bash笔记

语法

常用

判断是否为空的方法

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

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

直接通过变量判断

#!/bin/sh
para1=
if [ ! $para1 ]; then
  echo "IS NULL"
else
  echo "NOT NULL"
fi 

使用test判断

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

使用""判断

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