Verboser output of child in case of invalid/unknown command

We are currently validating various libs for a simple process handling in C++ (came from Boost.Process...) and are quite excited about subprocess.h

However, when doing some basic tests we might have found a part of the lib, which could be improved to ease troubleshooting for the user/developer.
E. g. when somebody gives an invalid command (e.g. lss) no further information is given. In contrast, other libs give some hint in the form of execv's perror message or a dedicated error code. In case you are interested i appended you our patch file. With this update it is possible to check the child's stdout/stderr for the error message or simply provide it to the user.

If you have any further questions please feel free to ask.

subprocess.perror.patch.txt

Updated the patch. Maybe the best approach would be to forward a dedicated error code to the parent?

subprocess.perror.patch.txt

[sheredom]

Hey there! Any chance you've got a dumb test case with the output you get with this patch? I just want to understand what is being reported back to the user with it, so I can guage how to make this work nicer.