Method: Kernel#fork

Defined in:

process.c

#fork { ... } ⇒ Fixnum^? #fork { ... } ⇒ Fixnum^?

Creates a subprocess. If a block is specified, that block is run in the subprocess, and the subprocess terminates with a status of zero. Otherwise, the fork call returns twice, once in the parent, returning the process ID of the child, and once in the child, returning nil. The child process can exit using Kernel.exit! to avoid running any at_exit functions. The parent process should use Process.wait to collect the termination statuses of its children or use Process.detach to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.

The thread calling fork is the only thread in the created child process. fork doesn’t copy other threads.

If fork is not usable, Process.respond_to?(:fork) returns false.

Note that fork(2) is not available on some platforms like Windows and NetBSD 4. Therefore you should use spawn() instead of fork().

Overloads:

• #fork { ... } ⇒ Fixnum^?

  Yields:

  Returns:

  • (Fixnum, nil)
• #fork { ... } ⇒ Fixnum^?

  Yields:

  Returns:

  • (Fixnum, nil)

# File 'process.c', line 3698

static VALUE
rb_f_fork(VALUE obj)
{
    rb_pid_t pid;

    switch (pid = rb_fork_ruby(NULL)) {
      case 0:
	rb_thread_atfork();
	if (rb_block_given_p()) {
	    int status;

	    rb_protect(rb_yield, Qundef, &status);
	    ruby_stop(status);
	}
	return Qnil;

      case -1:
	rb_sys_fail("fork(2)");
	return Qnil;

      default:
	return PIDT2NUM(pid);
    }
}