Friday, January 27, 2023

Tip of the Trade: ps Options

Admins use ps all the time to look at processes running on a
system. But do you make the best use of the
multitude of options this very useful tool has, or do you stick to a tiny, tested handful? Here are some ps options to check out that you may not have encountered before.

  • ps r: Shows only running processes.
  • ps f: Shows children descended from their parents in an
    ASCII art tree. I find this very useful when looking at problem
    processes. Use with the S option to see CPU information from
    children summed up with parents.
  • ps e: Shows the command environment for each process. This
    is useful in a situation where a program works for one user but not for
    another, or on one machine but not on another.
  • ps -t pts/3: Shows processes associated with the specified
    tty. I’ve found this useful when trying to work out who’s doing what on a
    remote machine, and for how long.
  • ps u: Generates much more readable and human friendly
    output. Check the manpage for help with output column headings.

Options can be combined, but note that there are three types of option: a
single dash, a double dash or no dash at all. u is different
from -u. When combining options, the different option types must
be grouped separately (e.g., ps Sf -u jkemp.)

There are many more options that I haven’t space to discuss here — go check
out the manpage, and get yet more improved and exciting process info (try X or s)!

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