Return value for PTY.spawn

ruby-talk
1

Hi rubyists :wink:

Is there a way to retrieve the return value of a process which was
started by PTY.spawn?

I could not find any documentation about the pty class.

Thank you in advance.

···

–
Laurent

2

Laurent Sansonetti wrote:

Hi rubyists :wink:

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 :wink:

···

–
Laurent

3

Hi,

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:

PTY::ChildExited has the accessor “status” already.

begin
PTY.spawn(…) { … }
rescue PTY::ChildExited => e
e = e.status
pid = e.pid
val = e.status

···

At Wed, 14 May 2003 23:08:28 +0900, Laurent Sansonetti wrote:

end

–
Nobu Nakada

4

Sorry, I was using an old version of pty.

I just retrieved the lastest sources from CVS, and everything is working
fine :wink:

Apologies for this issue…

···

nobu.nokada@softhome.net wrote:

PTY::ChildExited has the accessor “status” already.

–
Laurent