如何定时查询某线程的CPU执行时间

 #!/bin/bash

 pid=$(ps -T -p $(pgrep xxx) | grep xxx | gawk -F" " '{print $2}')
 if [ -z $pid ]; then
   echo "can not find xxx"
   exit
 fi
 echo "pid: "$pid
 prev_runtime=
 while true; do
   current_runtime=`cat /proc/$pid/sched | grep exec_run | gawk -F: '{print $2}' | gawk -F"." '{print $1}'`;
   #echo $current_runtime
   delta=$(expr $current_runtime - $prev_runtime)
   echo "rtime:$delta ms/s"
   prev_runtime=$current_runtime
   sleep ;
 done