When I try to compute the diff between two text files:
results.txt: file1.txt file2.txt
diff $(word 1,$^) $(word 2,$^) > $@
I get this weird (?) error:
$ make
diff file1.txt file2.txt > results.txt
makefile:2: recipe for target 'results.txt' failed
make: *** [results.txt] Error 1
What's wrong with my makefile?
The issue is that diff typically has a non-zero exit code if the files differ. This will cause make to infer the command failed. The easy fix would be to tell make to ignore the exit code...
results.txt: file1.txt file2.txt
-diff $(word 1,$^) $(word 2,$^) > $@
Edit: If the aim is to get rid of the diagnostic message entirely then you could just use something like...
results.txt: file1.txt file2.txt
diff $(word 1,$^) $(word 2,$^) > $@ || exit 0