String Editing (Colon) Operators

When the C shell and bash do history substitutions () they can also edit the substitution. The C shell - but not bash - can also edit variable substitutions (). For instance, in the first example below, when !$ contains /a/b/c, adding the "head" operator :h will give just the head of the pathname, /a/b.

For a complete but very terse list of these operators, see the csh manual page. We hope the examples below will help you understand these useful operators.

• :h gives the head of a pathname (), as follows:
  
  

  % echo /a/b/c /a/b/c % echo !$:h echo /a/b /a/b
  

  That took off the filename and left the header. This also could be used with C shell variables () as:

  % set x = /a/b/c % echo $x /a/b/c % echo $x:h /a/b
  

  
  
  
• :r returns the root of a filename:
  
  

  % echo xyz.c abc.c xyz.c abc.c % echo !$:r echo abc abc
  

  The :r removed the c from the last argument, leaving the root name. This could also be used in C shell variable names:

  % set x = abc.c % echo $x:r abc
  

  
  
  
• :g For more than one name, you can add the g operator to make the operation global. For example:

  (...)	% set x = (a.a b.b c.c) % echo $x:gr a b c

  The :gr operator stripped off all dot () suffixes. By the way, this use of g does not work with the history commands.

  This is the C shell's answer to the basename () command.

• :e returns the extension (the part of the name after a dot). Using csh variables:
  
  

  % set x=(abc.c) % echo $x:e c
  

  No luck using that within history, either.

• :t gives the tail of a pathname - the actual filename without the path:
  
  

  % echo /a/b/c /a/b/c % echo !$:t c
  

  With csh variables:

  % set x=(/a/b/c) % echo $x:t c
  

  And with multiple pathnames, you can do it globally with:

  % set x=(/a/b/c /d/e/f /g/h/i) % echo $x:gt c f i
  

  While the corresponding heads would be:

  % set x=(/a/b/c /d/e/f /g/h/i) % echo $x:gh /a/b /d/e /g/h
  

  
  
  
• :p prints the command, but does not execute it ():
  
  

  % echo * fn1 fn2 fn3 % !:p echo fn1 fn2 fn3
  

  
  
  
• :q prevents further filename expansion, or prints the command as is:
  
  

  % echo * fn1 fn2 fn3 % !:q echo * *
  

  The first command echoed the files in the directory, and when the :q was applied, it echoed only the special character.

• :x is like :q, but it breaks the line into words. That is, when using :q, it is all one word, while :x will break it up into multiple words. [:q and :x are more often used with C shell arrays (). -JP ]

- DR