Read from stdin, stderr in Python

Question

I have two programs: p1 and p2. I run p1 | p2. I know how to read stdout from p1 in p2 stdin. How can I do the same with stderr.

Thanks, Nicolas

Answer 1

A pipe ( | ) in most (or all) shells takes the stdout of a command and passes it to the second command.

Taking the stderr from the first command can therefore only be done on the command line. In bash you'd do it this way:

p1 2>&1 | p2

This tells bash to forward stderr to stdout. Both are then piped to p2.

Alternatively you can make p1 print everything to stdout only.