Check exit code of a program called in a while loop
In addition to the well-known while
loop, POSIX provides an until
loop that eliminates the need to negate the exit status of my_command
.
# To demonstrate
my_command () { read number; return $number; }
until my_command; do
if [ $? -eq 5 ]; then
echo "Error was 5"
else
echo "Error was not 5"
fi
# potentially, other code follows...
done
If true
command hurt your sensibility, you could write:
while my_command ; ret=$? ; [ $ret -ne 0 ];do
echo do something with $ret
done
This could be simplified:
while my_command ; ((ret=$?)) ;do
echo do something with $ret
done
But if you don't need ResultCode, you could simply:
while my_command ; [ $? -ne 0 ];do
echo Loop on my_command
done
or
while my_command ; (($?)) ;do
echo Loop on my_command
done
And maybe, why not?
while ! my_command ;do
echo Loop on my_command
done
But from there you could better use until
as chepner suggest
You can get the status of a negated command from the PIPESTATUS
built-in variable:
while ! my_command ; do
some_code_dependent_on_exit_code "${PIPESTATUS[0]}"
done
chepner's solution is better in this case, but PIPESTATUS
is sometimes useful for similar problems.