Bash: Difference between $@ and $*

Problem

What's the difference between $@ and $*?

Solution

As a rule of thumb, always use "$@". This preserves whitespace, keeps arguments intact and is normally desired. Example:

$ set -- foo bar  # Two arguments `foo' and `bar'
$ for i in "$@"; do echo $i; done
foo
bar
$ set -- 'foo bar'  # Single argument 'foo bar'
$ for i in "$@"; do echo $i; done
foo bar

The table below shows all different combinations of the example above. And the result is that "$@" is most intuitive. Also it appears "$@" is the default behaviour of the empty for-loop: for i; do echo $i; done.

arguments	for i ..; do echo $i; done
	in $@	in "$@"	in $*	in "$*"	(empty)
# Two arguments `foo' and `bar' set -- foo bar	foo bar	foo bar	foo bar	foo bar	foo bar
# One argument `foo bar' set -- 'foo bar'	foo bar	foo bar	foo bar	foo bar	foo bar

Table 1: Example output of $@, "$@", $* and "$*" in for-loop. The preferred notation in "$@" preserves whitespace and keeps arguments intact.

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