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Top Forums Shell Programming and Scripting What's the difference between $* and $@ ? Post 302625159 by Skrynesaver on Tuesday 17th of April 2012 10:44:25 AM
Old 04-17-2012
When I call this file
Code:
#!/bin/bash

echo -e "With \$* I have to chose all or nothing"
echo "ALL"
for i in "$*" ; do
    echo -e "\t$i"
done
echo  "NOTHING"
for i in $* ; do
    echo -e "\t$i"
done
echo -e "Whereas with \$@ I get my parameters as the user intended (or at any rate as they sent them to me ;) )"
for i in "$@" ; do
    echo -e "\t$i"
done

as follows
Code:
~/tmp/tmp.sh "It is vital this remains intact" but that these are separate parameters

I get the following
Code:
With $* I have to chose all or nothing
ALL
  It is vital this remains intact but that these are separate parameters
NOTHING
  It
  is
  vital
  this
  remains
  intact
  but
  that
  these
  are
  separate
  parameters
Whereas with $@ I get my parameters as the user intended (or at any rate as they sent them to me ;) )
  It is vital this remains intact
  but
  that
  these
  are
  separate
  parameters

Does that make things clearer?
These 2 Users Gave Thanks to Skrynesaver For This Post:
 

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SHELL-QUOTE(1)						User Contributed Perl Documentation					    SHELL-QUOTE(1)

NAME
shell-quote - quote arguments for safe use, unmodified in a shell command SYNOPSIS
shell-quote [switch]... arg... DESCRIPTION
shell-quote lets you pass arbitrary strings through the shell so that they won't be changed by the shell. This lets you process commands or files with embedded white space or shell globbing characters safely. Here are a few examples. EXAMPLES
ssh preserving args When running a remote command with ssh, ssh doesn't preserve the separate arguments it receives. It just joins them with spaces and passes them to "$SHELL -c". This doesn't work as intended: ssh host touch 'hi there' # fails It creates 2 files, hi and there. Instead, do this: cmd=`shell-quote touch 'hi there'` ssh host "$cmd" This gives you just 1 file, hi there. process find output It's not ordinarily possible to process an arbitrary list of files output by find with a shell script. Anything you put in $IFS to split up the output could legitimately be in a file's name. Here's how you can do it using shell-quote: eval set -- `find -type f -print0 | xargs -0 shell-quote --` debug shell scripts shell-quote is better than echo for debugging shell scripts. debug() { [ -z "$debug" ] || shell-quote "debug:" "$@" } With echo you can't tell the difference between "debug 'foo bar'" and "debug foo bar", but with shell-quote you can. save a command for later shell-quote can be used to build up a shell command to run later. Say you want the user to be able to give you switches for a command you're going to run. If you don't want the switches to be re-evaluated by the shell (which is usually a good idea, else there are things the user can't pass through), you can do something like this: user_switches= while [ $# != 0 ] do case x$1 in x--pass-through) [ $# -gt 1 ] || die "need an argument for $1" user_switches="$user_switches "`shell-quote -- "$2"` shift;; # process other switches esac shift done # later eval "shell-quote some-command $user_switches my args" OPTIONS
--debug Turn debugging on. --help Show the usage message and die. --version Show the version number and exit. AVAILABILITY
The code is licensed under the GNU GPL. Check http://www.argon.org/~roderick/ or CPAN for updated versions. AUTHOR
Roderick Schertler <roderick@argon.org> perl v5.16.3 2010-06-11 SHELL-QUOTE(1)
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