shell脚本语言之if条件判断语句实例详解

#!/bin/bash
#date：2022-4-13
#描述：if单分支语句示例，判断目录是否存在
read -p "请输入需要判断的目录：" name
if [ ! -d $name ]
    then
        echo "$name目录不存在，正在创建..."
        mkdir -p $name
        echo "$name目录创建完成."
fi
        echo "$name目录已存在，正在退出..."

[root@xiaopeng ~]# cat autostart.sh 
#!/bin/bash 
port=$(nmap -sT 192.168.22.222 | grep tcp | grep http | awk '{print $2}') 
if [ "$port" == "open" ] 
    then 
        echo "$(date) httpd is ok!" >> /tmp/autostart-acc.log 
    else 
        /etc/rc.d/init.d/httpd start &> /dev/nullecho "$(date) restart httpd!!" >> /tmp/autostart-err.log 
fi

#!/bin/bash
#date:2022-4-13
#描述:判断文件类型
read -p "请输入一个文件:" file
if [ -z $file ]
    then
        echo    "错误！输入的文件为空."
elif [ ! -e $file ]
    then
        echo    "错误！输入的文件不存在."
elif [ -f $file ]
    then
        echo    "$file是一个普通文件"
elif [ -d $file ]
    then
        echo    "$file是一个目录"
else
        echo    "$file是其他类型文件"
fi

[root@xiaopeng htdocs]# vim /etc/init.d/apached
#！/bin/bash
# chkconfig: 2345 64 36         
# description: A very fast and reliable SQL database engine
httpd=/usr/local/apache2/bin/apachectl
case $1 in
start)
        $httpd start
        ;;
stop)
        $httpd stop
        ;;
restart)
        $0 stop                 
        sleep 0.05              
        $0 start
        ;;
configtest)                     
$httpd  -t
;;
*)
        echo "usage:$0 start|stop|restart|configtest."
        ;;
esac

[root@xiaopeng conf]# vim  /etc/init.d/nginx
#!/bin/bash
#Author：liu
#chkconfig: 2345 99 33
#description: nginx server control tools
 
ngxc="/usr/local/nginx/sbin/nginx"
ngxc_fpm="/usr/local/php/sbin/php-fpm"
case "$1" in
    start)
        $ngxc -t &> /dev/null
        if [ $? -eq 0 ];then
                $ngxc
                $ngxc_fpm
                echo "nginx service start success!"
        else
                $ngxc -t
        fi
        ;;
    stop)
        $ngxc  -s  stop
        killall  php-fpm
        echo "nginx service stop success!"
        ;;
    restart)
        $0 stop
        $0 start
        ;;
    reload)
        $ngxc -t &> /dev/null
        if [ $? -eq 0 ];then
               $ngxc  -s  reload
                pkill  -HUP  php-fpm
                echo "reload nginx config success!"
        else
                $ngxc -t
        fi
        ;;
    *)
        echo "please input stop|start|restart|reload."
        exit 1
esac