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