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You probably already know you can examine process status with ps, but most users never embrace the full power of ps. I’ve been talking about Linux concepts that wizards should know, but books often gloss over, and ps is at the top of the list. Let’s dig into processes using ps and some of its more useful options.
Some Basics
The ps utility lists some or all of your system’s current processes. By default– when you just run ps — you’ll only see processes owned by you (running under your UID). Whether ps shows some or all of the processes, for all users or only for you, depends on its configuration and on your system. For instance, ps on a shared Web host may prevent non-root users from seeing other users’ processes– even when using the “all” (-A) option.
The output of ps can also vary from system to system and kernel to kernel. Running ps on a multiprocessor system, for instance, can show which processor a job is running on. (To find out how many processors your system has and their characteristics, try running less /proc/cpuinfo. We’ll cover more of the /proc filesystem in a later column.)
To find out more about your ps, read its man page and compare its output on various systems. The GNU version understands three…
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