[原创]Bash中的$*和$@的区别

        在Bash脚本中,$*和$@都用于表示执行脚本时所传入的参数。先通过一个例子看看他们的区别:

#!/bin/bash
# testvar.sh
echo "-------------ISF is set to \"-seperator\" ------------"
IFS="-seperator";  # 注意 seperator前有一个减号(-)
for i in "$@"; do echo "@ '$i'"; done
for i in "$*"; do echo "* '$i'"; done

echo "-------------ISF is set to null ------------------------"
IFS=
for i in "$@"; do echo "@ '$i'"; done
for i in "$*"; do echo "* '$i'"; done

echo "-------------ISF is unset ------------------------"
unset IFS
for i in "$@"; do echo "@ '$i'"; done
for i in "$*"; do echo "* '$i'"; done


echo "---------$* and $@ are not put into double quotes(\"\")-------"
for i in $@; do echo "@ '$i'"; done
for i in $*; do echo "* '$i'"; done

执行的结果如下:

-------------ISF is set to "-seperator" ------------

@ 'aa'

@ 'bb'

@ 'cc'

* 'aa-bb-cc'

-------------ISF is set to null ------------------------

@ 'aa'

@ 'bb'

@ 'cc'

* 'aabbcc'

-------------ISF is unset ------------------------

@ 'aa'

@ 'bb'

@ 'cc'

* 'aa bb cc'

---------aa bb cc and aa bb cc are not put into double quotes("")-------

@ 'aa'

@ 'bb'

@ 'cc'

* 'aa'

* 'bb'

* 'cc'


由此可见,
1) 当不加双引号("")时, $*,$@被展开时的行为是一样的;
2) 当$*,$@都被放到双引号("")内;
    2.1) 如果设置了变量IFS的值并且该值非空, 则$*被展开时使用${IFS}的第一个字符将所有参数(除了参数$0)连接起来, 即"$1c$2c$3c...",其中c表示${IFS}的第一个字符;
    2.2) 如果变量IFS为空, 则$*被展开时只是将所有参数(除了参数$0)简单连接起来, 即 “$1$2$3..."
    2.3)如果变量IFS没有被定义, 则$*被展开时使用空格字符将所有参数(除了参数$0) 连接起来, 即"$1 $2 $3 ..."
    但$@的展开和没有加双引号的情形是一致的。

 

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