blanks must be quoted) as well as field descriptors, whose values will appear as described in the following entries (the listing shows some logical groupings). A privileged user can change the system's date and time.

Options

• +format
• Display current date in a nonstandard format. For example:
  
  

  % date +"%A %j %n%k %p" Tuesday 248 15 PM
  

  The default is %a %b %e %T %Z %Y -- e.g., Tue Sep 5 14:59:37 EDT 2000.

• -d date, --date date
• Display date, which should be in quotes and may be in the format d days or m months d days to print a date in the future. Specify ago to print a date in the past. You may include formatting (see the "Format" section that follows).
• -f datefile, --file=datefile
• Like -d but printed once for each line of datefile.
• -I [timespec], --iso-8601[=timespec]
• Display in ISO-8601 format. If specified, timespec can have one of the values date (for date only), hours, minutes, or seconds to get the indicated precision.
• -r file, --reference=file
• Display the time file was last modified.
• -R, --rfc-822
• Display the date in RFC 822 format.
• --help
• Print help message and exit.
• --version
• Print version information and exit.
• -s date, --set date
• Set the date.
• -u, --universal
• Set the date to Greenwich Mean Time, not local time.

Format

• %
• Literal %.
• -
• Do not pad fields (default: pad fields with zeros).
• _
• Pad fields with space (default: zeros).
• %a
• Abbreviated weekday.
• %b
• Abbreviated month name.
• %c
• Country-specific date and time format.
• %d
• Day of month (01-31).
• %h
• Same as %b.
• %j
• Julian day of year (001-366).
• %k
• Hour in 24-hour format, without leading zeros (0-23).
• %l
• Hour in 12-hour format, without leading zeros (1-12).
• %m
• Month of year (01-12).
• %n
• Insert a new line.
• %p
• String to indicate AM or PM.
• %r
• Time in %I:%M:%S %p (12-hour) format.
• %s
• Seconds since "The Epoch," 1970-01-01 00:00:00 UTC (a nonstandard extension).
• %t
• Insert a tab.
• %w
• Day of week (Sunday = 0).
• %x
• Country-specific date format.
• %y
• Last two digits of year (00-99).
• %z
• RFC 822-style numeric time zone.
• %A
• Full weekday.
• %B
• Full month name.
• %D
• Date in %m/%d/%y format.
• %H
• Hour in 24-hour format (00-23).
• %I
• Hour in 12-hour format (01-12).
• %M
• Minutes (00-59).
• %S
• Seconds (00-59).
• %T
• Time in %H:%M:%S format.
• %U
• Week number in year (00-53); start week on Sunday.
• %V
• Week number in year (01-52); start week on Monday.
• %W
• Week number in year (00-53); start week on Monday.
• %X
• Country-specific time format.
• %Y
• Four-digit year (e.g., 1996).
• %Z
• Time zone name.

Strings for setting date

Strings for setting the date may be numeric or nonnumeric. Numeric strings consist of time, day, and year in the format MMDDhhmm[[CC]YY][.ss]. Nonnumeric strings may include month strings, time zones, a.m., and p.m.

• time
• A two-digit hour and two-digit minute (hhmm); hh uses 24-hour format.
• day
• A two-digit month and two-digit day of month (MMDD); default is current day and month.
• year
• The year specified as either the full four-digit century and year or just the two-digit year; the default is the current year.

Examples

Set the date to July 1 (), 4 a.m. (), 1995 ():

date 0701040095

The command:

date +"Hello%t Date is %D %n%t Time is %T"

produces a formatted date as follows:

 Hello Date is 05/09/93 Time is 17:53:39

Make a copy of an input file (if) using the specified conditions, and send the results to the output file (or standard output if of is not specified). Any number of options can be supplied, although if and of are the most common and are usually specified first. Because dd can handle arbitrary blocksizes, it is useful when converting between raw physical devices.

Options

• bs=n
• Set input and output blocksize to n bytes; this option overrides ibs and obs.
• cbs=n
• Set the size of the conversion buffer (logical record length) to n bytes. Use only if the conversion flag is ascii, ebcdic, ibm, block, or unblock.
• conv=flags
• Convert the input according to one or more (comma-separated) flags listed next. The first five flags are mutually exclusive.
  • ascii
  • EBCDIC to ASCII.
  • ebcdic
  • ASCII to EBCDIC.
  • ibm
  • ASCII to EBCDIC with IBM conventions.
  • block
  • Variable-length records (i.e., those terminated by a newline) to fixed-length records.
  • unblock
  • Fixed-length records to variable-length.
  • lcase
  • Uppercase to lowercase.
  • ucase
  • Lowercase to uppercase.
  • noerror
  • Continue processing after read errors.
  • notrunc
  • Don't truncate output file.
  • swab
  • Swap each pair of input bytes.
  • sync
  • Pad input blocks to ibs with trailing zeros.
• count=n
• Copy only n input blocks.
• ibs=n
• Set input blocksize to n bytes (default is 512).
• if=file
• Read input from file (default is standard input).
• obs=n
• Set output blocksize to n bytes (default is 512).
• of=file
• Write output to file (default is standard output).
• seek=n
• Skip n output-sized blocks from start of output file.
• skip=n
• Skip n input-sized blocks from start of input file.
• --help
• Print help message and then exit.
• --version
• Print the version number and then exit.

You can multiply size values (n) by a factor of 1024, 512, or 2 by appending the letter k, b, or w, respectively. You can use the letter x as a multiplication operator between two numbers.

Examples

Convert an input file to all lowercase:

dd if=caps_file of=small_file conv=lcase

Retrieve variable-length data; write it as fixed-length to out:

data_retrieval_cmd | dd of=out conv=sync,block

System administration command. Debug an ext2 filesystem. device is the special file corresponding to the device containing the ext2 filesystem (e.g., /dev/hda3).

Option

• -w
• Open the filesystem read-write.

Commands

• cat file
• Dump the contents of an inode to standard output.
• cd directory
• Change the current working directory to directory.
• chroot directory
• Change the root directory to be the specified inode.
• close
• Close the currently open filesystem.
• clri file
• Clear the contents of the inode corresponding to file.
• dump file out_file
• Dump the contents of an inode to out_file.
• expand_dir directory
• Expand directory.
• find_free_block [goal]
• Find first free block starting from goal (if specified) and allocate it.
• find_free_inode [dir [mode]]
• Find a free inode and allocate it.
• freeb block
• Mark block as not allocated.
• freei file
• Free the inode corresponding to file.
• help
• Print a list of commands understood by debugfs.
• icheck block
• Do block-to-inode translation.
• initialize device blocksize
• Create an ext2 filesystem on device.
• kill_file file
• Remove file and deallocate its blocks.
• ln source_file dest_file
• Create a link.
• ls [pathname]
• Emulate the ls command.
• modify_inode file
• Modify the contents of the inode corresponding to file.
• mkdir directory
• Make directory.
• mknod file [p|[[c|b] major minor]]
• Create a special device file.
• ncheck inode
• Do inode-to-name translation.
• open [-w] device
• Open a filesystem.
• pwd
• Print the current working directory.
• quit
• Quit debugfs.
• rm file
• Remove file.
• rmdir directory
• Remove directory.
• setb block
• Mark block as allocated.
• seti file
• Mark in use the inode corresponding to file.
• show_super_stats
• List the contents of the super block.
• stat file
• Dump the contents of the inode corresponding to file.
• testb block
• Test whether block is marked as allocated.
• testi file
• Test whether the inode corresponding to file is marked as allocated.
• unlink file
• Remove a link.
• write source_file file
• Create a file in the filesystem named file, and copy the contents of source_file into the destination file.

System administration command. Create a dependency file for the modules given on the command line. This dependency file can be used by modprobe to automatically load the relevant modules. The normal use of depmod is to include the line /sbin/depmod -a in one of the files in /etc/rc.d so the correct module dependencies will be available after booting the system.

Options

• -a
• Create dependencies for all modules listed in /etc/conf.modules.
• -d
• Debug mode. Show all commands being issued.
• -e
• Print a list of all unresolved symbols.
• -v
• Print a list of all processed modules.

Files

• /etc/conf.modules
• Information about modules: which ones depend on others, and which directories correspond to particular types of modules.
• /sbin/insmod, /sbin/rmmod
• Programs that depmod relies on.

Report the amount of free disk space available on all mounted filesystems or on the given name. (df cannot report on unmounted filesystems.) Disk space is shown in 1KB blocks (default) or 512-byte blocks (if the environment variable POSIXLY_CORRECT is set). name can be a device name (e.g., /dev/hd*), the directory name of a mounting point (e.g., /usr), or a directory name (in which case df reports on the entire filesystem in which that directory is mounted).

Options

• -a, --all
• Include empty filesystems (those with 0 blocks).
• --block-size=n
• Show space as n-byte blocks.
• -h, --human-readable
• Print sizes in a format friendly to human readers (e.g., 1.9G instead of 1967156).
• -H, --si
• Like -h, but show as power of 1000 rather than 1024.
• -i, --inodes
• Report free, used, and percent-used inodes.
• -k, --kilobytes
• Print sizes in kilobytes.
• -l, --local
• Show local filesystems only.
• -m, --megabytes
• Print sizes in megabytes.
• --no-sync
• Show results without invoking sync first (i.e., without flushing the buffers). This is the default.
• -P, --portability
• Use POSIX output format (i.e., print information about each filesystem on exactly one line).
• --sync
• Invoke sync (flush buffers) before getting and showing sizes.
• -t type, --type=type
• Show only type filesystems.
• -T, --print-type
• Print the type of each filesystem in addition to the sizes.
• -x type, --exclude-type=type
• Show only filesystems that are not of type type.
• --help
• Print help message and then exit.
• --version
• Print the version and then exit.

Compare two text files. diff reports lines that differ between file1 and file2. Output consists of lines of context from each file, with file1 text flagged by a < symbol and file2 text by a > symbol. Context lines are preceded by the ed command (a, c, or d) that would be used to convert file1 to file2. If one of the files is -, standard input is read. If one of the files is a directory, diff locates the filename in that directory corresponding to the other argument (e.g., diff my_dir junk is the same as diff my_dir/junk junk). If both arguments are directories, diff reports lines that differ between all pairs of files having equivalent names (e.g., olddir/program and newdir/program); in addition, diff lists filenames unique to one directory, as well as subdirectories common to both. See also cmp.

Options

• -a, --text
• Treat all files as text files. Useful for checking to see if binary files are identical.
• -b, --ignore-space-change
• Ignore repeating blanks and end-of-line blanks; treat successive blanks as one.
• -B, --ignore-blank-lines
• Ignore blank lines in files.
• -c
• Context diff: print 3 lines surrounding each changed line.
• -C n, --context[=n]
• Context diff: print n lines surrounding each changed line. The default context is 3 lines.
• -d, --minimal
• To speed up comparison, ignore segments of numerous changes and output a smaller set of changes.
• -Dsymbol, --ifdef=symbol
• When handling C files, create an output file that contains all the contents of both input files, including #ifdef and #ifndef directives that reflect the directives in both files.
• -e, --ed
• Produce a script of commands (a, c, d) to re-create file2 from file1 using the ed editor.
• -F regexp, --show-function-line[=regexp]
• For context and unified diff, show the most recent line containing regexp before each block of changed lines.
• -H
• Speed output of large files by scanning for scattered small changes; long stretches with many changes may not show up.
• --help
• Print brief usage message.
• --horizon-lines=n
• In an attempt to find a more compact listing, keep n lines on both sides of the changed lines when performing the comparison.
• -i, --ignore-case
• Ignore case in text comparison. Uppercase and lowercase are considered the same.
• -I regexp, --ignore-matching-lines=regexp
• Ignore lines in files that match the regular expression regexp.
• -l, --paginate
• Paginate output by passing it to pr.
• -L label, --label label, --label=label
• For context and unified diff, print label in place of the filename being compared. The first such option applies to the first filename and the second option to the second filename.
• --left-column
• For two-column output (-y), show only left column of common lines.
• -n, --rcs
• Produce output in RCS diff format.
• -N, --new-file
• Treat nonexistent files as empty.
• -p, --show-c-function
• When handling files in C or C-like languages such as Java, show the function containing each block of changed lines. Assumes -c but can also be used with a unified diff.
• -P, --unidirectional-new-file
• If two directories are being compared and the first lacks a file that is in the second, pretend that an empty file of that name exists in the first directory.
• -q, --brief
• Output only whether files differ.
• -r, --recursive
• Compare subdirectories recursively.
• -s, --report-identical-files
• Indicate when files do not differ.
• -S filename, --starting-file=filename
• For directory comparisons, begin with the file filename, skipping files that come earlier in the standard list order.
• --suppress-common-lines
• For two-column output (-y), do not show common lines.
• -t, --expand-tabs
• Produce output with tabs expanded to spaces.
• -T, --initial-tab
• Insert initial tabs into output to line up tabs properly.
• -u
• Unified diff: print old and new versions of lines in a single block, with 3 lines surrounding each block of changed lines.
• -U n, --unified[=n]
• Unified diff: print old and new versions of lines in a single block, with n lines surrounding each block of changed lines. The default context is 3 lines.
• -v, --version
• Print version number of this version of diff.
• -w, --ignore-all-space
• Ignore all whitespace in files for comparisons.
• -W n, --width=n
• For two-column output (-y), produce columns with a maximum width of n characters. Default is 130.
• -x regexp, --exclude=regexp
• Do not compare files in a directory whose names match regexp.
• -X filename, --exclude-from=filename
• Do not compare files in a directory whose names match patterns described in the file filename.
• -y, --side-by-side
• Produce two-column output.
• -n
• For context and unified diff, print n lines of context. Same as specifying a number with -C or -U.

Compare 3 files and report the differences. No more than one of the files may be given as - (indicating that it is to be read from standard input). The output is displayed with the following codes:

• ====
• All three files differ.
• ====1
• file1 is different.
• ====2
• file2 is different.
• ====3
• file3 is different.

diff3 is also designed to merge changes in two differing files based on a common ancestor file (i.e., when two people have made their own set of changes to the same file). diff3 can find changes between the ancestor and one of the newer files and generate output that adds those differences to the other new file. Unmerged changes are places where both of the newer files differ from each other and at least one of them from the ancestor. Changes from the ancestor that are the same in both of the newer files are called merged changes. If all three files differ in the same place, it is called an overlapping change.

This scheme is used on the command line with the ancestor being file2, the second filename. Comparison is made between file2 and file3, with those differences then applied to file1.

Options

• -3, --easy-only
• Create an ed script to incorporate into file1 unmerged, nonoverlapping differences between file1 and file3.
• -a, --text
• Treat files as text.
• -A, --show-all
• Create an ed script to incorporate all changes, showing conflicts in bracketed format.
• -e, --ed
• Create an ed script to incorporate into file1 all unmerged differences between file2 and file3.
• -E, --show-overlap
• Create an ed script to incorporate unmerged changes, showing conflicts in bracketed format.
• -x, --overlap-only
• Create an ed script to incorporate into file1 all differences where all three files differ (overlapping changes).
• -X
• Same as -x, but show only overlapping changes, in bracketed format.
• -m, --merge
• Create file with changes merged (not an ed script).
• -L label, --label=label
• Use label to replace filename in output.
• -i
• Append the w (save) and q (quit) commands to ed script output.
• -T, --initial-tab
• Begin lines with a tab instead of two spaces in output to line tabs up properly.
• -v, --version
• Print version information and then exit.

System administration command. Set up or initiate dial-up Internet connections. dip can be used to establish connections for users dialing out or dialing in. Commands can be used in interactive mode or placed in a script file for use in dial-out connections. To establish dial-in connections, dip is often is used as a shell and may be executed using the commands diplogin or diplogini.

Options

• -a
• In dial-in mode, prompt for username and password. Same as the diplogini command.
• -i
• Initiate a login shell for a dial-in connection. Same as the diplogin command.
• -k
• Kill the most recent dip process or the process running on the device specified by the -l option.
• -l device
• Used with the -k option. Specifies a tty device.
• -m mtu
• Maximum Transfer Unit. The default is 296.
• -p protocol
• The protocol to use: SLIP, CSLIP, PPP, or TERM.
• -t
• Command mode. This is usually done for testing.
• -v
• Verbose mode.

Commands

Most of these commands can be used either in interactive mode or in a script file.

• beep times
• Beep the terminal the specified number of times.
• bootp
• Retrieve local and remote IP addresses using the BOOTP protocol.
• break
• Send a BREAK.
• chatkey keyword code
• Map a modem response keyword to a numeric code.
• config [interface|routing] [pre|up|down|post] arguments
• Modify interface characteristics or the routing table, before the link comes up, when it is up, when it goes down, or after it is down. The syntax for arguments is the same as arguments for the ifconfig or route commands.
• databits |
• Set the number of data bits.
• dec $variable [value]
• Decrement $variable by value. The default is 1.
• default
• Set default route to the IP address of the host connected to.
• dial phonenumber [timeout]
• Dial phonenumber. Abort if remote modem doesn't answer within timeout seconds. Set $errlvl according to the modem response.
• echo on|off
• Enable or disable the display of modem commands.
• exit [n]
• Exit the script. Optionally return the number n as the exit status.
• flush
• Clear the input buffer.
• get $variable [ask|remote [timeout]] value
• Set $variable to value. If ask is specified, prompt the user for a value. If remote is specified, retrieve the value from the remote system. Abort after timeout seconds.
• goto label
• Jump to the section identified by label.
• help
• List available commands.
• if expr goto label
• Jump to the section identified by label if the expression evaluates to true. An expression compares a variable to a constant using one of these operators: =, !=, <, >, <=, or >=.
• inc $variable [value]
• Increment $variable by value. The default is 1.
• init string
• Set the string used to initialize the modem. The default is ATE0 Q0 V1 X1.
• mode protocol
• Set the connection protocol. Valid values are SLIP, CSLIP, PPP, and TERM. The default is SLIP.
• netmask mask
• Set the subnet mask.
• parity E|O|N
• Set the line parity to even, odd, or none.
• password
• Prompt user for password.
• proxyarp
• Install a proxy ARP entry in the local ARP table.
• print $variable
• Display the content of $variable.
• psend command
• Execute command in a shell, and send output to the serial device. Commands are executed using the user's real UID.
• port device
• Specify the serial device the modem is attached to.
• quit
• Exit with a nonzero exit status. Abort the connection.
• reset
• Reset the modem.
• securid
• Prompt user for the variable part of an ACE System SecureID password and send it together with the stored prefix to the remote system.
• securidf prefix
• Store the fixed part of an ACE System SecureID password.
• send string
• Send string to the serial device.
• shell command
• Execute command in a shell using the user's real UID.
• skey [timeout]
• Wait for an S/Key challenge, then prompt user for the secret key. Generate and send the response. Abort if challenge is not received within timeout seconds. S/Key support must be compiled into dip.
• sleep time
• Wait time seconds.
• speed bits-per-second
• Set the port speed. Default is 38400.
• stopbits |
• Set the number of stop bits.
• term
• Enable terminal mode. Pass keyboard input directly to the serial device.
• timeout time
• Set the number of seconds the line can be inactive before the link is closed.
• wait text [timeout]
• Wait timeout seconds for text to arrive from the remote system. If timeout is not specified, wait forever.

Print pathname excluding the last level. Useful for stripping the actual filename from a pathname. If there are no slashes (no directory levels) in pathname, dirname prints to indicate the current directory. See also basename.

System administration command. Display the system control messages from the kernel ring buffer. This buffer stores all messages since the last system boot or the most recent ones, if the buffer has been filled.

Options

• -c
• Clear buffer after printing messages.
• -n level
• Set the level of system message that will display on console.

TCP/IP command. Print the system's DNS domain name. See also hostname.

NFS/NIS command. Set or display name of current NIS domain. With no argument, domainname displays the name of the current NIS domain. Only a privileged user can set the domain name by giving an argument; this is usually done in a startup script.

fsck.ext2 [options] device

System administration command. Similar to fsck, but specifically intended for MS-DOS filesystems. When checking an MS-DOS filesystem, fsck calls this command. Normally dosfsck stores all changes in memory, then writes them when checks are complete.

Options

• -a
• Automatically repair the system; do not prompt the user.
• -A
• Use the Atari version of the MS-DOS filesystem.
• -d file
• Drop the named file from the file allocation table. Force checking, even if kernel has already marked the filesystem as valid. dosfsck will normally exit without checking if the system appears to be clean.
• -l file
• Consult file for a list of bad blocks, in addition to checking for others.
• -n
• Ensure that no changes are made to the filesystem. When queried, answer "no."
• -p
• "Preen." Repair all bad blocks noninteractively.
• -t
• Display timing statistics.
• -v
• Verbose.
• -y
• When queried, answer "yes."
• -B size
• Expect to find the superblock at size; if it's not there, exit.
• -F
• Flush buffer caches before checking.
• -L file
• Consult file for list of bad blocks instead of checking filesystem for them.

Print disk usage (as the number of 1KB blocks used by each named directory and its subdirectories; default is current directory).

Options

• -a, --all
• Print usage for all files, not just subdirectories.
• -b, --bytes
• Print sizes in bytes.
• -c, --total
• In addition to normal output, print grand total of all arguments.
• -D, --dereference-args
• Follow symbolic links, but only if they are command-line arguments.
• -h, --human-readable
• Print sizes in human-reader-friendly format.
• -H, --si
• Like -h, but show as power of 1000 rather than 1024.
• -k, --kilobytes
• Print sizes in kilobytes (this is the default).
• -l, --count-links
• Count the size of all files, whether or not they have already appeared (i.e., via a hard link).
• -L, --dereference
• Follow symbolic links.
• --exclude=pattern
• Exclude files that match pattern.
• --max-depth=num
• Report sizes for directories only down to num levels below the starting point (which is level 0).
• -m, --megabytes
• Print sizes in megabytes.
• -s, --summarize
• Print only the grand total for each named directory.
• -S, --separate-dirs
• Do not include the sizes of subdirectories when totaling the size of parent directories.
• -x, --one-file-system
• Display usage of files in current filesystem only.
• -X, --exclude-from=file
• Exclude files that match any pattern in file.
• --help
• Print help message and then exit.
• --version
• Print the version and then exit.

System administration command. Print information about device's superblock and blocks group.

Print information about the keyboard driver's translation tables to standard output. Further information is available in the manual pages under keytables.

Options

• -1, --separate-lines
• Print one line for each modifier/keycode pair and prefix plain to each unmodified keycode.
• -ccharset, --charset=charset
• Specify character set with which to interpret character code values. The default character set is iso-8859-1. The full list of valid character sets is available with the --help option.
• --compose-only
• Print compose key combinations only. Requires compose key support in the kernel.
• -f, --full-table
• Output in canonical, not short, form: for each key, print a row with modifier combinations divided into columns.
• --funcs-only
• Print function key string definitions only; do not print key bindings or string definitions.
• -h, --help
• Print help message and the version.
• -i, --short-info
• Print in short-info format, including information about acceptable keycode keywords in the keytable files; the number of actions that can be bound to a key; a list of the ranges of action codes (the values to the right of a key definition); and the number of function keys that the kernel supports.
• --keys-only
• Print key bindings only; do not print string definitions.
• -l, --long-info
• Print the same information as in --short-info, plus a list of the supported action symbols and their numeric values.
• -n, --numeric
• Print action code values in hexadecimal notation; do not attempt to convert them to symbolic notation.
• -S num, --shape=num
• Print using num to determine table shape. Values of num are:
  • Default
  • Same as --full-table
  • Same as --separate-lines
  • One line for each keycode up to the first hole, then one line per modifier/keycode pair

fsck.ext2 [options] device

System administration command. Similar to fsck, but specifically intended for Linux Second Extended Filesystems. When checking a second extended filesystem, fsck calls this command.

Options

• -b superblock
• Use superblock instead of default superblock.
• -d
• Debugging mode.
• -f
• Force checking, even if kernel has already marked the filesystem as valid. e2fsck will normally exit without checking if the system appears to be clean.
• -l file
• Consult file for a list of bad blocks, in addition to checking for others.
• -n
• Ensure that no changes are made to the filesystem. When queried, answer "no."
• -p
• "Preen." Repair all bad blocks noninteractively.
• -t
• Display timing statistics.
• -v
• Verbose.
• -y
• When queried, answer "yes."
• -B size
• Expect to find the superblock at size; if it's not there, exit.
• -F
• Flush buffer caches before checking.
• -L file
• Consult file for list of bad blocks instead of checking filesystem for them.

This is the /bin/echo command. echo also exists as a command built into the C shell and bash. The following character sequences have special meanings:

• a
• Alert (bell)
• b
• Backspace
• c
• Suppress trailing newline
• f
• Form feed
• n
• Newline
• r
• Carriage return
• t
• Horizontal tab
• v
• Vertical tab
• Literal backslash
• nnn
• The octal character whose ASCII code is nnn.

Options

• -e
• Enable character sequences with special meaning. (In some versions, this option is not required in order to make the sequences work.)
• -E
• Disable character sequences with special meaning.
• -n
• Suppress printing of newline after text.
• --help
• Print help message and then exit.
• --version
• Print version information and then exit.

Examples

/bin/echo "testing printer" | lp /bin/echo "TITLE\nTITLE" > file ; cat doc1 doc2 >> file /bin/echo "Warning: ringing bell \a"

Search one or more files for lines that match an extended regular expression regexp. egrep doesn't support the regular expressions \(, \), \n, \<, \>, \{, or \} but does support the other expressions, as well as the extended set +, ?, |, and ( ). Remember to enclose these characters in quotes. Regular expressions are described in "Pattern Matching". Exit status is 0 if any lines match, 1 if none match, and 2 for errors.

See grep for the list of available options. Also see fgrep. egrep typically runs faster than those commands.

Examples

Search for occurrences of Victor or Victoria in file:

egrep 'Victor(ia)*' file egrep '(Victor|Victoria)' file

Find and print strings such as old.doc1 or new.doc2 in files, and include their line numbers:

egrep -n '(old|new)\.doc?' files

A text editor and all-purpose work environment. For more information, see "The Emacs Editor".

Display the current environment or, if an environment variable is specified, set it to a new value and display the modified environment. If command is specified, execute it under the modified environment.

Options

• -, -i, --ignore-environment
• Ignore current environment entirely.
• -u name, --unset name
• Unset the specified variable.
• --help
• Print help message and then exit.
• --version
• Print version information and then exit.

Create a list of function and macro names that are defined in the specified C, Pascal, FORTRAN, yacc, or flex source files. The output list (named tags by default) contains lines of the form:

name file context

where name is the function or macro name, file is the source file in which name is defined, and context is a search pattern that shows the line of code containing name. After the list of tags is created, you can invoke Emacs on any file and type:

ESC-x visit-tags-table

You will be prompted for the name of the tag table; the default is TAGS. To switch to the source file associated with the name listed in tagsfile, type:

ESC-x find-tag

You will be prompted for the tag you would like Emacs to search for. ctags produces an equivalent tags file for use with vi.

Options

• -a, --append
• Append tag output to existing list of tags.
• -d, --defines
• Include tag entries for C preprocessor definitions.
• -i file, --include=file
• Add a note to the tags file that file should be consulted in addition to the normal input file.
• -l language, --language=language
• Consider the files that follow this option to be written in language. Use the -h option for a list of languages and their default filename extensions.
• -o file, --output=file
• Write to file.
• -r regexp, --regex=regexp
• Include a tag for each line that matches regexp in the files following this option.
• -C, --c++
• Expect c and h files to contain C++, not C, code.
• -D, --no-defines
• Do not include tag entries for C preprocessor definitions.
• -H, -h, --help
• Print usage information.
• -R, --noregex
• Don't include tags based on regular-expression matching for the files that follow this option.
• -S, --ignore-indentation
• Normally etags uses indentation to parse the tag file; this option tells it to rely on it less.
• -V, --version
• Print the version number.

An interactive command-based editor. For more information, see "The vi Editor".

Convert tabs in given files (or standard input, if the file is named -) to appropriate number of spaces; write results to standard output.

Options

• -tabs, -t, --tabs tabs
• tabs is a comma-separated list of integers that specify the placement of tab stops. If exactly one integer is provided, the tab stops are set to every integer spaces. By default, tab stops are 8 spaces apart. With -t and --tabs, the list may be separated by whitespace instead of commas.
• -i, --initial
• Convert tabs only at the beginning of lines.
• --help
• Print help message and then exit.
• --version
• Print version information and then exit.

Evaluate arguments as expressions and print the result. Arguments and operators must be separated by spaces. In most cases, an argument is an integer, typed literally or represented by a shell variable. There are three types of operators: arithmetic, relational, and logical, as well as keyword expressions. Exit status for expr is (expression is nonzero and nonnull), (expression is 0 or null), or (expression is invalid).

Arithmetic operators

Use these to produce mathematical expressions whose results are printed:

• +
• Add arg2 to arg1.
• -
• Subtract arg2 from arg1.
• *
• Multiply the arguments.
• /
• Divide arg1 by arg2.
• %
• Take the remainder when arg1 is divided by arg2.

Addition and subtraction are evaluated last, unless they are grouped inside parentheses. The symbols *, (, and ) have meaning to the shell, so they must be escaped (preceded by a backslash or enclosed in single quotes).

Relational operators

Use these to compare two arguments. Arguments can also be words, in which case comparisons are defined by the locale. If the comparison statement is true, the result is 1; if false, the result is 0. Symbols > and < must be escaped.

• =, ==
• Are the arguments equal?
• !=
• Are the arguments different?
• >
• Is arg1 greater than arg2?
• >=
• Is arg1 greater than or equal to arg2?
• <
• Is arg1 less than arg2?
• <=
• Is arg1 less than or equal to arg2?

Logical operators

Use these to compare two arguments. Depending on the values, the result can be arg1 (or some portion of it), arg2, or 0. Symbols | and & must be escaped.

• |
• Logical OR; if arg1 has a nonzero (and nonnull) value, the result is arg1; otherwise, the result is arg2.
• &
• Logical AND; if both arg1 and arg2 have a nonzero (and nonnull) value, the result is arg1; otherwise, the result is 0.
• :
• Like grep; arg2 is a pattern to search for in arg1. arg2 must be a regular expression. If part of the arg2 pattern is enclosed in ( \), the result is the portion of arg1 that matches; otherwise, the result is simply the number of characters that match. By default, a pattern match always applies to the beginning of the first argument (the search string implicitly begins with a ^). Start the search string with * to match other parts of the string.

Keywords

• index string character-list
• Return the first position in string that matches the first possible character in character-list. Continue through character-list until a match is found, or return 0.
• length string
• Return the length of string.
• match string regex
• Same as string : regex.
• quote token
• Treat token as a string, even if it would normally be a keyword or an operator.
• substr string start length
• Return a section of string, beginning with start, with a maximum length of length characters. Return null when given a negative or nonnumeric start or length.

Examples

Division happens first; result is 10:

expr 5 + 10 / 2

Addition happens first; result is 7 (truncated from 7.5):

expr \( 5 + 10 \) / 2

Add 1 to variable i. This is how variables are incremented in shell scripts:

i=`expr $i + 1

Print 1 (true) if variable a is the string "hello":

expr $a = hello

Print 1 (true) if b plus 5 equals 10 or more:

expr $b + 5 \>= 10

Find the 5th, 6th, and 7th letters of the word character:

expr substr character 5 3

In the examples that follow, variable p is the string "version.100". This command prints the number of characters in p:

expr $p : '.*' Result is 11

Match all characters and print them:

expr $p : '\(.*\)' Result is "version.100"

Print the number of lowercase letters at the beginning of p:

expr $p : '[a-z]*' Result is 7

Match the lowercase letters at the beginning of p:

expr $p : '\([a-z]*\)' Result is "version"

Truncate $x if it contains five or more characters; if not, just print $x. (Logical OR uses the second argument when the first one is 0 or null; i.e., when the match fails.)

expr $x : '\(.....\)' \| $x

In a shell script, rename files to their first five letters:

mv $x `expr $x : '\(.....\)' \| $x

(To avoid overwriting files with similar names, use mv -i.)

A null command that returns an unsuccessful (nonzero) exit status. Normally used in bash scripts. See also true.

Low-level format of a floppy disk. The device for a standard format is usually /dev/fd0 or /dev/fd1.

Option

• -n
• Do not verify format after completion.

System administration command. Maintain disk partitions via a menu. fdisk displays information about disk partitions, creates and deletes disk partitions, and changes the active partition. It is possible to assign a different operating system to each of the four partitions, though only one partition is active at any given time. You can also divide a physical partition into several logical partitions. The minimum recommended size for a Linux system partition is 40MB. Normally, device will be /dev/hda, /dev/hdb, /dev/sda, /dev/sdb, /dev/hdc, /dev/hdd, and so on. See also cfdisk.

Options

• -l
• List partition tables and exit.
• -spartition
• Display the size of partition, unless it is a DOS partition.

Commands

• a
• Toggle a bootable flag on current partition.
• d
• Delete current partition.
• l
• List all partition types.
• m
• Main menu.
• n
• Create a new partition; prompt for more information.
• p
• Print a list of all partitions and information about each.
• q
• Quit; do not save.
• t
• Replace the type of the current partition.
• u
• Modify the display/entry units, which must be cylinders or sectors.
• v
• Verify: check for errors; display a summary of the number of unallocated sectors.
• w
• Save changes; exit.

System administration command. Retrieve mail from mail servers and forward it to the local mail delivery system. fetchmail retrieves mail from servers that support the common mail protocols POP2, POP3, IMAP2bis, and IMAP4. Messages are delivered via SMTP through port 25 on the local host and through your system's mail delivery agent (such as sendmail), where they can be read through the user's mail client. fetchmail settings are stored in the ~/.fetchmailrc file. Parameters and servers can also be set on the command line, which will override settings in the fetchmailrc file. fetchmail is compatible with the popclient program, and users can use both without having to adjust file settings.

Options

• -a, --all
• Retrieve all messages from server, even ones that have already been seen but left on the server. The default is to only retrieve new messages.
• -A type, --auth type
• Specify the type of authentication. type may be: password, kerberos_v5, or kerberos. Authentication type is usually established by fetchmail by default, so this option isn't very useful.
• -B n, --fetchlimit n
• Set the maximum number of messages (n) accepted from a server per query.
• -b n, --batchlimit n
• Set the maximum number of messages sent to an SMTP listener per connection. When this limit is reached, the connection will be broken and reestablished. The default of 0 means no limit.
• -c, --check
• Check for mail on a single server without retrieving or deleting messages. Works with IMAP but not well with other protocols, if at all.
• -D [domain], --smtpaddress [domain]
• Specify the domain name placed in RCPT TO lines sent to SMTP. The default is the local host.
• -E header, --envelope header
• Change the header assumed to contain the mail's envelope address (usually "X-Envelope-to:") to header.
• -e n, --expunge n
• Tell an IMAP server to EXPUNGE (i.e., purge messages marked for deletion) after n deletes. A setting of 0 indicates expunging only at the end of the session. Normally, an expunge occurs after each delete.
• -F, --flush
• For POP3 and IMAP servers, remove previously retrieved messages from the server before retrieving new ones.
• -f file, --fetchmailrc file
• Specify a nondefault name for the fetchmail configuration file.
• -I specification, --interface specification
• Require that the mail server machine is up and running at a specified IP address (or range) before polling. The specification is given as interface/ipaddress/mask. The first part indicates the type of TCP connection expected (sl0, ppp0, etc.), the second is the IP address, and the third is the bit mask for the IP, assumed to be 255.255.255.255.
• -K, --nokeep
• Delete all retrieved messages from the mail server.
• -k, --keep
• Keep copies of all retrieved messages on the mail server.
• -l size, --limit size
• Set the maximum message size that will be retrieved from a server. Messages larger than this size will be left on the server and marked unread.
• -M interface, --monitor interface
• In daemon mode, monitor the specified TCP/IP interface for any activity besides itself, and skip the poll if there is no other activity. Useful for PPP connections that automatically time out with no activity.
• -m command, --mda command
• Pass mail directly to mail delivery agent, rather than send to port 25. The command is the path and options for the mailer, such as /usr/lib/sendmail -oem. A %T in the command will be replaced with the local delivery address, and an %F will be replaced with the message's From address.
• -n, --norewrite
• Do not expand local mail IDs to full addresses. This option will disable expected addressing and should only be used to find problems.
• -P n, --port n
• Specify a port to connect to on the mail server. The default port numbers for supported protocols are usually sufficient.
• -p proto, --protocol proto
• Specify the protocol to use when polling a mail server. proto can be:
  • POP2
  • Post Office Protocol 2.
  • POP3
  • Post Office Protocol 3.
  • APOP
  • POP3 with MD5 authentication.
  • RPOP
  • POP3 with RPOP authentication.
  • KPOP
  • POP3 with Kerberos v4 authentication on port 1109.
  • IMAP
  • IMAP2bis, IMAP4, or IMAP4rev1. fetchmail autodetects their capabilities.
  • IMAP-K4
  • IMAP4 or IMAP4rev1 with Kerberos v4 authentication.
  • IMAP-GSS
  • IMAP4 or IMAP4rev1 with GSSAPI authentication.
  • ETRN
  • ESMTP.
• -Q string, --qvirtual string
• Remove the prefix string, which is the local user's hostid, from the address in the envelope header (such as "Delivered-To:").
• -r folder, --folder folder
• Retrieve the specified mail folder from the mail server.
• -s, --silent
• Suppress status messages during a fetch.
• -U, --uidl
• For POP3, track the age of kept messages via unique ID listing.
• -u name, --username name
• Specify the user name to use when logging into the mail server.
• -V, --version
• Print the version information for fetchmail and display the options set for each mail server. Performs no fetch.
• -v, --verbose
• Display all status messages during a fetch.
• -Z nnn, --antispam nnn
• Specify the SMTP error nnn to signal a spam block from the client. If nnn is -1, this option is disabled.

Search one or more files for lines that match a literal text string pattern. Exit status is 0 if any lines match, 1 if not, and 2 for errors.

See grep for the list of available options. Also see egrep.

Examples

Print lines in file that don't contain any spaces:

fgrep -v '' file

Print lines in file that contain the words in spell_list:

fgrep -f spell_list file

Classify the named files according to the type of data they contain. file checks the magic file (usually /usr/share/magic) to identify some file types.

Options

• -b
• Brief mode; do not prepend filenames to output lines.
• -c
• Check the format of the magic file (files argument is invalid with -c). Usually used with -m.
• -f file
• Read the names of files to be checked from file.
• -L
• Follow symbolic links. By default, symbolic links are not followed.
• -m file
• Search for file types in file instead of /usr/share/magic.
• -n
• Flush standard output after checking a file.
• -s
• Check files that are block or character special files in addition to checking ordinary files.
• -v
• Print the version.
• -z
• Attempt checking of compressed files.

Many file types are understood. Output lists each filename, followed by a brief classification such as:

ascii text c program text c-shell commands data empty iAPX 386 executable directory [nt]roff, tbl, or eqn input text shell commands symbolic link to ../usr/etc/arp

Example

List all files that are deemed to be troff/nroff input:

file * | grep roff

An extremely useful command for finding particular groups of files (numerous examples follow this description). find descends the directory tree beginning at each pathname and locates files that meet the specified conditions. The default pathname is the current directory. The most useful conditions include -print (which is the default if no other expression is given), -name and -type (for general use), -exec and -size (for advanced users), and -mtime and -user (for administrators).

Conditions may be grouped by enclosing them in ( ) (escaped parentheses), negated with ! (use ! in the C shell), given as alternatives by separating them with -o, or repeated (adding restrictions to the match; usually only for -name, -type, -perm). Modification refers to editing of a file's contents. Change refers to modification, permission or ownership changes, and so on; therefore, for example, -ctime is more inclusive than -atime or -mtime.

Conditions and actions

• -atime +n | -n | n
• Find files that were last accessed more than n (+n), less than n (-n), or exactly n days ago. Note that find changes the access time of directories supplied as pathnames.
• -ctime +n | -n | n
• Find files that were changed more than n (+n), less than n (-n), or exactly n days ago. A change is anything that changes the directory entry for the file, such as a chmod.
• -depth
• Descend the directory tree, skipping directories and working on actual files first (and then the parent directories). Useful when files reside in unwritable directories (e.g., when using find with cpio).
• -exec command { } \;
• Run the Linux command, from the starting directory on each file matched by find (provided command executes successfully on that file; i.e., returns a 0 exit status). When command runs, the argument { } substitutes the current file. Follow the entire sequence with an escaped semicolon (;).
• -follow
• Follow symbolic links and track the directories visited (don't use this with -type l).
• -group gname
• Find files belonging to group gname. gname can be a group name or a group ID number.
• -inum n
• Find files whose inode number is n.
• -links n
• Find files having n links.
• -mount, -xdev
• Search for files that reside only on the same filesystem as pathname.
• -mtime +n | -n | n
• Find files that were last modified more than n (+n), less than n (-n), or exactly n days ago. A modification is a change to a file's data.
• -name pattern
• Find files whose names match pattern. Filename metacharacters may be used but should be escaped or quoted.
• -newer file
• Find files that have been modified more recently than file; similar to -mtime. Affected by -follow only if it occurs after -follow on the command line.
• -ok command { }\;
• Same as -exec but prompts user to respond with y before command is executed.
• -perm nnn
• Find files whose permission flags (e.g., rwx) match octal number nnn exactly (e.g., 664 matches -rw-rw-r--). Use a minus sign before nnn to make a "wildcard" match of any unspecified octal digit (e.g., -perm -600 matches -rw-******, where * can be any mode).
• -print
• Print the matching files and directories, using their full pathnames. Return true.
• -regex pattern
• Like -path but uses grep-style regular expressions instead of the shell-like globbing used in -name and -path.
• -size n[c]
• Find files containing n blocks, or if c is specified, n characters long.
• -type c
• Find files whose type is c. c can be b (block special file), c (character special file), d (directory), p (fifo or named pipe), l (symbolic link), s (socket), or f (plain file).
• -user user
• Find files belonging to user (name or ID).
• -daystart
• Calculate times from the start of the day today, not 24 hours ago.
• -maxdepth num
• Do not descend more than num levels of directories.
• -mindepth num
• Begin applying tests and actions only at levels deeper than num levels.
• -noleaf
• Normally, find assumes that each directory has at least two hard links that should be ignored (a hard link for its name and one for "."; i.e., two fewer "real" directories than its hard link count indicates). -noleaf turns off this assumption, a useful practice when find runs on non-Unix-style filesystems. This forces find to examine all entries, assuming that some might prove to be directories into which it must descend (a time-waster on Unix).
• -amin +n | -n | n
• Find files last accessed more than n (+n), less than n (-n), or exactly n minutes ago.
• -anewer file
• Find files that were accessed after file was last modified. Affected by -follow when after -follow on the command line.
• -cmin +n | -n | n
• Find files last changed more than n (+n), less than n (-n), or exactly n minutes ago.
• -cnewer file
• Find files that were changed after they were last modified. Affected by -follow when after -follow on the command line.
• -empty
• Continue if file is empty. Applies to regular files and directories.
• -false
• Return false value for each file encountered.
• -fstype type
• Match files only on type filesystems. Acceptable types include minix, ext, ext2, xia, msdos, umsdos, vfat, proc, nfs, iso9660, hpfs, sysv, smb, and ncpfs.
• -gid num
• Find files with numeric group ID of num.
• -ilname pattern
• A case-insensitive version of -lname.
• -iname pattern
• A case-insensitive version of -name.
• -ipath pattern
• A case-insensitive version of -path.
• -iregex pattern
• A case-insensitive version of -regex.
• -lname pattern
• Search for files that are symbolic links, pointing to files named pattern. pattern can include shell metacharacters and does not treat / or specially. The match is case-insensitive.
• -mmin +n | -n | n
• Find files last modified more than n (+n), less than n (-n), or exactly n minutes ago.
• -nouser
• The file's user ID does not correspond to any user.
• -nogroup
• The file's group ID does not correspond to any group.
• -path pattern
• Find files whose names match pattern. Expect full pathnames relative to the starting pathname (i.e., do not treat / or specially).

Examples

List all files (and subdirectories) in your home directory:

find $HOME -print

List all files named in the /work directory:

find /work -name chapter1 -print

List all files beginning with memo owned by ann:

find /work -name 'memo*' -user ann -print

Search the filesystem (begin at root) for manpage directories:

find / -type d -name 'man*' -print

Search the current directory, look for filenames that don't begin with a capital letter, and send them to the printer:

find . \! -name '[A-Z]*' -exec lpr {}\;

Find and compress files whose names don't end with gz:

gzip `find . \! -name '*.gz' -print

Remove all empty files on the system (prompting first):

find / -size 0 -ok rm {} \;

Search the system for files that were modified within the last two days (good candidates for backing up):

find / -mtime -2 -print

Recursively grep for a pattern down a directory tree:

find /tutorial -print | xargs grep '[Nn]utshell'

If the files kt1 and kt2 exist in the current directory, their names can be printed with the command:

$ find . -name 'kt[0-9]' ./kt1 ./kt2

Since the command prints these names with an initial ./ path, you need to specify the ./ when using the -path option:

$ find . -path './kt[0-9]' ./kt1 ./kt2

The -regex option uses a complete pathname, like -path, but treats the following argument as a regular expression rather than a glob pattern (although in this case the result is the same):

$ find . -regex './kt[0-9]' ./kt1 ./kt2

Display data about one or more users, including information listed in the files plan and project in each user's home directory. You can specify each user either as a login name (exact match) or as a first or last name (display information on all matching names). Networked environments recognize arguments of the form user@host and @host.

Options

• -l
• Force long format (default): everything included by the -s option and home directory, home phone, login shell, mail status, plan, project, and forward.
• -m
• Suppress matching of users' "real" names.
• -p
• Omit plan and project files from display.
• -s
• Show short format: login name, real name, terminal name, write status, idle time, office location, and office phone number.

TCP/IP command. Remote user information server. fingerd provides a network interface to the finger program. It listens for TCP connections on the finger port and, for each connection, reads a single input line, passes the line to finger, and copies the output of finger to the user on the client machine. fingerd is started by inetd and must have an entry in inetd's configuration file, /etc/inetd.conf.

Option

• -w
• Include additional information, such as uptime and the name of the operating system.

flex (Fast Lexical Analyzer Generator) is a faster variant of lex. It generates a lexical analysis program (named lex.yy.c) based on the regular expressions and C statements contained in one or more input files. See also bison, yacc, and the Anonymous tutorial lex & yacc by John Levine, Tony Mason, and Doug Brown.

Options

• -b
• Generate backup information to lex.backup.
• -d
• Debug mode.
• -f
• Use faster compilation (limited to small programs).
• -h
• Help summary.
• -i
• Scan case-insensitively.
• -l
• Maximum lex compatibility.
• -o file
• Write output to file instead of lex.yy.c.
• -p
• Print performance report.
• -s
• Exit if the scanner encounters input that does not match any of its rules.
• -t
• Print to standard out. (By default, flex prints to lex.yy.c.)
• -v
• Print a summary of statistics.
• -w
• Suppress warning messages.
• -B
• Generate batch (noninteractive) scanner.
• -F
• Use the fast scanner table representation.
• -I
• Generate an interactive scanner (default).
• -L
• Suppress #line directives in lex.yy.c.
• -P prefix
• Change default yy prefix to prefix for all globally visible variable and function names.
• -V
• Print version number.
• -7
• Generate a 7-bit scanner.
• -8
• Generate an 8-bit scanner (default).
• -+
• Generate a C++ scanner class.
• -C
• Compress scanner tables but do not use equivalence classes.
• -Ca
• Align tables for memory access and computation. This creates larger tables but gives faster performance.
• -Ce
• Construct equivalence classes. This creates smaller tables and sacrifices little performance (default).
• -Cf
• Generate full scanner tables, not compressed.
• -CF
• Generate faster scanner tables, like -F.
• -Cm
• Construct metaequivalence classes (default).
• -Cr
• Bypass use of the standard I/O library. Instead use read() system calls.

Convert text to specified width by filling lines and removing newlines. Concatenate files on the command line, or read text from standard input if - (or no file) is specified. By default, preserve blank lines, spacing, and indentation. fmt attempts to break lines at the end of sentences and to avoid breaking lines after a sentence's first word or before its last.

Options

• -c, --crown-margin
• Crown margin mode. Do not change each paragraph's first two lines' indentation. Use the second line's indentation as the default for subsequent lines.
• -p prefix, --prefix=prefix
• Format only lines beginning with prefix.
• -s, --split-only
• Suppress line-joining.
• -t, --tagged-paragraph
• Tagged paragraph mode. Same as crown mode when the indentation of the first and second lines differs. If the indentation is the same, treat the first line as its own separate paragraph.
• -u, --uniform-spacing
• Print exactly one space between words and two between sentences.
• -w width, --width=width
• Set output width to width. The default is 75.
• --help
• Print help message and then exit.
• --version
• Print version information and then exit.

Break the lines of the named files so that they are no wider than the specified width (default is 80). fold breaks lines exactly at the specified width, even in the middle of a word. Reads from standard input when given - as a file.

Options

• -b, --bytes
• Count bytes, not columns (i.e., consider tabs, backspaces, and carriage returns to be one column).
• -s, --spaces
• Break at spaces only, if possible.
• -w, --width width
• Set the maximum line width to width. Default is 80.

Filter standard input into mailbox format. If no sender is apparent, provide the sender foo@bar. By default, escape bogus From lines with >.

Options

• +skip
• Do not split first skip messages.
• -total
• Stop after splitting total messages.
• -a headerfield
• Append headerfield to header, unless it already exists. If headerfield is Message-ID or Resent-Message-ID with no contents, generate a unique message ID.
• -b
• Do not escape bogus From lines.
• -c
• When header fields are more than one line long, concatenate the lines.
• -d
• Do not assume that input must be in strict mailbox format.
• -e
• Allow messages to begin one immediately after the other; do not require empty space between them.
• -f
• Do not edit non-mailbox-format lines. By default, formail prepends From to such lines.
• -i headerfield
• Append headerfield whether or not it already exists. Rename each existing headerfield to Old-headerfield, unless they are empty.
• -k
• For use only with -r. Keep the body as well as the fields specified by -r.
• -m minfields
• Require at least minfields before recognizing the beginning of a new message. Default is 2.
• -n
• Allow simultaneous formail processes to run.
• -p prefix
• Escape lines with prefix instead of >.
• -q
• Do not display write errors, duplicate messages, and mismatched Content-Length fields. This is the default; use -q- to turn it off.
• -r
• Throw away all existing fields, retaining only X-Loop, and generate autoreply header instead. You can preserve particular fields with the -i option.
• -s
• Must be the last option; everything following it will be assumed to be its arguments. Divide input to separate mail messages, and pipe them to the program specified or concatenate them to standard output (by default).
• -t
• Assume sender's return address to be valid. (By default, formail favors machine-generated addresses.)
• -u headerfield
• Delete all but the first occurrence of headerfield.
• -x headerfield
• Display the contents of headerfield on a single line.
• -z
• When necessary, add a space between field names and contents. Remove ("zap") empty fields.
• -A headerfield
• Append headerfield whether or not it already exists.
• -B
• Assume that input is in BABYL rmail format.
• -D maxlen idcache
• Remember old message IDs (in idcache, which will grow no larger than approximately maxlen). When splitting, refuse to output duplicate messages. Otherwise, return true on discovering a duplicate. With -r, look at the sender's mail address instead of the message ID.
• -I headerfield
• Append headerfield whether or not it already exists. Remove existing fields.
• -R oldfield newfield
• Change all fields named oldfield to newfield.
• -U headerfield
• Delete all but the last occurrence of headerfield.
• -Y
• Format in traditional Berkeley style (i.e., ignore Content-Length fields).
• -X headerfield
• Display the field name and contents of headerfield on a single line.

Display statistics about memory usage: total free, used, physical, swap, shared, and buffers used by the kernel.

Options

• -b
• Calculate memory in bytes.
• -k
• Default. Calculate memory in kilobytes.
• -m
• Calculate memory in megabytes.
• -o
• Do not display "buffer adjusted" line. The -o switch disables the display "-/+ buffers" line.
• -s time
• Check memory usage every time seconds.
• -t
• Display all totals on one line at the bottom of output.
• -V
• Display version information.

System administration command. Call the filesystem checker for the appropriate system type, to check and repair filesystems. If a filesystem is consistent, the number of files, number of blocks used, and number of blocks free are reported. If a filesystem is inconsistent, fsck prompts before each correction is attempted. fsck's exit code can be interpreted as the sum of all of those conditions that apply:

• Errors were found and corrected.
• Reboot suggested.
• Errors were found but not corrected.
• fsck encountered an operational error.
• fsck was called incorrectly.
• A shared library error was detected.

Options

• --
• Pass all subsequent options to filesystem-specific checker. All options that fsck doesn't recognize will also be passed.
• -r
• Interactive mode; prompt before making any repairs.
• -s
• Serial mode.
• -t fstype
• Specify the filesystem type. Do not check filesystems of any other type.
• -A
• Check all filesystems listed in /etc/fstab.
• -N
• Suppress normal execution; just display what would be done.
• -R
• Meaningful only with -A: check all filesystems listed in /etc/fstab except the root filesystem.
• -T
• Suppress printing of title.
• -V
• Verbose mode.

System administration command. Similar to fsck, but specifically intended for Linux MINIX filesystems.

Options

• -a
• Automatic mode; repair without prompting.
• -f
• Force checking, even if kernel has already marked the filesystem. fsck.minix will normally exit without checking if the system appears to be clean.
• -l
• List filesystems.
• -m
• Enable MINIX-like "mode not cleared" warnings.
• -r
• Interactive mode; prompt before making any repairs.
• -s
• Display information about superblocks.
• -v
• Verbose mode.

Transfer files to and from remote network site hostname. ftp prompts the user for a command. The commands are listed after the options. Some of the commands are toggles, meaning they turn on a feature when it is off and vice versa.

Options

• -d
• Enable debugging.
• -g
• Disable filename globbing.
• -i
• Turn off interactive prompting.
• -n
• No autologin upon initial connection.
• -v
• Verbose. Show all responses from remote server.

Commands

• ![command [args]]
• Invoke an interactive shell on the local machine. If arguments are given, the first is taken as a command to execute directly, with the rest of the arguments as that command's arguments.
• $ macro-name [args]
• Execute the macro macro-name that was defined with the macdef command. Arguments are passed to the macro unglobbed.
• account [passwd]
• Supply a supplemental password that will be required by a remote system for access to resources once a login has been successfully completed. If no argument is given, the user will be prompted for an account password in a nonechoing mode.
• append local-file [remote-file]
• Append a local file to a file on the remote machine. If remote-file is not given, the local filename is used after being altered by any ntrans or nmap setting. File transfer uses the current settings for type, format, mode, and structure.
• ascii
• Set the file transfer type to network ASCII (default).
• bell
• Sound a bell after each file transfer command is completed.
• binary
• Set file transfer type to support binary image transfer.
• bye
• Terminate FTP session and then exit ftp.
• case
• Toggle remote computer filename case mapping during mget. The default is off. When case is on, files on the remote machine with all-uppercase names will be copied to the local machine with all-lowercase names.
• cd remote-directory
• Change working directory on remote machine to remote-directory.
• cdup
• Change working directory of remote machine to its parent directory.
• chmod [mode] [remote-file]
• Change file permissions of remote-file. If options are omitted, the command prompts for them.
• close
• Terminate FTP session and return to command interpreter.
• cr
• Toggle carriage return stripping during ASCII-type file retrieval.
• delete remote-file
• Delete file remote-file on remote machine.
• debug [debug-value]
• Toggle debugging mode. If debug-value is specified, it is used to set the debugging level.
• dir [remote-directory] [local-file]
• Print a listing of the contents in the directory remote-directory, and, optionally, place the output in local-file. If no directory is specified, the current working directory on the remote machine is used. If no local file is specified or - is given instead of the filename, output comes to the terminal.
• disconnect
• Synonym for close.
• form format
• Set the file transfer form to format. Default format is file.
• get remote-file [local-file]
• Retrieve the remote-file and store it on the local machine. If the local filename is not specified, it is given the same name it has on the remote machine, subject to alteration by the current case, ntrans, and nmap settings. If local file is -, output comes to the terminal.
• glob
• Toggle filename expansion for mdelete, mget, and mput. If globbing is turned off, the filename arguments are taken literally and not expanded.
• hash
• Toggle hash-sign (#) printing for each data block transferred.
• help [command]
• Print help information for command. With no argument, ftp prints a list of commands.
• idle [seconds]
• Get/set idle timer on remote machine. seconds specifies the length of the idle timer; if omitted, the current idle timer is displayed.
• image
• Same as binary.
• lcd [directory]
• Change working directory on local machine. If directory is not specified, the user's home directory is used.
• ls [remote-directory] [local-file]
• Print listing of contents of directory on remote machine, in a format chosen by the remote machine. If remote-directory is not specified, current working directory is used.
• macdef macro-name
• Define a macro. Subsequent lines are stored as the macro macro-name; a null line terminates macro input mode. When $i is included in the macro, loop through arguments, substituting the current argument for $i on each pass. Escape $ with .
• mdelete remote-files
• Delete the remote-files on the remote machine.
• mdir remote-files local-file
• Like dir, except multiple remote files may be specified.
• mget remote-files
• Expand the wildcard expression remote-files on the remote machine and do a get for each filename thus produced.
• mkdir directory-name
• Make a directory on the remote machine.
• mls remote-files local-file
• Like nlist, except multiple remote files may be specified, and the local file must be specified.
• mode [mode-name]
• Set file transfer mode to mode-name. Default mode is stream mode.
• modtime [file-name]
• Show last modification time of the file on the remote machine.
• mput [local-files]
• Expand wildcards in local-files given as arguments and do a put for each file in the resulting list.
• newer remote-file [local-file]
• Get file if remote file is newer than local file.
• nlist [remote-directory] [local-file]
• Print list of files of a directory on the remote machine to local-file (or the screen if local-file is not specified). If remote-directory is unspecified, the current working directory is used.
• nmap [inpattern outpattern]
• Set or unset the filename mapping mechanism. The mapping follows the pattern set by inpattern, a template for incoming filenames, and outpattern, which determines the resulting mapped filename. The sequences $1 through $9 are treated as variables, for example, the inpattern $1.$2, along with the input file readme.txt, would set $1 to readme and $2 to txt. An outpattern of $1.data would result in an output file of readme.data. $0 corresponds to the complete filename. [string1, string2] is replaced by string1, unless that string is null, in which case it's replaced by string2.
• ntrans [inchars [outchars ]]
• Set or unset the filename character translation mechanism. Characters in a filename matching a character in inchars are replaced with the corresponding character in outchars. If no arguments are specified, the filename mapping mechanism is unset. If arguments are specified:
  • Characters in remote filenames are translated during mput and put commands issued without a specified remote target filename.
  • Characters in local filenames are translated during mget and get commands issued without a specified local target filename.
• open host [port]
• Establish a connection to the specified host FTP server. An optional port number may be supplied, in which case ftp will attempt to contact an FTP server at that port.
• prompt
• Toggle interactive prompting.
• proxy ftp-command
• Execute an FTP command on a secondary control connection (i.e., send commands to two separate remote hosts simultaneously).
• put local-file [remote-file]
• Store a local file on the remote machine. If remote-file is left unspecified, the local filename is used after processing according to any ntrans or nmap settings in naming the remote file. File transfer uses the current settings for type, file, structure, and transfer mode.
• pwd
• Print name of the current working directory on the remote machine.
• quit
• Synonym for bye.
• quote arg1 arg2...
• Send the arguments specified, verbatim, to the remote FTP server.
• recv remote-file [local-file]
• Synonym for get.
• reget remote-file [local-file]
• Retrieve a file (like get), but restart at the end of local-file. Useful for restarting a dropped transfer.
• remotehelp [command-name]
• Request help from the remote FTP server. If command-name is specified, remote help for that command is returned.
• remotestatus [filename]
• Show status of the remote machine, or, if filename is specified, filename on remote machine.
• rename [from] [to]
• Rename file from on remote machine to to.
• reset
• Clear reply queue.
• restart marker
• Restart the transfer of a file from a particular byte count.
• rmdir [directory-name]
• Delete a directory on the remote machine.
• runique
• Toggle storing of files on the local system with unique filenames. When this option is on, rename files as or , and soon, as appropriate, to preserve unique filenames, and report each such action. Default value is off.
• send local-file [remote-file]
• Synonym for put.
• sendport
• Toggle the use of PORT commands.
• site [command]
• Get/set site-specific information from/on remote machine.
• size filename
• Return size of filename on remote machine.
• status
• Show current status of ftp.
• struct [struct-name]
• Set the file transfer structure to struct-name. By default, stream structure is used.
• sunique
• Toggle storing of files on remote machine under unique filenames.
• system
• Show type of operating system running on remote machine.
• tenex
• Set file transfer type to that needed to talk to TENEX machines.
• trace
• Toggle packet tracing.
• type [type-name]
• Set file transfer type to type-name. If no type is specified, the current type is printed. The default type is network ASCII.
• umask [mask]
• Set user file-creation mode mask on the remote site. If mask is omitted, the current value of the mask is printed.
• user username [password] [account]
• Identify yourself to the remote FTP server. ftp will prompt the user for the password, if not specified and the server requires it, and the account field.
• verbose
• Toggle verbose mode.
• ? [command]
• Same as help.

TCP/IP command. Internet File Transfer Protocol server. The server uses the TCP protocol and listens at the port specified in the ftp service specification. ftpd is started by inetd and must have an entry in inetd's configuration file, /etc/inetd.conf.

Options

• -d
• Write debugging information to the syslog.
• -l
• Log each FTP session in the syslog.
• -Tmaxtimeout
• Set maximum timeout period in seconds. Default limit is 15 minutes.
• -ttimeout
• Set timeout period to timeout seconds.

Identify processes that are using a file or filesystem. fuser outputs the process IDs of the processes that are using the files or local filesystems. Each process ID is followed by a letter code: c if process is using file as current directory, e if executable, f if an open file, m if a shared library, and r if the root directory. Any user with permission to read /dev/kmem and /dev/mem can use fuser, but only a privileged user can terminate another user's process. fuser does not work on remote (NFS) files.

If more than one group of files is specified, the options may be respecified for each additional group of files. A lone dash (-) cancels the options currently in force, and the new set of options applies to the next group of files.

Options

• -
• Return all options to defaults.
• -signal
• Send signal instead of SIGKILL.
• -a
• Display information on all specified files, even if they are not being accessed by any processes.
• -i
• Request user confirmation to kill a process. Ignored if -k is not also specified.
• -k
• Send SIGKILL signal to each process.
• -l
• List signal names.
• -m
• Expect files to exist on a mounted filesystem; include all files accessing that filesystem.
• -s
• Silent.
• -u
• User login name, in parentheses, also follows process ID.
• -v
• Verbose.
• -V
• Display version information.

Invoke gcc with the options necessary to make it recognize C++. g++ recognizes all the file extensions gcc does, in addition to C++ source files (C, cc, or cxx files) and C++ preprocessed files (ii files). See also gcc.

TCP/IP command. Gateway routing daemon. gated handles multiple routing protocols and replaces routed and any routing daemons that speak the Hello, EGP, or BGP routing protocols. gated currently handles the RIP, BGP, EGP, Hello, and OSPF routing protocols and can be configured to perform all or any combination of the five.

Options

• -c
• Parse configuration file for syntax errors, then exit gated, leaving a dump file in /usr/tmp/gated_dump.
• -f config_file
• Use alternate configuration file, config_file. Default is /etc/gated.conf.
• -n
• Do not modify kernel's routing table.
• -t [trace_options]
• Start gated with the specified tracing options enabled. If no flags are specified, assume general. The trace flags are:
  • adv
  • Management of policy blocks.
  • all
  • Includes normal, policy, route, state, task, and timer.
  • general
  • Includes normal and route.
  • iflist
  • The kernel interface list.
  • normal
  • Normal protocols instances.
  • parse
  • Lexical analyzer and parser.
  • policy
  • Instances in which policy is applied to imported and exported routes.
  • route
  • Any changes to routing table.
  • state
  • State machine transitions.
  • symbols
  • Symbols read from kernel -- note that they are read before the configuration file is parsed, so this option must be specified on the command line.
  • task
  • System tasks and interfaces.
  • timer
  • Timer usage.
• -C
• Parse configuration file for errors and set exit code to indicate if there were any (1) or not (0), then exit.
• -N
• Do not daemonize.

gawk [options] -f scriptfile [var=value...] [files]

The GNU version of awk, a program that does pattern matching, record processing, and other forms of text manipulation. For more information, see "The gawk Scripting Language".

Compile one or more C source files (file.c), assembler source files (file.s), or preprocessed C source files (file.i). If the file suffix is not recognizable, assume that the file is an object file or library. gcc automatically invokes the link editor ld (unless -c, -S, or -E is supplied). In some cases, gcc generates an object file having a o suffix and a corresponding root name. By default, output is placed in a.out. gcc accepts many system-specific options not covered here.

Note: gcc is the GNU form of cc; on most Linux systems, the command cc will invoke gcc. The command g++ will invoke gcc with the appropriate options for interpreting C++.

Options

• -a
• Provide profile information for basic blocks.
• -ansi
• Enforce full ANSI conformance.
• -b machine
• Compile for use on machine type.
• -c
• Create linkable object file for each source file, but do not call linker.
• -dD
• Print #defines.
• -dM
• Suppress normal output. Print series of #defines that are in effect at the end of preprocessing.
• -dN
• Print #defines with macro names only, not arguments or values.
• -fno-asm
• Do not recognize asm, inline, or typeof as keywords. Implied by -ansi.
• -fno-builtin
• Do not recognize built-in functions unless they begin with two underscores.
• -fno-gnu-keywords
• Do not recognize classof, headof, signature, sigof, or typeof as keywords.
• -fno-ident
• Do not respond to #ident commands.
• -fsigned-bitfields
• -funsigned-bitfields
• -fno-signed-bitfields
• -fno-unsigned-bitfields
• Set default control of bitfields to signed or unsigned if not explicitly declared.
• -fsigned-char
• Cause the type char to be signed.
• -fsyntax-only
• Check for syntax errors. Do not attempt to actually compile.
• -funsigned-char
• Cause the type char to be unsigned.
• -g
• Include debugging information for use with gdb.
• -glevel
• Provide level amount of debugging information. level must be 1, 2, or 3, with 1 providing the least amount of information. The default is 2.
• -idirafter dir
• Include dir in the list of directories to search when an include file is not found in the normal include path.
• -include file
• Process file before proceeding to the normal input file.
• -imacros file
• Process the macros in file before proceeding to the normal input file.
• -iprefix prefix
• When adding directories with -iwithprefix, prepend prefix to the directory's name.
• -isystem dir
• Add dir to the list of directories to be searched when a system file cannot be found in the main include path.
• -iwithprefix dir
• Append dir to the list of directories to be searched when a header file cannot be found in the main include path. If -iprefix has been set, prepend that prefix to the directory's name.
• -llib
• Link to lib.
• -nostartfiles
• Force linker to ignore standard system startup files.
• -nostdinc
• Search only specified, not standard, directories for header files.
• -nostdinc++
• Suppress searching of directories believed to contain C++-specific header files.
• -nostdlib
• Suppress linking to standard library files.
• -o file
• Specify output file as file. Default is a.out.
• -p
• Provide profile information for use with prof.
• -pedantic
• Warn verbosely.
• -pedantic-errors
• Err in every case in which -pedantic would have produced a warning.
• -pg
• Provide profile information for use with gprof.
• -pipe
• Transfer information between stages of compiler by pipes instead of temporary files.
• -s
• Remove all symbol table and relocation information from the executable.
• -save-temps
• Save temporary files in the current directory when compiling.
• -static
• Suppress linking to shared libraries.
• -traditional
• Attempt to behave like a traditional C compiler.
• -traditional-cpp
• Cause the preprocessor to attempt to behave like a traditional C preprocessor.
• -trigraphs
• Include trigraph support.
• -u symbol
• Force the linker to search libraries for a definition of symbol and to link to them, if found.
• -undef
• Define only those constants required by the language standard, not system-specific constants like unix.
• -v
• Verbose mode. Display commands as they are executed, gcc version number, and preprocessor version number.
• -w
• Suppress warnings.
• -x language
• Expect input file to be written in language, which may be c, objective-c, c-header, c++, cpp-output, assembler, or assembler-with-cpp. If none is specified as language, guess the language by filename extension.
• -Aquestion(answer)
• If the preprocessor encounters a conditional such as #if question, assert answer in response. To turn off standard assertions, use -A-.
• -Bpath
• Specify the path directory in which the compiler files are located.
• -C
• Retain comments during preprocessing. Meaningful only with -E.
• -Dname[=def]
• Define name with value def as if by a #define. If no =def is given, name is defined with value 1. -D has lower precedence than -U.
• -E
• Preprocess the source files, but do not compile. Print result to standard output.
• -Idir
• Include dir in list of directories to search for include files. If dir is -, search those directories that were specified by -I before the -I- only when #include "file" is specified, not #include <file>.
• -Ldir
• Search dir in addition to standard directories.
• -M
• Instead of compiling, print a rule suitable for inclusion in a makefile that describes dependencies of the source file based on its #include directives. Implies -E.
• -MD
• Similar to -M, but sends dependency information to files ending in d in addition to ordinary compilation.
• -MG
• Used with -M or -MM. Suppress error messages if an included file does not exist; useful if the included file is automatically generated by a build.
• -MMD
• Similar to -MD, but record only user header file information, not system header file information.
• -MM
• Similar to -M, but limit the rule to non-standard #include files; that is, only files declared through #include "file" and not those declared through #include <file>.
• -H
• Print pathnames of included files, one per line, on standard error.
• -O[level]
• Optimize. level should be 1, 2, 3, or 0. The default is 1. 0 turns off optimization; 3 optimizes the most.
• -P
• Preprocess input without producing line-control information used by next pass of C compiler. Meaningful only with -E.
• -S
• Compile source files into assembler code, but do not assemble.
• -Uname
• Remove any initial definition of name, where name is a reserved symbol predefined by the preprocessor or a name defined on a -D option. Names predefined by cpp are unix and i386.
• -V version
• Attempt to run gcc version version.
• -W
• Warn more verbosely than normal.
• -Wl,option
• Invoke linker with option, which may be a comma-separated list.
• -Wa,option
• Call assembler with option, which may be a comma-separated list.
• -Waggregate-return
• Warn if any functions return structures or unions are defined or called.
• -Wall
• Enable -W, -Wchar-subscripts, -Wcomment, -Wformat, -Wimplicit, -Wparentheses, -Wreturn-type, -Wswitch, -Wtemplate-debugging, -Wtrigraphs, -Wuninitialized, and -Wunused.
• -Wcast-align
• Warn when encountering instances in which pointers are cast to types that increase the required alignment of the target from its original definition.
• -Wcast-qual
• Warn when encountering instances in which pointers are cast to types that lack the type qualifier with which the pointer was originally defined.
• -Wchar-subscripts
• Warn when encountering arrays with subscripts of type char.
• -Wcomment
• Warn when encountering the beginning of a nested comment.
• -Wconversion
• Warn in particular cases of type conversions.
• -Werror
• Exit at the first error.
• -Wformat
• Warn about inappropriately formatted printfs and scanfs.
• -Wimplicit
• Warn when encountering implicit function or parameter declarations.
• -Winline
• Warn about illegal inline functions.
• -Wmissing-declarations
• Warn if a global function is defined without a previous declaration.
• -Wmissing-prototypes
• Warn when encountering global function definitions without previous prototype declarations.
• -Wnested-externs
• Warn if an extern declaration is encountered within a function.
• -Wno-import
• Don't warn about use of #import.
• -Wp,options
• Pass options to the preprocessor. Multiple options are separated by commas. Not a warning parameter.
• -Wparentheses
• Enable more verbose warnings about omitted parentheses.
• -Wpointer-arith
• Warn when encountering code that attempts to determine the size of a function or void.
• -Wredundant-decls
• Warn if anything is declared more than once in the same scope.
• -Wreturn-type
• Warn about functions defined without return types or with improper return types.
• -Wshadow
• Warn when a local variable shadows another local variable.
• -Wstrict-prototypes
• Insist that argument types be specified in function declarations and definitions.
• -Wswitch
• Warn about switches that skip the index for one of their enumerated types.
• -Wtemplate-debugging
• Warn if debugging is not available for C++ templates.
• -Wtraditional
• Warn when encountering code that produces different results in ANSI C and traditional C.
• -Wtrigraphs
• Warn when encountering trigraphs.
• -Wuninitialized
• Warn when encountering uninitialized automatic variables.
• -Wunused
• Warn about unused variables and functions.
• -Xlinker option
• Pass an option to the linker. A linker option with an argument requires two -Xs, the first specifying the option and the second specifying the argument.

Pragma directives

• #pragma interface [header-file]
• Used in header files to force object files to provide definition information via references, instead of including it locally in each file. C++-specific.
• #pragma implementation [header-file]
• Used in main input files to force generation of full output from header-file (or, if it is not specified, from the header file with the same base name as the file containing the pragma directive). This information will be globally visible. Normally the specified header file contains a #pragma interface directive.

GDB (GNU DeBugger) allows you to step through C, C++, and Modula-2 programs in order to find the point at which they break. The program to be debugged is normally specified on the command line; you can also specify a core or, if you want to investigate a running program, a process ID.

Options

• -s file, -symbols=file
• Consult file for symbol table. With -e, also uses file as the executable.
• -e file, -exec=file
• Use file as executable, to be read in conjunction with source code. May be used in conjunction with -s to read symbol table from the executable.
• -c file, -core=file
• Consult file for information provided by a core dump.
• -x file, -command=file
• Read gdb commands from file.
• -d directory, -directory=directory
• Include directory in path that is searched for source files.
• -n, -nx
• Ignore gdbinit file.
• -q, -quiet
• Suppress introductory and copyleft messages.
• -batch
• Exit after executing all the commands specified in gdbinit and -x files. Print no startup messages.
• -cd=directory
• Use directory as gdb's working directory.
• -f, -fullname
• Show full filename and line number for each stack frame.
• -b bps
• Set line speed of serial device used by GDB to bps.
• -tty=device
• Set standard in and standard out to device.

Common commands

These are just some of the more common gdb commands; there are too many commands to list all of them here:

• bt
• Print the current location within the program and a stack trace showing how the current location was reached. (where does the same thing.)
• break
• Set a breakpoint in the program.
• cd
• Change the current working directory.
• clear
• Delete the breakpoint where you just stopped.
• commands
• List commands to be executed when breakpoint is hit.
• c
• Continue execution from a breakpoint.
• delete
• Delete a breakpoint or a watchpoint; also used in conjunction with other commands.
• display
• Cause variables or expressions to be displayed when program stops.
• down
• Move down one stack frame to make another function the current one.
• frame
• Select a frame for the next continue command.
• info
• Show a variety of information about the program. For instance, info breakpoints shows all outstanding breakpoints and watchpoints.
• jump
• Start execution at another point in the source file.
• kill
• Abort the process running under gdb's control.
• list
• List the contents of the source file corresponding to the program being executed.
• next
• Execute the next source line, executing a function in its entirety.
• print
• Print the value of a variable or expression.
• pwd
• Show the current working directory.
• ptype
• Show the contents of a datatype, such as a structure or C++ class.
• quit
• Exit gdb.
• reverse-search
• Search backward for a regular expression in the source file.
• run
• Execute the program.
• search
• Search for a regular expression in the source file.
• set variable
• Assign a value to a variable.
• signal
• Send a signal to the running process.
• step
• Execute the next source line, stepping into a function if necessary.
• undisplay
• Reverse the effect of the display command; keep expressions from being displayed.
• until
• Finish the current loop.
• up
• Move up one stack frame to make another function the current one.
• watch
• Set a watchpoint (i.e., a data breakpoint) in the program.
• whatis
• Print the type of a variable or function.

TCP/IP command. Administer gated. Various commands start and stop the daemon, send signals to it, maintain the configuration files, and manage state and core dumps.

Options

• -c size
• Specify maximum core dump size.
• -f size
• Specify maximum file dump size.
• -m size
• Specify maximum data segment size.
• -n
• Suppress editing of the kernel forwarding table.
• -q
• Quiet mode: suppress warnings and log errors to syslogd instead of standard error.
• -s size
• Specify maximum stack size.
• -t seconds
• Wait seconds seconds (default is 10) for gated to complete specified operations at start and stop time.

Commands

• BACKOUT
• Restore /etc/gated.conf from /etc/gated.conf-, whether or not the latter exists.
• backout
• Restore /etc/gated.conf from /etc/gated.conf-, assuming the latter exists.
• checkconf
• Report any syntax errors in /etc/gated.conf.
• checknew
• Report any syntax errors in /etc/gated.conf+.
• COREDUMP
• Force gated to core dump and exit.
• createconf
• Create an empty /etc/gated.conf+ if one does not already exist, and set it to mode 664, owner root, group gdmaint.
• dump
• Force gated to dump to /usr/tmp/gated_dump and then continue normal operation.
• interface
• Reload interface configuration.
• KILL
• Terminate immediately (ungracefully).
• modeconf
• Set all configuration files to mode 664, owner root, group gdmaint.
• newconf
• Make sure that /etc/gated.conf+ exists and move it to /etc/gated.conf. Save the old /etc/gated.conf as /etc/gated.conf-.
• reconfig
• Reload configuration file.
• restart
• Stop and restart gated.
• rmcore
• Remove any gated core files.
• rmdmp
• Remove any gated state dump files.
• rmparse
• Remove any gated files that report on parse errors. These are generated by the checkconf and checknew commands.
• running
• Exit with zero status if gated is running and nonzero if it is not.
• start
• Start gated, unless it is already running, in which case return an error.
• stop
• Stop gated as gracefully as possible.
• term
• Terminate gracefully.
• toggletrace
• Toggle tracing.

Files

• /etc/gcd.conf+
• The test configuration file. Once you're satisfied that it works, you should run gated newconf to install it as /etc/gated.conf.
• /etc/gated.conf-
• A backup of the old configuration file.
• /etc/gated.conf--
• A backup of the backup of the old configuration file.
• /etc/gated.conf
• The actual configuration file.
• /etc/gated.pid
• gated's process ID.
• /usr/tmp/gated_dump
• The state dump file.
• /usr/tmp/gated_parse
• A list of the parse errors generated by reading the configuration file.

Print the kernel's scancode-to-keycode mapping table.

System administration command. Set terminal type, modes, speed, and line discipline. Linux systems may use agetty instead, which uses a different syntax. getty is invoked by init. It is the second process in the series init-getty-login-shell, which ultimately connects a user with the Linux system. getty reads the user's login name and invokes the login command with the user's name as an argument. While reading the name, getty attempts to adapt the system to the speed and type of device being used.

You must specify a port argument, which getty will use to attach itself to the device /dev/port. getty will then scan the defaults file, usually /etc/default/getty, for runtime values and parameters. These may also be specified, for the most part, on the command line, but the values in the defaults file take precedence. The speed argument is used to point to an entry in the file /etc/gettydefs, which contains the initial baud rate, tty settings, and login prompt and final speed and settings for the connection. The first entry is the default in /etc/gettydefs. term specifies the type of terminal, with lined the optional line discipline to use.

Options

• -c file
• Check the gettydefs file. file is the name of the gettydefs file. Produces the files' values and reports parsing errors to standard output.
• -d file
• Use a different default file.
• -h
• Do not force a hangup on the port when initializing.
• -r delay
• Wait for single character from port, then wait delay seconds before proceeding.
• -t timeout
• If no username is accepted within timeout seconds, close connection.
• -w string
• Wait for string characters from port before proceeding.

Display the profile data for an object file. The file's symbol table is compared with the call graph profile file gmon.out (previously created by compiling with gcc -pg).

Options

• -a
• Do not display statically declared functions. Since their information might still be relevant, append it to the information about the functions loaded immediately before.
• -b
• Do not display information about each field in the profile.
• -c
• Consult the object file's text area to attempt to determine the program's static call graph. Display static-only parents and children with call counts of 0.
• -e routine
• Do not display entries for routine and its descendants.
• -f routine
• Print only routine, but include time spent in all routines.
• -k from to
• Remove arcs between the routines from and to.
• -s
• Summarize profile information in the file gmon.sum.
• -v
• Print version and exit.
• -z
• Include zero-usage calls.
• -E routine
• Do not display entries for routine and its descendants or include time spent on them in calculations for total time.
• -F routine
• Print only information about routine. Do not include time spent in other routines.

Search one or more files for lines that match a regular expression pattern. Regular expressions are described in "Pattern Matching". Exit status is 0 if any lines match, 1 if none match, and 2 for errors. See also egrep and fgrep.

Options

• -a, --text
• Don't suppress output lines with binary data; treat as text.
• -b, --byte-offset
• Print the byte offset within the input file before each line of output.
• -b, --byte-offset
• Print the byte offset within the input file before each line of output.
• -c, --count
• Print only a count of matched lines. With -v or --revert-match option, count nonmatching lines.
• -d action, --directories=action
• Define an action for processing directories. Possible actions are:
  • read
  • Read directories like ordinary files (default).
  • skip
  • Skip directories.
  • recurse
  • Recursively read all files under each directory. Same as -r.
• -e pattern, --regexp=pattern
• Search for pattern. Same as specifying a pattern as an argument, but useful in protecting patterns beginning with -.
• -f file, --file=file
• Take a list of patterns from file, one per line.
• -h, --no-filename
• Print matched lines but not filenames (inverse of -l).
• -i, --ignore-case
• Ignore uppercase and lowercase distinctions.
• -l, --files-with-matches
• List the names of files with matches but not individual matched lines; scanning per file stops on the first match.
• -n, --line-number
• Print lines and their line numbers.
• -q, --quiet, --silent
• Suppress normal output in favor of quiet mode; the scanning stops on the first match.
• -r, --recursive
• Recursively read all files under each directory. Same as -d recurse.
• -s, --no-messages
• Suppress error messages about nonexistent or unreadable files.
• -v, --revert-match
• Print all lines that don't match pattern.
• -w, --word-regexp
• Match on whole words only. Words are divided by characters that are not letters, digits, or underscores.
• -x, --line-regexp
• Print lines only if pattern matches the entire line.
• -A num, --after-context=num
• Print num lines of text that occur after the matching line.
• -B num, --before-context=num
• Print num lines of text that occur before the matching line.
• -C[num], --context=[num], -num
• Print num lines of leading and trailing context. Default context is 2 lines.
• -L, --files-without-match
• List files that contain no matching lines.
• -V, --version
• Print the version number and then exit.

Examples

List the number of users who use tcsh:

grep -c /bin/tcsh /etc/passwd

List header files that have at least one #include directive:

grep -l '^#include' /usr/include/*

List files that don't contain pattern:

grep -c pattern files | grep :0

troff [options] [files]

Frontend to the groff document-formatting system, which normally runs troff along with a postprocessor appropriate for the selected output device. Options without arguments can be grouped after a single dash (-). A filename of - denotes standard input.

Options

• -a
• Generate an ASCII approximation of the typeset output.
• -b
• Print a backtrace.
• -C
• Enable compatibility mode.
• -dcs, -dname=s
• Define the character c or string name to be the string s.
• -e
• Preprocess with eqn.
• -E
• Don't print any error messages.
• -ffam
• Use fam as the default font family.
• -Fdir
• Search dir for subdirectories with DESC and font files before the default /usr/lib/groff/font.
• -h
• Print a help message.
• -i
• Read standard input after all files have been processed.
• -l
• Send the output to a printer (as specified by the print command in the device description file).
• -Larg
• Pass arg to the spooler. Each argument should be passed with a separate -L option.
• -mname
• Read the macro file tmac.name.
• -Mdir
• Search directory dir for macro files before the default directory /usr/lib/groff/tmac.
• -nnum
• Set the first page number to num.
• -N
• Don't allow newlines with eqn delimiters; equivalent to eqn's -N option.
• -olist
• Output only pages specified in list, which is a comma-separated list of page ranges.
• -p
• Preprocess with pic.
• -Parg
• Pass arg to the postprocessor. Each argument should be passed with a separate -P option.
• -rcn, -name=n
• Set the number register c or name to n. c is a single character and n is any troff numeric expression.
• -R
• Preprocess with refer.
• -s
• Preprocess with soelim.
• -S
• Use safer mode (i.e., pass the -S option to pic and use the -msafer macros with troff).
• -t
• Preprocess with tbl.
• -Tdev
• Prepare output for device dev; the default is ps.
• -v
• Make programs run by groff print out their version number.
• -V
• Print the pipeline on stdout instead of executing it.
• -wname
• Enable warning name. You can specify multiple -w options. See the troff manpage for a list of warnings.
• -Wname
• Disable warning name. You can specify multiple -W options. See the troff manpage for a list of warnings.
• -z
• Suppress troff output (except error messages).
• -Z
• Do not postprocess troff output. Normally groff automatically runs the appropriate postprocessor.

Devices

• ascii
• Typewriter-like device
• dvi
• TeX dvi format
• latin1
• Typewriter-like devices using the ISO Latin-1 character set
• ps
• PostScript
• 75-dpi X11 previewer
• 100-dpi X11 previewer
• lj4
• HP LaserJet4-compatible (or other PCL5-compatible) printer

Environment variables

• GROFF_COMMAND_PREFIX
• If set to be X, groff will run Xtroff instead of troff.
• GROFF_FONT_PATH
• Colon-separated list of directories in which to search for the devname directory.
• GROFF_TMAC_PATH
• Colon-separated list of directories in which to search for the macro files.
• GROFF_TMPDIR
• If set, temporary files will be created in this directory; otherwise, they will be created in TMPDIR (if set) or /tmp (if TMPDIR is not set).
• GROFF_TYPESETTER
• Default device.
• PATH
• Search path for commands that groff executes.

System administration command. Create new group account group.

Options

• -ggid
• Assign numerical group ID. (By default, the first available number above 500 is used.) The value must be unique unless the -o option is used.
• -o
• Accept a nonunique gid with the -g option.

System administration command. Remove group from system account files. You may still need to find and change permissions on files that belong to the removed group.

System administration command. Modify group information for group.

Options

• -g gid
• Change the numerical value of the group ID. Any files that have the old gid will have to be changed manually. The new gid must be unique unless the -o option is used.
• -n name
• Change the group name to name.
• -o
• Override. Accept a nonunique gid.

Show the groups that each user belongs to (default user is the owner of the current group). Groups are listed in /etc/passwd and /etc/group.

Options

• --help
• Print help message.
• --version
• Print version information.

System administration command. Remove corrupt or duplicate entries in the /etc/group and /etc/gshadow files. Generate warnings for other errors found. grpck will prompt for a "yes" or "no" before deleting entries. If the user replies "no," the program will exit. If run in a noninteractive mode, the reply to all prompts is "no." Alternate group and gshadow files can be checked. If other errors are found, the user will be encouraged to run the groupmod command.

Option

• -n
• Noninteractive mode.

Exit codes

• Success.
• Syntax error.
• One or more bad group entries found.
• Could not open group files.
• Could not lock group files.
• Could not write group files.

grpunconv

System administration command. Like pwconv, the grpconv command creates a shadowed group file to keep your encrypted group passwords safe from password cracking programs. grpconv creates the /etc/gshadow file based on your existing /etc/groups file and replaces your encrypted password entries with x. If you add new entries to the /etc/groups file, you can run grpconv again to transfer the new information to /etc/gshadow. It will ignore entries that already have a password of x and convert those that do not. grpunconv restores the encrypted passwords to your /etc/groups file and removes the /etc/gshadow file.

An interpreter for Adobe Systems' PostScript and PDF (Portable Document Format) languages; used for document processing. With - in place of files, standard input is used.

Options

• -- filename arg1 ...
• Take the next argument as a filename, but use all remaining arguments to define ARGUMENTS in userdict (not systemdict) as an array of those strings, before running the file.
• -gnumber1xnumber2
• Specify width and height of device; intended for systems like the X Window System.
• -q
• Quiet startup.
• -rnumber, -rnumber1xnumber2
• Specify X and Y resolutions (for the benefit of devices, such as printers, that support multiple X and Y resolutions). If only one number is given, it is used for both X and Y resolutions.
• -Dname=token, -dname=token
• Define a name in systemdict with the given definition. The token must be exactly one token (as defined by the token operator) and must not contain any whitespace.
• -Dname, -dname
• Define a name in systemdict with a null value.
• -Idirectories
• Adds the designated list of directories at the head of the search path for library files.
• -Sname=string, -sname=string
• Define a name in systemdict with a given string as value.

Special names

• -dDISKFONTS
• Causes individual character outlines to be loaded from the disk the first time they are encountered.
• -dNOBIND
• Disables the bind operator. Useful only for debugging.
• -dNOCACHE
• Disables character caching. Useful only for debugging.
• -dNODISPLAY
• Suppresses the normal initialization of the output device. May be useful when debugging.
• -dNOPAUSE
• Disables the prompt and pause at the end of each page.
• -dNOPLATFONTS
• Disables the use of fonts supplied by the underlying platform (e.g., the X Window System).
• -dSAFER
• Disables the deletefile and renamefile operators and the ability to open files in any mode other than read-only.
• -dWRITESYSTEMDICT
• Leaves systemdict writable.
• -sDEVICE=device
• Selects an alternate initial output device.
• -sOUTPUTFILE=filename
• Selects an alternate output file (or pipe) for the initial output device.

Uncompress files compressed by gzip. See gzip for a list of options.

Compress executables. When run, these files automatically uncompress, thus trading time for space. gzexe creates backup files (filename~), which should be removed after testing the original.

Option

• -d
• Decompress files.

gunzip [options] [files]

zcat [options] [files]

Compress specified files (or read from standard input) with Lempel-Ziv coding (LZ77). Rename compressed file to filename.gz; keep ownership modes and access/modification times. Ignore symbolic links. Uncompress with gunzip, which takes all of gzip's options, except those specified. zcat is identical to gunzip -c and takes the options -fhLV, described here. Files compressed with the compress command can be decompressed using these commands.

Options

• -n, --fast, --best
• Regulate the speed of compression using the specified digit n, where -1 or --fast indicates the fastest compression method (less compression) and -9 or --best indicates the slowest compression method (most compression). The default compression level is -6.
• -a, --ascii
• ASCII text mode: convert end-of-lines using local conventions. This option is supported only on some non-Unix systems.
• -c, --stdout, --to-stdout
• Print output to standard output, and do not change input files.
• -d, --decompress, --uncompress
• Same as gunzip.
• -f, --force
• Force compression. gzip would normally prompt for permission to continue when the file has multiple links, its gz version already exists, or it is reading compressed data to or from a terminal.
• -h --help
• Display a help screen and then exit.
• -l, --list
• Expects to be given compressed files as arguments. Files may be compressed by any of the following methods: gzip, deflate, compress, lzh, and pack. For each file, list uncompressed and compressed sizes (the latter being always -1 for files compressed by programs other than gzip), compression ratio, and uncompressed name. With -v, also print compression method, the 32-bit CRC of the uncompressed data, and the timestamp. With -N, look inside the file for the uncompressed name and timestamp.
• -L, --license
• Display the gzip license and quit.
• -n, --no-name
• When compressing, do not save the original filename and timestamp by default. When decompressing, do not restore the original filename if present, and do not restore the original timestamp if present. This option is the default when decompressing.
• -N, --name
• Default. Save original name and timestamp. When decompressing, restore original name and timestamp.
• -q, --quiet
• Print no warnings.
• -r, --recursive
• When given a directory as an argument, recursively compress or decompress files within it.
• -S suffix, --suffix suffix
• Append .suffix. Default is gz. A null suffix while decompressing causes gunzip to attempt to decompress all specified files, regardless of suffix.
• -t, --test
• Test compressed file integrity.
• -v, --verbose
• Print name and percent size reduction for each file.
• -V, --version
• Display the version number and compilation options.

System administration command. Insert a note in the file /var/log/wtmp; if the system is in runlevel 0 or 6, stop all processes; otherwise, call shutdown -nf.

Options

• -d
• Suppress writing to /var/log/wtmp.
• -f
• Call halt even when shutdown -nf would normally be called (i.e., force a call to halt, even when not in runlevel 0 or 6).
• -n
• Suppress normal call to sync.
• -w
• Suppress normal execution; simply write to /var/log/wtmp.

Print the first few lines (default is 10) of one or more files. If files is missing or -, read from standard input. With more than one file, print a header for each file.

Options

• -c num[bkm], --bytes num
• Print first num bytes or, if num is followed by b, k, or m, first num 512-byte blocks, 1-kilobyte blocks, or 1-megabyte blocks.
• --help
• Display help and then exit.
• -n num, --lines num, -num
• Print first num lines. Default is 10.
• -q, --quiet, --silent
• Quiet mode; never print headers giving filenames.
• -v, --verbose
• Print filename headers, even for only one file.
• --version
• Output version information and then exit.

Examples

Display the first 20 lines of phone_list:

head -20 phone_list

Display the first 10 phone numbers having a 202 area code:

grep '(202)' phone_list | head

host [options] zone [server]

System administration command. Print information about specified hosts or zones in DNS. Hosts may be IP addresses or hostnames; host converts IP addresses to hostnames by default and appends the local domain to hosts without a trailing dot. Default servers are determined in /etc/resolv.conf. For more information about hosts and zones, try Chapters 1 and 2 of DNS and BIND by Paul Albitz and Cricket Liu, published by Anonymous.

Options

• -a
• Same as -t ANY.
• -c class
• Search for specified resource record class (IN, INTERNET, CS, CSNET, CH, CHAOS, HS, HESIOD, ANY, or *). Default is IN.
• -d
• Debugging mode. -dd is a more verbose version.
• -e
• Do not print information about domains outside of specified zone. For hostname queries, do not print "additional information" or "authoritative nameserver."
• -f file
• Output to file as well as standard out.
• -i
• Given an IP address, return the corresponding in-addr.arpa address, class (always PTR), and hostname.
• -l zone
• List all machines in zone.
• -m
• Print only MR, MG, and MB records; recursively expand MR (renamed mail box) and MG (mail group) records to MB (mail box) records.
• -o
• Do not print output to standard out.
• -p [server]
• For use with -l. Query only the zone's primary nameserver (or server) for zone transfers, instead of those authoritative servers that respond. Useful for testing unregistered zones.
• -q
• Quiet. Suppress warning, but not error, messages.
• -r
• Do not ask contacted server to query other servers, but require only the information that it has cached.
• -t type
• Look for type entries in the resource record. type may be A, NS, PTR, ANY, or * (all).
• -u
• Use TCP, not UDP.
• -v
• Verbose. Include all fields from resource record, even time-to-live and class, as well as "additional information" and "authoritative nameservers" (provided by the remote nameserver).
• -vv
• Very verbose. Include information about host's defaults.
• -w
• Never give up on queried server.
• -x
• Allow multiple hosts or zones to be specified. If a server is also specified, the argument must be preceded by -X.
• -A
• For hostnames, look up the associated IP address, and then reverse look up the hostname, to see if a match occurs. For IP addresses, look up the associated hostname, and determine whether the host recognizes that address as its own. For zones, check IP addresses for all hosts. Exit silently if no incongruities are discovered.
• -C
• Similar to -l, but also check to see if the zone's name servers are really authoritative. The zone's SOA (start of authority) records specify authoritative name servers (in NS fields). Those servers are queried; if they do not have SOA records, host reports a lame delegation. Other checks are made as well.
• -D
• Similar to -H but include the names of hosts with more than one address per defined name.
• -E
• Similar to -H but do not treat extra-zone hosts as errors. Extra-zone hosts are hosts in an undefined subdomain.
• -F file
• Redirect standard out to file, and print extra resource record output only on standard out.
• -G zone
• Similar to -H but include the names of gateway hosts.
• -H zone
• Print the number of unique hosts within zone. Do not include aliases. Also list all errors found (extra-zone names, duplicate hosts).
• -I chars
• Do not print warnings about domain names containing illegal characters chars, such as _.
• -L level
• For use with -l. List all delegated zones within this zone, up to level deep, recursively.
• -P servers
• For use with -l. servers should be a comma-separated list. Specify preferred hosts for secondary servers to use when copying over zone data. Highest priority is given to those servers that match the most domain components in a given part of servers.
• -R
• Treat non-fully-qualified hostnames as BIND does, searching each component of the local domain.
• -S
• For use with -l. Print all hosts within the zone to standard out. Do not print hosts within subzones. Include class and IP address. Print warning messages (illegal names, lame delegations, missing records, etc.) to standard error.
• -T
• Print time-to-live values (how long information about each host will remain cached before the nameserver refreshes it).
• -X server
• Specify a server to query, and allow multiple hosts or zones to be specified.
• -Z
• When printing recource records, include trailing dot in domain names, and print time-to-live value and class name.