[Splashy-devel] Bug#473112: Bug#473112: splashy: breaks udev - log_daemon_msg does not play well with -e switch from udev script

[Alban Browaeys]

On ven, 2008-03-28 at 15:58 +0100, John Hughes wrote:

> So it would be simpler to get rid of the "pidof splashy" call:
> 
>     splashy_update "scroll $1: $2" 2>/dev/null || true



> But doing some tests it looks like most (all?) shells don't treat a
> command that contains && as an error:
> 
>     $ cat zztest
>     set -e
>     pidof noprog && echo "noprog running"
>     echo no error
>     $ sh -x zztest
>     + set -e
>     + pidof noprog
>     + echo no error
>     no error
>       
> 
> Maybe there is some other problem?
> 
> Maybe it's splashy_update that's failing?


man "set" :
-e     When this option is on, if a simple command fails for any of the
reasons  listed  in  Consequences  of Shell Errors or returns an
exit status value >0, and is not part of the compound list  fol‐
lowing  a  while,  until, or if keyword, and is not a part of an
AND or OR list, and is not a pipeline preceded by the ! reserved
word, then the shell shall immediately exit.

http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_08_01

So the behaviour for AND or OR list is not obvious for me ... 
for example :
set -e 
false && true
echo "no error"
returns : "no error".
by the way :
false && false also returns "no error" so what kills the script is not
the exit status in a list ...



So basically I agree && does not trigger an error . What I found out is
that inside a function the behaviour changes :

set -e
a() {
false && true
}
a;
echo "no error"

fails while :
set -e
a() {
false && true || true
}
a;
echo "no error"
succeed.

So my patch seems needed to get things working as lsb-base-logging.sh
make the list of calls in functions.
Best regards
Alban