Bash 在变量中存储命令 PID 并终止进程
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Bash store command PID in variable and kill process
提问by ogs
I would like to use a shell script in order to establish ethernet connection.
我想使用 shell 脚本来建立以太网连接。
I am using a function implemented as :
我正在使用一个实现为的函数：
function connec()
{
ip link set eth0 up
sleep 5
udhcpc -i eth0
pid=$$
echo $pid
ps
kill -9 $pid
}
However, the script returns :
但是，脚本返回：
743
743 root 2704 S {script.sh} /bin/bash ./script.sh connect
767 root 2200 S udhcpc -i eth0
Killed
I don't succeed in store 767 rather than 743. I also tried by using $! but in that specific case "echo $pid" returns 0.
我在商店 767 而不是 743 中没有成功。我也尝试使用 $! 但在这种特定情况下，“echo $pid”返回 0。
回答by paxdiablo
$$is the currentprocess which means the script is killing itself. You can get the process ID of the last process you started in the background, with $!but it appears you're not actually starting one of those.
$$是当前进程，这意味着脚本正在杀死自己。您可以获得在后台启动的最后一个进程的进程 ID，$!但看起来您实际上并没有启动其中一个。
With your code segment:
使用您的代码段：
udhcpc -i eth0
pid=$$
the pid=line will only be executed when udhcpcexits (or daemonises itself, in which case neither $$nor $!will work anyway), so there's zero point in trying to kill of the process.
该pid=行只会在udhcpc退出时执行（或守护进程本身，在这种情况下既$$不会也$!不会工作），因此尝试终止进程是零点。
To run it in the background and store its process ID, so you can continue to run in the parent, you could use something like:
要在后台运行它并存储其进程 ID，以便您可以继续在父进程中运行，您可以使用类似的方法：
udhcpc -f -i eth0 &
pid=$!
and you're using -fto run in foreground in that case, since you're taking over the normal job control.
-f在这种情况下，您使用在前台运行，因为您正在接管正常的作业控制。
Or, alternatively, since udhcpccan create its ownPID file, you can use something like:
或者，由于udhcpc可以创建自己的PID 文件，您可以使用以下内容：
udhcpc -i eth0 -p /tmp/udhcpc.eth0.pid
pid=$(cat /tmp/udhcpc.eth0.pid)
