'trap' compliency?

[Cristian Ionescu-Idbohrn]

On Thu, 24 Sep 2009, Denys Vlasenko wrote:

> I see. It's an EXIT trap firing when `trap` terminates...
>
> It's not easy to fix due to some peculiarities of ash.c code.
>
> Simplest but dirty solution would be to to unset EXIT trap
> in `trap`, but it will not show EXIT in `trap` output too.
> Which is bad, but "less bad" that what we have now.

I see you found a less dirty solution :)  Super, as what I'm chasing is
exactly EXIT traps.

I also see you mimic bash exactly, WRT output from $(trap).  I can't
really understand why bash is doing that unuseful thing as adding the SIG
in front of the signal name.  As I previously wrote:

On Wed, 23 Sep 2009, Cristian Ionescu-Idbohrn wrote:
>
> http://www.opengroup.org/onlinepubs/009695399/utilities/trap.html
> says:
>
> "The condition can be EXIT, 0 (equivalent to EXIT), or a signal specified
> using a symbolic name, without the SIG prefix"
>
> You've chosen to add the "SIG" in front of all the signal names.  May I
> ask why?
>
> bash's choice is to do something more inconsistent, IMO:
>
> 	trap -- 'echo Ho' EXIT
> 	trap -- 'echo Ho' SIGINT
> 	trap -- 'echo Ho' SIGTERM
>
> no "SIG" in front of EXIT.
> Thing is, if the quoted piece above is to be followed when doing:
>
> 	eval "$save_traps"
>
> then $(trap) should output:
>
> 	trap -- 'echo Ho' EXIT
> 	trap -- 'echo Ho' INT
> 	trap -- 'echo Ho' TERM
>
> Does that seem reasonable?

Yes, it does :)  Just skip the SIG thing.  bash does that itself if you
ask it to be POSIXLY_CORRECT.

,----
| If bash is invoked with the name sh, it tries to mimic the startup
| behavior of historical versions of sh as closely as possible, while
| conforming to the POSIX standard as well.
`----

Try something like this in the test scripts:

	set -o | egrep -q -w posix && set -o posix

and you'll see there's no SIG in the outout from $(trap).  And something
like this:

--- ash.c.orig	2009-09-26 17:43:45.000000000 +0200
+++ ash.c	2009-09-26 17:46:04.000000000 +0200
@@ -12267,9 +12267,8 @@ trapcmd(int argc UNUSED_PARAM, char **ar
 		for (signo = 0; signo < NSIG; signo++) {
 			char *tr = trap_ptr[signo];
 			if (tr) {
-				out1fmt("trap -- %s %s%s\n",
+				out1fmt("trap -- %s %s\n",
 						single_quote(tr),
-						(signo == 0 ? "" : "SIG"),
 						get_signame(signo));
 		/* trap_ptr != trap only if we are in special-cased `trap` code.
 		 * In this case, we will exit very soon, no need to free(). */

will save some bytes too :)


Cheers,

-- 
Cristian