Re: How to trap EXIT like in bash

[Philippe Troin <phil@fifi.org>]

On Sat, 2015-04-04 at 19:43 +0200, Thorsten Kampe wrote:
> * Philippe Troin (Sat, 04 Apr 2015 10:08:34 -0700)
> > 
> > On Sat, 2015-04-04 at 17:20 +0200, Thorsten Kampe wrote:
> > > in Bash `trap "echo trapped" EXIT` will trigger when the script 
> > > terminates normally and on SIGINT, SIGTERM, and SIGHUP.
> > > 
> > > In Zsh, `trap "echo trapped" EXIT` triggers only on normal exit, but 
> > > `trap "echo trapped" EXIT INT` will actually trigger twice on Ctrl-C.
> > > 
> > > How can I trap normal exit, Ctrl-C, SIGTERM and SIGHUP so trap 
> > > function will only run once?
> > 
> > I use this:
> > 
> > trap "echo trapped; exit 0" EXIT INT
> 
> I just tested it: Zsh is trapped once but bash twice on INT.
> 
> This works:
> ```
> if [[ $shell = bash ]]
> then
>     trap "echo trapped" EXIT
> 
> elif [[ $shell = zsh ]]
> then
>     trap "echo trapped; exit" INT
> fi
> ```

Yes, you're right.  For some reason it did work for me but I can't
reproduce it.  This would work everywhere:

  trap "echo trapped; trap - EXIT; exit 0" EXIT INT

With bash:

        % bash --version
        GNU bash, version 4.2.53(1)-release (x86_64-redhat-linux-gnu)
        Copyright (C) 2011 Free Software Foundation, Inc.
        License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
        
        This is free software; you are free to change and redistribute it.
        There is NO WARRANTY, to the extent permitted by law.
        % for i in INT TERM HUP QUIT; do bash -c 'trap "echo trapped \$?; trap - EXIT; exit 0" EXIT INT TERM HUP QUIT; sleep 5' & sleep 1; kill -$i -$!; wait; done
        [2] 28903
        trapped 130
        [2]  + done       bash -c 
        [1] 28906
        Terminated
        trapped 143
        [1]  + done       bash -c 
        [1] 28909
        Hangup
        trapped 129
        [1]  + done       bash -c 
        [1] 28912
        Quit
        trapped 131
        [1]  + done       bash -c 
        % 
        
With zsh:

        % zsh --version
        zsh 5.0.7 (x86_64-redhat-linux-gnu)
        % for i in INT TERM HUP QUIT; do zsh -fc 'trap "echo trapped \$?; trap - EXIT; exit 0" EXIT INT TERM HUP QUIT; sleep 5' & sleep 1; kill -$i -$!; wait; done
        [2] 28936
        trapped 130
        [2]  + done       zsh -fc 
        [1] 28940
        trapped 143
        [1]  + done       zsh -fc 
        [1] 28943
        trapped 129
        [1]  + done       zsh -fc 
        [1] 28947
        trapped 131
        [1]  + done       zsh -fc 
        % 

> BUT: it does not work when I extend the signals to
> ```
> elif [[ $shell = zsh ]]
> then
>     trap "echo trapped; exit" INT HUP TERM
> fi
> ```
> 
> Then Zsh does actually ignore the kill (TERM) signal.

That's not the behavior I'm seeing above.

Phil.