CODEWITHSUNDEEP
perlsystemforkparallel-processing
numegil
numegil

Reputation: 1926

Perl system() command failing after fork

I have a perl script which calls fork() a few times to create 4 child processes. The parent process then uses waitpid() to wait for all of the children to finish.

The problem occurs when I try to call system() from within the child processes (I'm using it to create directories). Even something as simple as system("dir") fails (yes, I'm on Windows).

By "fails", I mean that one of the child threads goes past it no problem, but the other child processes so far as I can tell simply cease to exist.

trace INFO, "Thread $thread_id still alive at 2.62";
system("dir");
trace INFO, "Thread $thread_id still alive at 2.65";

I get messages such as "Thread 3 still alive at 2.62", but only 1 of the child threads ever gets to 2.65.

At the bottom of the log, I can see "Command exited with non-zero status 127", which I think may have something to do with it.

I've considered using some sort of a mutex lock to make sure that only 1 processes at a time goes through the system calls, but how can I do that with fork()? Also, this problem doesn't really make any sense in the first place, why would several independent processes have trouble doing system("dir") at the same time?

Upvotes: 1

Views: 622

Answers (1)

Ivan Nevostruev
Ivan Nevostruev

Reputation: 28723

The problem here is that fork() is emulated under windows using threads. So there is no real processes created.

If you are only use system call to create folders, then you'd better use perl function mkdir or File::Path's make_path instead.

Upvotes: 2

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