Makefiles and failing commands

README.md

How does a Makefile react to failing commands?

There are three scripts:

• good.sh exits successfully
• maybe.sh contains a failing command, but its last command succeeds, so the whole script exits successfully
• bad.sh adds set -e to maybe.sh, causing the script to fail after the first failing command

The Makefile targets of good, bad, and ugly depend on those scripts. Note that good and ugly succeed while bad fails.

The targets of good-dep, bad-dep, and ugly-dep depend on the above targets. Again, good-dep and ugly-dep succeed, and the additional rules run. bad-dep stops after running bad, since it failed.

The good-bad and bad-good targets run the good.sh and bad.sh scripts in opposite orders. Both stop after running the bad script, and both fail.

The good-bad-dep and bad-good-dep depend on both good and bad, in opposite orders. The dependent commands are run in the order listed, and execution ends after running bad. Both fail, and neither runs its own code.

bad.sh

#!/bin/bash

set -e
echo "Bad"
false
true

good.sh

#!/bin/bash

set -e
echo "Good"
true

Makefile

.PHONY: good bad ugly good-bad bad-good good-dep bad-dep ugly-dep good-bad-dep bad-good-dep

good:
	./good.sh

bad:
	./bad.sh

ugly:
	./ugly.sh

good-bad:
	./good.sh
	./bad.sh

bad-good:
	./bad.sh
	./good.sh

good-dep: good
	echo "Good parent"

bad-dep: bad
	echo "Bad parent"

ugly-dep: ugly
	echo "Ugly parent"

good-bad-dep: good bad
	echo "Good bad"

bad-good-dep: bad good
	echo "Bad good"

ugly.sh

#!/bin/bash

echo "Ugly"
false
true