shell中判斷變量是否爲空

1.變量經過「 」引號引發來

    以下所示，能夠獲得結果爲 is null

    

#!/bin/bash

para1=

if[! -n "$para1"]
then
    echo "is null"

else
    echo "not null"

fi

2.直接經過變量判斷：

    以下所示，獲得的記過爲: is null

#!/bin/bash

para1=

if[!${para1}];then
    echo "is null"
else
    echo "not null"
fi

3.使用test判斷

#!/bin/bash


dmin=
if test -z "$dmin"
then
  echo "dmin is not set!"
else  
  echo "dmin is set !"
fi

4.使用""判斷

#!/bin/bash
dmin=
if [ "$dmin" = "" ]
then
  echo "dmin is not set!"
else  
  echo "dmin is set !"
fi

 

參考資料

CSDN