[launchd-dev] Preventing killing of child processes?

[Sidney San Martín]

That did help — and as it turns out, my problem wasn't launchd, but a
missed SIGPIPE at the same time. I should have debugged it out more
before posting to the list.

Thanks, Dave.

On Fri, Oct 9, 2009 at 7:50 PM, Dave Keck <davekeck at gmail.com> wrote:
>> That doesn't seem to be doing it. The child process still exits as
>> soon as it unloads the parent job from launchd.
>
> Hmm, I just did a controlled test, and it certainly does the trick for
> me on 10.5.8. Here's what I did:
>
> ===== parent_process.c
>
> #include <stdio.h>
> #include <unistd.h>
>
> int main(int argc, const char *argv[])
> {
>    if (!fork())
>    {
>        execl("/child_process", "/child_process");
>        _exit(0);
>    }
>    sleep(10);
>    return 0;
> }
>
> ===== child_process.c
>
> #include <stdio.h>
> #include <unistd.h>
>
> int main(int argc, const char *argv[])
> {
>    setpgrp();
>    sleep(60);
>    return 0;
> }
>
> ===== com.parent.parent_process.plist
>
> <?xml version="1.0" encoding="UTF-8"?>
> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
> "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
> <plist version="1.0">
> <dict>
> <key>Label</key>
> <string>com.parent.parent_process</string>
> <key>ProgramArguments</key>
> <array>
> <string>/parent_process</string>
> </array>
> <key>RunAtLoad</key>
> <true/>
> </dict>
> </plist>
>
> =====
>
> Compile parent_process.c and child_process.c, and put them and the
> plist in your drive's root directory. Then:
>
>    launchctl load /com.parent.parent_process.plist
>
> You'll notice that the parent exits after 10 seconds, while the child
> stays alive for a full minute. Likewise, if you unload the parent
> early, the child still stays alive past the parent's death. Without
> setpgrp(), the child dies with the parent. Does that help?
>