linux shell 中判断字符串为空的正确方法

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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