trap troubles

[Marty Wiedmeyer]

Hi,

I've discovered that trap doesn't work the way I thought it did.

I've used it to mop up tmp files with 
	trap 'rm -f /tmp/nifty.script*' 0 1 2 3 15
dependably for quite a while.

Now I want to do some real work with it :-).

One of my customers has a hardware PC "elevator" card in an Apollo.
Sometimes it dies unexpectedly with an exit code of 1. He wants to
run the PC-on-a-card from an sh script and give the user some options 
after the PCboard pukes, like
 
1) attempt to re-start the elevator
 
2) do nothing further if the elevator script/command exits 0.
 
3) if the elevator exits 1, either re-start, or ask to start
   up the software emulation (dpce).

However, I have discovered that executing a script which has a non-zero 
exit status and trap with commands to be executed upon that exit status 
(see below), results in the trapped commands _not_ being performed. Query 
of the shell immediately upon termination of the script with echo $? 
shows the correct exit status.

I have read TFM (in this case "The UNIX Shell Programming Language" 
Mannis/Meyer). It leads me to think it should be able to work
this way. Am I missing something?

Please email. I will try to keep up on this group, but the expire
time here is short.

Thanks!

   ------------------------Sample Script----------------------------
:
#
# Run this, then do 
# echo $? 
# at the shell!

trap 'echo "trap 2"' 2

ls

exit 2
-- 
Marty Wiedmeyer				INTERNET: mort at dhump.lakesys.com 
3473 N. Fratney St.  			BANG: uunet!marque!dhump!mort
Milwaukee, WI 563212			RING: (414) 963-2182