shell判断变量是否为空

1.判断变量

read -p "input a word :" word

if  [ ! -n "$word" ] ;then

    echo "you have not input a word!"

else

    echo "the word you input is $word"

fi

 

2.判断输入参数

#!/bin/bash

if [ ! -n "$1" ] ;then

    echo "you have not input a word!"

else

    echo "the word you input is $1"

fi

下面是我在某项目中写的一点脚本代码， 用在系统启动时:

#! /bin/bash
echo "Input Param Is [$1]"
if [ ! -n "$1" ] ;then

 echo "you have not input a null word!"

 ./app1;./app12;./app123

elif [ $1 -eq 2 ];then

 ./app12;./app123

elif [ $1 -eq 90 ];then

 echo "yy";

fi