Command-Line Switches

Command-line switches are command-line arguments that begin with a - character, and precede the list of recipients (if any). The forms for command-line switches, where X is a single letter, are:

-X Boolean switch -Xarg switch with argument

All switches are single letters. The complete list is shown in Table 36.2.

Command-Line Switches
Switch		Version	Description
`-B`	-B	and above	Specify message body type
`-b`	-b	All versions	Set operating mode
`-ba`	-ba	Not V8.1- V8.6	Use ARPAnet/Grey Tutorial protocols
`-bD`	-bD	and above	Run as a daemon, but don't fork
`-bd`		All versions	Run as a daemon
`-bH`		and above	Purge persistent host status
`-bh`	-bh	and above	Print persistent host status
`-bi`		All versions	Initialize alias database
`-bm`	-bm	All versions	Be a mail sender
`-bp`		All versions	Print the queue
`-bs`	-bs	All versions	Run SMTP on standard input
`-bt`	"Overview"	All versions	Rule testing mode
`-bv`	-bv	All versions	Verify: don't collect or deliver
`-bz`	-bz	Not V8	Freeze the configuration file
`-C`	-C	All versions	Location of configuration file
`-c`	HoldExpensive (c)	Deprecated	Set HoldExpensive (c) option to true
`-d`	"The Syntax of -d"	All versions	Enter debugging mode
`-E`	-E	Sony NEWS only	Japanese font conversion
`-e`	ErrorMode (e)	Deprecated	Set the ErrorMode (e) option's mode
`-F`	-F	All versions	Set the sender's full name
`-f`	-f and -r	All versions	Set sender's address
`-h`	-h	Deprecated	Minimum hop count
`-I`	-I	Deprecated	Synonym for `-bi`
`-i`	-i	Deprecated	Set the IgnoreDots (i) option to true
`-J`	-J	Sony NEWS only	Japanese font conversion
`-M`	"Command-Line Definitions"	and above	Define a macro on the command line
`-m`	MeToo (m)	All versions	Set the MeToo (m) option to true
`-N`	-N	and above	Specify DSN NOTIFY information
`-n`	"Prevent Aliasing with -n"	All versions	Don't do aliasing
`-O`	"Command-Line Options"	and above	Set a multicharacter option
`-o`		All versions	Set a single-character option
`-p`	-p	and above	Set protocol and host
`-q`		All versions	Process the queue
`-R`	-R	and above	DSN what to return on a bounce
`-r`		Deprecated	Synonym for `-f`
`-s`	SaveFromLine (f)	Deprecated	Set the SaveFromLine (f) option to true
`-T`	QueueTimeout (T)	Deprecated	Set QueueTimeout (T) option
`-t`	-t	All versions	Get recipients from message header
`-U`	-U	and above	This is the initial MUA to MTA submission
`-V`	-V	and above	Specify the ENVID string
`-v`		All versions	Run in verbose mode
`-X`	"Log Transactions with -X"	and above	Log transactions
`-x`	-x	and above	Ignored

Some switches are called Boolean because they are either true or false. The -v switch, for example, is Boolean because it puts sendmail into verbose mode if it is present (true). If it is absent (false), sendmail does not run in verbose mode.

Some switches take arguments. The -C switch, for example, tells sendmail where to find its configuration file. When a switch takes an argument, the argument may immediately follow the letter or be separated from it with whitespace: [2]

[2] Prior to V8 sendmail, whitespace was not allowed between the letter and the argument.

-Ctest.cf good -C test.cf also good

The only exception to this rule is the -d command-line switch (set debugging mode). It may not have whitespace between the letter and the arg.

Some switches, such as -q (process the queue), can either be Boolean or take an argument:

-q boolean -q1h with argument

The position of switches in the command line is critical. If any follow the list of recipients, they are wrongly taken as mail addresses and lead to bounced mail. But the order in which switches appear prior to the recipients is not important. That is, they may appear in any order without changing the behavior of sendmail.

An undefined switch letter causes the following error to be printed and sendmail to immediately exit:

sendmail: illegal option - bad letter here

The special switch -- can be used to delimit the switches from the list of recipients:

% /usr/lib/sendmail -- -jim

Here, the recipient is -jim. To prevent the - of -jim from being wrongly interpreted as indicating a switch, the special switch -- is used to mark the end of all switches. [3]

[3] Under pre-V8 sendmail, recipient names could never begin with a -C, -b, -d, -q, or -Z. If any did, they were wrongly interpreted as switches during preprocessing.