#!/bin/bash
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

# sh testvar.sh 11 22 33
-------------ISF is set to "-seperator" ------------
@ '11'
@ '22'
@ '33'
* '11-22-33'
-------------ISF is set to null ------------------------
@ '11'
@ '22'
@ '33'
* '112233'
-------------ISF is unset ------------------------
@ '11'
@ '22'
@ '33'
* '11 22 33'
---------11 22 33 and 11 22 33 are not put into double quotes("")-------
@ '11'
@ '22'
@ '33'
* '11'
* '22'
* '33'

• 当不加双引号("")时, $*,$@被展开时的行为是一样的;
• 当$*,$@都被放到双引号("")内;
  • 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；
  • 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$3..."
  • 如果变量IFS没有被定义, 则$*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 ..."