转自：http://www.cnblogs.com/cute/archive/2011/08/26/2154137.html

help命令可以查看帮助

help test

 

正确做法：

 

#!/bin/sh

STRING=

if [ -z "$STRING" ]; then 

    echo "STRING is empty"  fi

if [ -n "$STRING" ]; then 

    echo "STRING is not empty"  fi

 

root@james-desktop:~# ./zerostring.sh 

STRING is empty

-------------------------------------------------------------------------

错误做法：

#!/bin/sh

STRING=

if [ -z $STRING ]; then 

    echo "STRING is empty"  fi

if [ -n $STRING ]; then 

    echo "STRING is not empty"  fi 

输出错误结果：

root@james-desktop:~# ./zerostring.sh 

STRING is empty  STRING is not empty