【Redhat Linux】shell 2 流程控制

【流程控制】

【IF THEN】
#!/bin/bash

read -p 'plese input :' var
  
if
elif
else

fi

$$ pid
$* 命令后的参数全部显示一遍
$@ 同上
$# 命令后参数数量
$? 上一条子命令是否执行成功

检查nginx是否开启

#！bin/bash

ps aux |grep nginx |grep -v 'grep'

echo $?

if[$? -ne 0] 
    then
        systemctl start nginx
else
fi

【while】

while :
do
    free
    sleep 29
    clear
done

while [  Scount -le 10 ]
do
    echo Scount
    ((count++))
done

while :
do
    clear
    read -p 'please input your name: 'name
    read -p 'please input your password: ' psd
    if [ -z $name ] || [ -z $psd ]
        then
            continue
    fi

    if [ $name = 'alex' ] && [ $psd = '1234' ]
        then
            echo 'login successful ,welcome'

            while :
            do
                read -p 'please input your cmd: 'cmd
                if [ "$cmd" = 'quit' ]
                    then
                        break
                fi
                $ cmd
            doen
    else
        echo 'ueername or password is error'
    fi
done

【FOR】

for i in {1...253}
do
    ping -cl 192.168.16.$1 &> /dev/null
    if [ $? -ne 0]
        then
            echo "192.168.16.$i is available"
    else
            echo "192.168.16.$i is unavailable"
    fi
done

【case】
#Python 没有此语法
read -p '>>: ' uname
case $uname in
root)
echo "welcome $uname"
;;
seker)
echo "welcome $uname"
;;
default)
echo "welcome $uname"

;;
*)
echo "no kind of user $uname"
esac

【函数】
函数定义：
function abc(){echo 'aaa';echo 'bbbb';}
调用:
abc
set 查看

function install(){
   echo 'install'
}

function start(){
   echo 'start'
}

if [ "$1" = 'install' ]
then
    install

elif [ "$1" = 'start' ]
then
    start
else
    echo 'commond can not found'
fi