Shell Library Design

Status Return

Report Failure

Library functions should return a status that callers can branch on. The caller can then turn the status into a clear outcome message.

Program

Play the script to choose the task mode and see how the caller handles the return status.

library_status_return.sh 
#!/usr/bin/env bash

mode=
run_task() {
    if [[ "$mode" == "apply" ]]; then
        return 0
    fi
    return 2
}
if run_task; then
    outcome="ok"
else
    outcome="skip:$?"
fi
echo "$mode:$outcome"

#!/usr/bin/env bash

mode=
run_task() {
    if [[ "$mode" == "apply" ]]; then
        return 0
    fi
    return 2
}
if run_task; then
    outcome="ok"
else
    outcome="skip:$?"
fi
echo "$mode:$outcome"
return status A function returns a numeric status that the caller can test.
caller branch The caller decides how to handle success or failure.
status message Turning a numeric status into a message makes failures easier to inspect.