$*与$@的异同

两者都代表bash命令行参数，在没有用双引号括起来的时候，两者效果一样

但是两者若被双引号括起来，就有不同了

$*会显示出参数见的分隔符，而$@则不会。这是因为前者被解读为一个整体字符串，而后在解读为一个个分开的字符串

参考文献：http://bash.cyberciti.biz/guide/$IFS

IFS Effect On The Values of "$@" And "$*"

• $@ and $* are special command line arguments shell variables.
• The $@ holds list of all arguments passed to the script.
• The $* holds list of all arguments passed to the script.
• Create a shell script called ifsargs.sh:

#!/bin/bash
# ifsargs.sh - Cmd args - positional parameter demo
echo "Command-Line Arguments Demo"
echo "*** All args displayed using \$@ positional parameter ***"
echo $@
echo "*** All args displayed using \$* positional parameter ***"
echo $*

Save and close the file. Run it as follows:

chmod +x ifsargs.sh
./ifsargs.sh honda yamaha harley-davidson kawasaki

Sample outputs:

Command-Line Arguments Demo
*** All args displayed using $@ positional parameter ***
honda yamaha harley-davidson kawasaki
*** All args displayed using $* positional parameter ***
honda yamaha harley-davidson kawasaki

• As you can see, the values of $@ and $* are same.
• However, the values of "$@" and "$*" are different (note double quotes).
• Edit ifsargs.sh as follows

#!/bin/bash
# ifsargs.sh - Cmd args - positional parameter demo
 
#### Set the IFS to | ####
IFS='|'
 
echo "Command-Line Arguments Demo"
 
echo "*** All args displayed using \$@ positional parameter ***"
echo "$@"        #*** double quote added ***#
 
echo "*** All args displayed using \$* positional parameter ***"
echo "$*"        #*** double quote added ***#

Save and close the file. Run it as follows:

./ifsargs.sh honda yamaha harley-davidson kawasaki

Sample outputs:

Command-Line Arguments Demo
*** All args displayed using $@ positional parameter ***
honda yamaha harley-davidson kawasaki
*** All args displayed using $* positional parameter ***
honda|yamaha|harley-davidson|kawasaki

• $@ expanded as "$1" "$2" "$3" ... "$n"
• $* expanded as "$1y$2y$3y...$n", where y is the value of IFS variable i.e. "$*" is one long string and $IFS act as an separator or token delimiters.