思路：nginx启动后会有nginx.pid文件在指定位置下，通过判断该文件是否存在。决定nginx是否已经启动。

#!/bin/bash

#this is my first try to test write a shell to control nginx daemon

#History 2015-08-04 masterliu

PATH=/usr/bin/:/usr/local/bin:/bin:/usr/sbin:/usr/local/sbin:/sbin:~/bin

export PATH

#this file could be configured in nginx.conf

PIDfile=/usr/local/nginx/logs/nginx.pid

Nginxd=/usr/local/nginx/sbin/nginx

function start(){

        if [ -e $PIDfile ];then

        echo -e "nginx has already started\t\t[OK]" && exit 0

        fi

        $Nginxd &> /dev/null

        if [ $? = 0 ];then

                echo -e "nginx has started\t\t[OK]"

        else

                echo -e " nginx start failed\t\t[FAILED]"

        fi

}

function stop(){

        if [ ! -e $PIDfile ];then

                echo -e "nginx has already stopped\t\t[OK]" && exit 0

        fi

        #killall nginx

         $Nginxd -s stop &> /dev/null

        sleep 2

        if [ ! -e $PIDfile ];then

                echo -e "nginx has stopped\t\t[OK]";

        fi

}

function reload(){

        if [ ! -e $PIDfile ];then

                echo -e "nginx hasn't start\t\t[OK]" && exit 0

        fi

        $Nginxd -s reload && echo -e "nginx has reload\t\t[OK]" && exit 0

}

function status(){

        if [ ! -e $PIDfile ];then

                echo -e " nginx hasn't run\t\t[OK]"

        else

                echo -e " nginx is running\t\t[OK]"

        fi

}

case "$1" in

start)

        start

;;

stop)

        stop

;;

restart)

        stop;

        start;

;;

status)

        status

;;

reload)

        reload

;;

*)

        echo -e "\t start|stop|restart|status|reload\t"

;;

esac

来自：http://my.oschina.net/lsfop/blog/488185