Openwrt下获取进程pid的实用shell

摘要: 最近陷入各种基于openwrt的系统中，有的是原版opwrt，有的是修改过的openwrt，以致有的系统命令被阉割，有的系统命令被保留，导致shell在一类设备上运行ok，在另类设备上运行不ok。查询进程号pid就是一个例子。
查询进程pid常用shell命令：ps，pgrep，top
其中ps aux和ps -ef不是全部设备都支持；
pgrep "XXX"也不太灵光，比如我自己的后台脚本程序就靠名字拿不到pid；
最后是用的top命令来兼顾所有的不同openwrt设备都能拿到程序的进程号。

查询某个名字进程的pid shell函数如下：
函数成功会返回当前进程的pid，如果不在该进程返回null，没有传入程序名称返回-1
#!/bin/sh
GetPidByCommand(){
if [ ! -n "${1}" ]
then
echo "-1"
fi

ptop=$(top -n 1 |grep "${1}" |grep -v "grep ${1}")
pid=""

startpos=0
stringlen=${#ptop}
startstatus=0

while [ 1 ]
do
if [ ${startpos} -ge ${stringlen} ]
then
break
fi

currchar=${ptop:${startpos}:1}

if [ "${currchar}" = "0" ] || [ "${currchar}" = "1" ] || [ "${currchar}" = "2" ] || [ "${currchar}" = "3" ] || [ "${currchar}" = "4" ] || [ "${currchar}" = "5" ] || [ "${currchar}" = "6" ] || [ "${currchar}" = "7" ] || [ "${currchar}" = "8" ] || [ "${currchar}" = "9" ]
then
if [ ${startstatus} -eq 0 ]
then
startstatus=1
fi

pid=${pid}${currchar}
elif [ ${startstatus} -eq 1 ]
then
break
fi

startpos=$(expr ${startpos} + 1 )
done

echo ${pid}

}

pid=$(GetPidByCommand "Test001")

echo "Test001 pid = ${pid}"

exit 0

最后发现：pgrep -f "XXX"可以搞定 囧
Usage: pgrep [-flnovx] [-s SID|-P PPID|PATTERN]

Display process(es) selected by regex PATTERN

-l      Show command name too
-f      Match against entire command line
-n      Show the newest process only
-o      Show the oldest process only
-v      Negate the match
-x      Match whole name (not substring)
-s      Match session ID (0 for current)
-P      Match parent process ID