Unix in a Nutshell, 4th Edition

Variable Modifiers

Except for $? var, $?0, $# var, $% var, $#, $$, $?, $!, $_, and $<, the variable substitutions in the preceding section may be followed by one of these modifiers (when braces are used, the modifier goes inside them):

:r	Return the variable’s root (the portion before the last dot).
:e	Return the variable’s extension.
:h	Return the variable’s header (the directory portion).
:t	Return the variable’s tail (the portion after the last slash).
:gr	Return all roots.
:ge	Return all extensions.
:gh	Return all headers.
:gt	Return all tails.
:q	Quote a wordlist variable, keeping the items separate. Prevents further substitution. Useful when the variable contains filename metacharacters that should not be expanded.
:x	Quote a pattern, expanding it into a wordlist.

Examples using pathname modifiers

The following table shows the effect of pathname modifiers if the aa variable is set as follows:

    set aa=(/progs/num.c /book/chap.ps)

Variable portion	Specification	Output result
Normal variable	echo $aa	/progs/num.c /book/chap.ps
Second root	echo $aa[2]:r	/book/chap
Second header	echo $aa[2]:h	/book
Second tail	echo $aa[2]:t	chap.ps
Second extension	echo $aa[2]:e	ps
Root	echo $aa:r	/progs/num /book/chap.ps
Global root	echo $aa:gr	/progs/num /book/chap
Header	echo $aa:h	/progs /book/chap.ps
Global header	echo $aa:gh	/progs /book
Tail	echo $aa:t	num.c /book/chap.ps