Perl fork and kill - kill(0, $pid) 总是返回 1，并且不能杀死孩子 [英] Perl fork and kill - kill(0, $pid) always returns 1, and can't kill the child

问题描述

我正在 Linux 主机上运行 perl 脚本.我正在尝试编写一个分叉脚本，其中孩子启动一个需要永远的程序，而父母在 5 秒后超时，杀死孩子.这是我所拥有的:

I am running a perl script on a Linux host. I'm trying to write a script that forks, where the child starts a program that takes forever and the parent times out after 5 seconds, killing the child. Here is what I have:

my $start = time();
my $timeOut = 5;

my $childPid = fork();
if ($childPid) {
    # I am the parent, and $childPid is my child
    while (kill(0, $childPid)) {
        if (time() > $start + $timeOut) {
            $numKilled = kill(SIGTERM, $childPid);
            printf("numKilled: %s\n", $numKilled);
        }
        sleep 1;
    }
}
else {
    # I am the child - do something that blocks forever
    `adb -s 410bf6c1 logcat`;
    exit;
}

输出:

aschirma@graphics9-lnx:~$ perl perl-fork-test.pl 
numKilled: 1
numKilled: 1
numKilled: 1
numKilled: 1
numKilled: 1
...

我期望的行为是我只看到numKilled: 1"一次，并且子进程(及其任何子进程)在大约 5 秒后被杀死.但我从实验中看到，无论是孩子还是他的孩子都没有被杀死.kill(SIGTERM, $childPid) 似乎什么都不做.

The behavior I expect is that I see "numKilled: 1" exactly once, and the child process (and any of its children) is killed after roughly 5 seconds. But I see from experiment that neither the child nor its children are getting killed. The kill(SIGTERM, $childPid) appears to do nothing.

我怎样才能真正杀死孩子?

How can I actually kill the child?

推荐答案

来自 perldoc 分支:

如果你分叉而不等待你的孩子，你会积累僵尸.在某些系统上，您可以通过将 $SIG{CHLD} 设置为忽略".

If you fork without ever waiting on your children, you will accumulate zombies. On some systems, you can avoid this by setting $SIG{CHLD} to "IGNORE" .

将 $SIG{CHLD} = 'IGNORE'; 添加到代码顶部时，我能够获得所需的行为.

I was able to get the desired behavior when adding $SIG{CHLD} = 'IGNORE'; to the top of your code.

[ben@imac ~]$ perl test.pl
numKilled: 1
[ben@imac ~]$ 

或者，在 kill 之后添加 waitpid($childPid, 0); 也能解决问题.

Alternatively, adding waitpid($childPid, 0); after kill did the trick as well.

这篇关于Perl fork and kill - kill(0, $pid) 总是返回 1，并且不能杀死孩子的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！