linux - 在 bash 脚本中使用它。

Question

这里检查的 if [[ -z $1 ]] 语句到底是什么？

每当我运行时，它都会输出如下:

[root@localhost ~]# sh script.sh

No argument is given

#!/bin/bash

if [[ -z $1 ]]; then

echo "No argument is given"


elif [ "$1" == "testfile" ] ; then

echo "Right argument is given"

else

echo "Wrong argument is given"

fi

Answer 1

参见man bash:

[[ expression ]]

Return a status of 0 or 1 depending on the evaluation of the conditional expression

以及下文

-z string

True if the length of string is zero.