Antw: [EXT] Re: declare XXX=$(false);echo $?

[Ulrich Windl]

>>> Martin D Kealey <martin@kurahaupo.gen.nz> schrieb am 03.12.2022 um 02:26 in
Nachricht
<CAN_U6MVDGDapEmqKqaqE5A=Hte7V9SuQQt7yBsj2kcLe+ObyJg@mail.gmail.com>:

...

> Found in the real code (intended to trigger a bug):
>>     declare ERRORS=0 ARGS=$(getopt -o "$S_OPTS" -l "$L_OPTS" -n "$0" --
>> "$@")
>>
>     if [ $? -ne 0 ]; then
>>         usage
>>     fi
>>
> 
> That is a well-known anti-pattern that should be avoided.
> 
> Some working equivalents would be:
> ```
>     declare ARGS=$( getopt -o "$S_OPTS" -l "$L_OPTS" -n "$0" -- "$@" )
> ERRORS=$?
>     (( ERRORS == 0 )) || usage
> ```
> or:
> ```
>     declare ARGS ERRORS=0
>     ARGS=$( getopt -o "$S_OPTS" -l "$L_OPTS" -n "$0" -- "$@" ) ||
>         usage
> ```
> 
> -Martin
> 
> (PS: "Working" would be questionable, since putting `getopt` in a subshell
> prevents it from updating "$@"; and `test $? = 0` and its variants are
> pointless clutter.)

Well, the code proved to work, and the pattern was found in 
/usr/share/getopt/getopt-parse.bash (of BASH 4.3):

...
# Note that we use "$@" to let each command-line parameter expand to a
# separate word. The quotes around "$@" are essential!
# We need TEMP as the 'eval set --' would nuke the return value of getopt.
TEMP=$(getopt -o 'ab:c::' --long 'a-long,b-long:,c-long::' -n 'example.bash' -- 
"$@")

if [ $? -ne 0 ]; then
        echo 'Terminating...' >&2
        exit 1
fi
...