[BUILTIN] Make trap signal name/number errors non-fatal.

On Wed, Feb 24, 2010 at 10:23:34AM +0000, Peter Kjellerstedt wrote:
>
> there seems to be a problem  with the trap implementation in dash
> (tested with 0.5.4 and 0.5.5.1). If I specify a signal which is not
> supported, the shell unconditionally aborts. E.g., I had expected
> the following to print foo (like bash and zsh do):
>
> # dash -c 'trap "echo trap executed" UNKNOWNSIGNAL || echo "foo"'
> trap: 1: UNKNOWNSIGNAL: bad trap
>
> This means I cannot write a construct like the following to take
> advantage of the ERR signal which is present in some shells:
>
> trap "echo ERR trap executed" ERR 2>/dev/null || :
>
> I also checked the POSIX documentation, and quoting from
> http://www.opengroup.org/onlinepubs/009695399/utilities/trap.html
> (exit status): "For both interactive and non-interactive shells,
> invalid signal names [XSI] [Option Start] or numbers [Option End]
> shall not be considered a syntax error and do not cause the shell
> to abort."

This patch replaces sh_error with a outfmt + return 1 in trapcmd
so that these errors are no longer fatal.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/trap.c b/src/trap.c
index 16703b3..3f93c46 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -117,8 +117,10 @@ trapcmd(int argc, char **argv)
 	else
 		action = *ap++;
 	while (*ap) {
-		if ((signo = decode_signal(*ap, 0)) < 0)
-			sh_error("%s: bad trap", *ap);
+		if ((signo = decode_signal(*ap, 0)) < 0) {
+			outfmt(out2, "trap: %s: bad trap\n", *ap);
+			return 1;
+		}
 		INTOFF;
 		if (action) {
 			if (action[0] == '-' && action[1] == '\0')