What's the difference between $@ and $* in UNIX? When echoed in a script, they both seem to produce the same output.
4 Answers
Please see the bash man page under Special Parameters.
Special Parameters The shell treats several parameters specially. These parameters may only be referenced; assignment to them is not allowed. * Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, it expands to a sin‐ gle word with the value of each parameter separated by the first character of the IFS special variable. That is, "$*" is equiva‐ lent to "$1c$2c...", where c is the first character of the value of the IFS variable. If IFS is unset, the parameters are sepa‐ rated by spaces. If IFS is null, the parameters are joined without intervening separators. @ Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, each parameter expands to a separate word. That is, "$@" is equivalent to "$1" "$2" ... If the double-quoted expansion occurs within a word, the expansion of the first parameter is joined with the begin‐ ning part of the original word, and the expansion of the last parameter is joined with the last part of the original word. When there are no positional parameters, "$@" and $@ expand to nothing (i.e., they are removed). 
Comments
One difference is in how they handle the IFS variable on output.
#!/bin/sh echo "unquoted asterisk " $* echo "quoted asterisk $*" echo "unquoted at " $@ echo "quoted at $@" IFS="X" echo "IFS is now $IFS" echo "unquoted asterisk " $* echo "quoted asterisk $*" echo "unquoted at " $@ echo "quoted at $@" If you run this like this: ./demo abc def ghi, you get this output:
unquoted asterisk abc def ghi quoted asterisk abc def ghi unquoted at abc def ghi quoted at abc def ghi IFS is now X unquoted asterisk abc def ghi quoted asterisk abcXdefXghi unquoted at abc def ghi quoted at abc def ghi Notice that (only) the "quoted asterisk" line shows an X between each "word" after IFS is changed to "X". If the value of IFS contains multiple characters, only the first character is used for this purpose.
This feature can also be used for other arrays:
$ array=(123 456 789) $ saveIFS=$IFS; IFS="|" $ echo "${array[*]}" 123|456|789 $ IFS=$saveIFS answered Jul 22, 2010 at 10:54
Dennis Williamson
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Comments
for i in "$@" do echo $i # loop $# times done for i in "$*" do echo $i # loop 1 times done 
Comments
It's safer to use "$@" instead of $*. When you use multiword strings as arguments to a shell script, it's only "$@" that interprets each quoted argument as a separate argument.
As the output above suggests, if you use $*, the shell makes a wrong count of the arguments.
$@and$*(even if the question doesn't). The crucial difference is in the behaviour under quotes - the difference between"$*"and"$@".