BASH练习第三课

写一个脚本，完成如下功能：

（1）显示当前系统上每一个进程及其进程号，而后提示用户输入一个进程号，如果用户输入的进程号错误，而说明其错误，并提醒用户重新输入；

（2）显示用户所选进程的state, PPID和RSS及期对应的值；

#!/bin/bash

exec 2>>/dev/null
#Phase.1 show all process,and get the PID from user
ps -ef
i=0
echo please enter the PID you want to query
while [ "$i" -ne 1 ];
do
read pid
ps -ef | awk '{print $2}' | grep -w $pid >/dev/null
if [ $? -eq 0 ];then
#echo $pid
let i=$i+1
else
echo the PID you input does not exist,please input the PID again
fi
done
#echo $i

#Phase.2 ouput the PID PPID RSS of the process which the PID that user input

STAT=` ps aux |grep  -w $pid  | grep -v grep | awk '{print $8}'`
PPID=` ps -ef |grep  -w $pid  | grep -v grep | awk '{print $3}'`
RSS=` ps aux |grep  -w $pid  | grep -v grep | awk '{print $6}'`

echo the process ID is $pid:STAT=$STAT,PPID=$PPID,RSS=$RSS