9.6 String Editing (Colon) Operators

When the C shell and bash do history substitutions (11.7) they can also edit the substitution. The C shell - but not bash - can also edit variable substitutions (6.8). 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 (14.2), 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 (47.5) 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 (45.18) 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 (11.10):

  % 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 (47.5). -JP ]