ps can not recognize the user defined format expressions. such as ps -o %p
does seem to be very broken.
The PS also doesn't match the MAN pages, which give examples which don't work. I have many scripts which have broken. Should I attempt to fix it and submit a patch, or is someone at RedHat already working on it?
If you want to work on this code, please read ps/HACKING which the author so kindly provided. You broke the retry logic when you blindly added the code to complain about unknown format options, and you obviously did not run examples from the man page.
Works for me at least in 2.0.7-23