Linux之shell腳本for、while、case語句的高級用法

1、case語句的用法：

[root@ELK-chaofeng test]# cat test3.sh
#!/bin/bash

while true ;do
read -p "please input the menu:cpu,mem,disk,quit: " variable
case $variable in
        cpu) lscpu
        break
        ;;
        mem) free -m
        break
        ;;
        disk) fdisk -l /dev/[shv]d[a-z][0-9]
        break
        ;;
        *) echo "error,again"
        ;;
esac
done

看一下效果

 

現在我們來編寫一個服務框架：

[root@ELK-chaofeng init.d]# cat testservice 
#!/bin/bash
#
#chkconfig: 2345 60 60
#description: test service script
#
prog=$(basename $0)
lockfile=/var/lock/subsys/${prog}
case $1 in
start)
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                touch $lockfile
                echo "service $prog start"
        fi
;;
stop)
        if [ -f $lockfile ];then
                rm -rf $lockfile
                echo "service $prog stop"
        else
                echo "service $prog stop"
        fi
;;
restart)
        if [ -f $lockfile ];then
                rm -rf $lockfile && touch $lockfile
                echo "service $prog restart"
        else
                touch $lockfile
                echo "service $prog start"
        fi
;;
status)
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                echo "service $prog is not running"
        fi
;;
*)
        echo "usage: $prog {start|restart|stop|status}"
;;
esac

然后chkconfig添加至service服務管理。現在看一下效果：

[root@ELK-chaofeng init.d]# chkconfig --add testservice 
[root@ELK-chaofeng init.d]# chkconfig --list testservice 

Note: This output shows SysV services only and does not include native
      systemd services. SysV configuration data might be overridden by native
      systemd configuration.

      If you want to list systemd services use 'systemctl list-unit-files'.
      To see services enabled on particular target use
      'systemctl list-dependencies [target]'.

testservice     0:off   1:off   2:on    3:on    4:on    5:on    6:off
[root@ELK-chaofeng init.d]# service testservice status
service testservice is running
[root@ELK-chaofeng init.d]# service testservice stop
service testservice stop
[root@ELK-chaofeng init.d]# service testservice start
service testservice start
[root@ELK-chaofeng init.d]# service testservice status
service testservice is running
[root@ELK-chaofeng init.d]# service testservice stop
service testservice stop
[root@ELK-chaofeng init.d]# service testservice status
service testservice is not running
[root@ELK-chaofeng init.d]# service testservice restart
service testservice start
[root@ELK-chaofeng init.d]# service testservice status
service testservice is running

case總結：

　　case支持glob風格的通配符：、

　　　　*：任意長度的任意字符；

　　　　？：任意單個字符；

　　　　[ ]：范圍內任意單個字符；

　　　　a|b：a或b

現在我們使用函數來改寫上面的腳本：

 

#!/bin/bash
#
#chkconfig: 2345 60 60
#description: test service script
#
prog=$(basename $0)
lockfile=/var/lock/subsys/${prog}
start(){
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                touch $lockfile
                echo "service $prog start"
        fi
}
stop() {
        if [ -f $lockfile ];then
                rm -rf $lockfile
                echo "service $prog stop"
        else
                echo "service $prog stop"
        fi
}
        else
                touch $lockfile
                echo "service $prog start"
        fi
}
stop() {
        if [ -f $lockfile ];then
                rm -rf $lockfile
                echo "service $prog stop"
        else
                echo "service $prog stop"
        fi
}
status() {
        if [ -f $lockfile ];then
                echo "service $prog is running"
        else
                echo "service $prog is not running"
        fi
}
usage () {
        echo "usage: $prog {start|restart|stop|status}"
}
case $1 in
start)
        start
;;
stop)
        stop
;;
restart)
        stop
        start
;;
status)
        status
;;
*)
        usage
;;
esac

 

2、for語句的高級用法：

#!/bin/bash
# print 9*9 
for ((k=1;k<=9;k++));do
        for ((i=1;i<=k;i++));do
                echo -e -n "${i}X${k}=$[${i}*${k}]\t"
        done
        echo ""    #huan hang
done

看一下效果：

3、while語句的高級用法

#!/bin/bash
while read VARIABLE;do
        userID=`echo $VARIABLE | cut -d':' -f 3`
        userUS=`echo $VARIABLE | cut -d':' -f 1`
        usershell=`echo $VARIABLE | cut -d':' -f 7`
        if [ $[$userID%2] -eq 0 ];then
                echo "$userID,$userUS,$usershell"
        fi
done < /etc/passwd

看一下效果：