Shell – Chaining pipe | with &&

If you're not worried about the timing of data passing from foo to bar, and you're okay with a tempfile which will need to be handled in your clean target, then simply:

rcheck:
        foo | tee sometempfile
        -bar < sometempfile >/dev/null 2>/dev/null

If on the other hand you care a lot about timing then you could make bar repeat its input to stdout and try something like:

rcheck:
        -(foo; echo $$? > sometempfile) | bar
        exit $(cat sometempfile)

I'm sure there'll be cleaner ways, but the above came to mind. (Note, both are untested)

Use grep like this:

$ grep -v -x -F -f forbidden.txt input.txt

That long list of options to grep means

• -v Invert the sense of the match, i.e. look for lines not matching.
• -x When matching a pattern, require that the pattern matches the whole line, i.e. not just anywhere on the line.
• -F When matching a pattern, treat it as a fixed string, i.e. not as a regular expression.
• -f Read patterns from the given file (forbidden.txt).

Then pipe that to sort or whatever you want to do with it.