函数定义和使用

#!/bin/bash#实时监控nginx进程的状态this_pid=$$while true    do    ps -ef | grep nginx | grep -v grep | grep -v $this_pid &> /dev/null        if [ $? -eq 0 ];then    	echo "Nginx is running well"    	sleep 3    else    	systemctl start nginx    	echo "Nginx is down,Start it...."    fi    done复制代码

向函数传递参数

#!/bin/bash#计算器function calcu{	case $2 in		+)			echo "`expr $1 + $3`"			;;		-)			echo "`expr $1 - $3`"			;;		\*)			echo "`expr $1 \* $3`"			;;		/)			echo "`expr $1 / $3`"			;;	esac}calcu $1 $2 $3复制代码

函数返回值

#!/bin/bash#this_pid=$$function is_nginx_running{	ps -ef | grep nginx | grep -v grep | grep -v $this_pid &> /dev/null	if [ $? -eq 0 ];then		return	else		return 1	fi}is_nginx_running && echo "Nginx is running" || echo "Nginx is stoped"复制代码

#!/bin/bash#function get_users{	users=`cat /etc/passwd | cut -d: -f1`	echo $users}user_list=`get_users`index=1for u in $user_listdo	echo "The $index user is : $u"	index=$(($index+1))done复制代码

局部变量和全局变量

#!/bin/bash#var1="Hello world"function test{	local var2=87}testecho $var1echo $var2复制代码

函数库

#!/bin/bash#. /root/lesson/3.5/lib/base_functionadd 12 23reduce 90 30multiple 12 12divide 12 2复制代码

function add{	echo "`expr $1 + $2`"}function reduce{	echo "`expr $1 - $2`"}function multiple{	echo "`expr $1 \* $2`"}function divide{	echo "`expr $1 / $2`"}function sys_load{	echo "Memory Info"	echo	free -m	echo		echo "Disk Usage"	echo	df -h	echo}复制代码