获取进程运行时间

#!/bin/bash
function show_elapsed_time()
{
        user_hz=$(getconf CLK_TCK) #mostly it's 100 on x86/x86_64
        pid=$1
        jiffies=$(cat /proc/$pid/stat | cut -d" " -f22)
        sys_uptime=$(cat /proc/uptime | cut -d" " -f1)
        last_time=$(( ${sys_uptime%.*} - $jiffies/$user_hz ))
        lastday=$(( $last_time/3600/24 ))
        lasthour=$(( ($last_time-$lastday*3600*24)/3600 ))
        lastminute=$(( ($last_time-$lastday*3600*24 - $lasthour*3600)/60 ))
        lastsecond=$(( ($last_time - $lastday*3600*24 - $lasthour*3600 - $lastminute*60) ))
        echo "the process $pid lasts for $last_time seconds. That is $lastday days $lasthour hours $lastminute minutes $lastsecond second."
}

if [ $# -ge 1 ];then
        for pid in $@
        do
                show_elapsed_time $pid
        done
fi

while read pid
do
        show_elapsed_time $pid
done