Exit when one process in pipe fails

Question

The goal was to make a simple unintrusive wrapper that traces stdin and stdout to stderr:

#!/bin/bash

tee /dev/stderr | ./script.sh | tee /dev/stderr

exit          


        

Answer 1

The main issue at hand here is clearly the pipe. In bash, when executing a command of the form

command1 | command2

and command2 dies or terminates, the pipe which receives the output (/dev/stdout) from command1 becomes broken. The broken pipe, however, does not terminate command1. This will only happen when it tries to write to the broken pipe, upon which it will exit with sigpipe. A simple demonstration of this can be seen in this question.

If you want to avoid this problem, you should make use of process substitution in combination with input redirection. This way, you avoid pipes. The above pipeline is then written as:

command2 < <(command1)

In the case of the OP, this would become:

./script.sh < <(tee /dev/stderr) | tee /dev/stderr

which can also be written as:

./script.sh < <(tee /dev/stderr) > >(tee /dev/stderr)