2.shell编程-函数的高级用法

[root@VM_0_9_centos ~]# test()
> {}
-bash: syntax error near unexpected token `{}‘
[root@VM_0_9_centos ~]# test() {}
-bash: syntax error near unexpected token `{}‘
[root@VM_0_9_centos ~]# test() 
> {
>     echo "test function"
> }
[root@VM_0_9_centos ~]# test
test function
[root@VM_0_9_centos ~]# function greeting
> {
>     echo "hello world"
> }
[root@VM_0_9_centos ~]# greeting 
hello world
[root@VM_0_9_centos ~]# 

#!/bin/bash
#

#运行脚本的进程id，如果脚本名字有nginx字样，也需要把这个过滤掉
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

nohup sh nginx_daemon.sh &

tail -f nohup.out

function name
{
    echo "hello $1"
    echo "hello $2"
}

name derek alice

[root@VM_0_9_centos shell_learn]# function greeting
> {
>     echo "Hello $1"
> }
[root@VM_0_9_centos shell_learn]# 
[root@VM_0_9_centos shell_learn]# greeting derek
Hello derek
[root@VM_0_9_centos shell_learn]# greeting alice
Hello alice
[root@VM_0_9_centos shell_learn]# 

方式一：return

方法二：echo

#!/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 runnig...." || echo "nginx is stop!"

#!/bin/bash
#

function get_users
{
    users=`cat /etc/passwd | cut -d: -f1`
    echo $users
}

user_list=`get_users`

index=1

for user in $user_list
do
    echo "The $index user is: $user"
    index=$(($index+1))
done