From: Laurent Sansonetti <laurent@...>
Date: 2003-05-14T23:08:28+09:00
Subject: [PATCH] Re: return value for PTY.spawn

Laurent Sansonetti wrote:

> Hi rubyists ;-)
> 
> Is there a way to retrieve the return value of a process which was
> started by PTY.spawn?
> 

Finally, after some tests, I looked the code.

Here is a patch for pty.c, which will include the exit value of the 
spawned process in the ChildExited exception:

<<------------------------------------------------------------------
--- pty.c.old   Wed May 14 16:41:29 2003
+++ pty.c       Wed May 14 16:47:21 2003
@@ -138,12 +138,13 @@
      struct pty_info *info;
  {
      extern VALUE rb_last_status;
-    int cpid, status;
+    int cpid, status, retval;
      char buf[1024];
      VALUE exc, st;
      char *state = "changed";

      cpid = rb_waitpid(info->child_pid, &status, WUNTRACED);
+    retval = WEXITSTATUS(status);
      st = rb_last_status;

      if (cpid == 0 || cpid == -1)
@@ -166,7 +167,7 @@
         state = "exit";
      }

-    snprintf(buf, sizeof(buf), "pty - %s: %d", state, cpid);
+    snprintf(buf, sizeof(buf), "pty - %s: %d (%d)", state, cpid, retval);
      exc = rb_exc_new2(eChildExited, buf);
      rb_iv_set(exc, "status", st);
      rb_funcall(info->thread, rb_intern("raise"), 1, exc);
------------------------------------------------------------------>>

And an IRB session working with the patched pty.so:

<<------------------------------------------------------------------
pinux@natalie /[...]/ruby-1.8.0/ext/pty> irb18 --simple-prompt
 >> require 'pty'
=> true
 >> PTY.spawn("uname") { |r, w, pid| puts r.readlines }
FreeBSD
PTY::ChildExited: pty - exit: 26219 (0)
         from (irb):3:in `spawn'
         from (irb):3
 >> PTY.spawn("ls /does_not_exist") { |r, w, pid| puts r.readlines }
ls: /does_not_exist: No such file or directory
PTY::ChildExited: pty - exit: 26239 (1)
         from (irb):4:in `spawn'
         from (irb):4
 >> PTY.spawn("ls") { |r, w, pid| puts r.readlines }
MANIFEST                README.expect           depend 
lib                     pty.c.old               script.rb
Makefile                README.expect.ja        expect_sample.rb 
mkmf.log                pty.o                   shl.rb
README                  README.ja               extconf.rb 
pty.c                   pty.so
PTY::ChildExited: pty - exit: 26240 (0)
         from (irb):5:in `spawn'
         from (irb):5
 >>
------------------------------------------------------------------>>

I know this is not very 'clean' to add information in the exception.
Maybe we should include these information in the class itself, and 
create some accessor methods, so we can write:

	begin
		PTY.spawn(...) { ... }
	rescue => e
		raise unless e.is_a?(PTY::ChildExited)
		pid = e.pid
		val = e.exit_val
	end

BTW, please excuse me for my bad English ;-)

--
Laurent