Say you have a shell script, and you need it to be bulletproof.
As you write it, you throw in error checking all over the place.
But say you have a function that needs to return a boolean result in some
way - call the function "bool_foo" for the sake of discussion. Further
assume that bool_foo will sometimes fail to return a result, and it's
defined with:
function bool_foo
(
xyz
)
...and not function bool_foo
{
xyz
}
...so that bool_foo's variables don't mess with those of other functions,
but also making it so it cannot just exit 1 to terminate the program
directly.
How would you go about making bool_foo return a boolean result -and- be
able to return a fatal?
Do you make bool_foo echo "True" or "False" and use the exit status to
reflect success/failure?
Or do you make 0 mean True, 1 mean False, and anything else mean fatal in
$?? And if so, how do you go about differentiating these three things -
do you use nested if's or a case? And what if you have set -e in effect?
I'm sure I can come up with A way of handling this, but what have you
found works well in practice?
I suspect I'm going to end up rewriting my bool_foo functions to echo
True or False, and then use their exit status to indicated success or
failure. So instead of:
if bool_foo
then
: true
else
: false
fi
...it seems I'll end up with this mess scattered all over (with set -eu
in effect, among other things) :
case "$(shell_init; bool_foo)" in
True)
: true
;;
False)
: true
;;
*)
echo "$0: Unrecognized output from bool_foo" 1>&2
exit 1
;;
esac
I guess what I'm saying is "I miss having an exception mechanism" :)
Followups directed to comp.unix.shell.
