ps - Additional Information, Notes, and Process State Codes

The section argument can be one of simple, list, output, threads, misc, or all. The argument can be shortened to one of the underlined letters as in: s|l|o|t|m|a. --info Print debugging info. L List all format specifiers. V Print the procps‐ng version. -V Print the procps‐ng version. --version Print the procps‐ng version. NOTES This ps works by reading the virtual files in /proc. This ps does not need to be setuid kmem or have any privileges to run. Do not give this ps any special permissions. CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process. This is not ideal, and it does not conform to the standards that ps otherwise conforms to. CPU usage is unlikely to add up to exactly 100%. The SIZE and RSS fields don’t count some parts of a process including the page tables, kernel stack, struct thread_info, and struct task_struct. This is usually at least 20 KiB of memory that is always resident. SIZE is the virtual size of the process (code+data+stack). Processes marked <defunct> are dead processes (so-called "zombies") that remain because their parent has not destroyed them properly. These processes will be destroyed by init(8) if the parent process exits. If the length of the username is greater than the width of the display column, the username will be truncated. See the -o and -O formatting options to customize length. Commands options such as ps -aux are not recommended as it is a confusion of two different standards. According to the POSIX and UNIX standards, the above command asks to display all processes with a TTY (generally the commands users are running) plus all processes owned by a user named x. If that user doesn’t exist, then ps will assume you really meant ps aux. PROCESS FLAGS The sum of these values is displayed in the "F" column, which is provided by the flags output specifier: 1 forked but didn’t exec 4 used super-user privileges PROCESS STATE CODES Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process: D uninterruptible sleep (usually IO) I Idle kernel thread R running or runnable (on run queue) S interruptible sleep (waiting for an event to complete) T stopped by job control signal t stopped by debugger during the tracing W paging (not valid since the 2.6.xx kernel) X dead (should never be seen) Z defunct ("zombie") process, terminated but not reaped by its parent For BSD formats and when the stat keyword is used, additional characters may be displayed: < high-priority (not nice to other users) N low-priority (nice to other users) L has pages locked into memory (for real-time and custom IO) s is a session leader l is multi‐threaded (using CLONE_THREAD, like NPTL pthreads do) + is in the foreground process group OBSOLETE SORT KEYS These keys are used by the BSD O option (when it is used for sorting). The GNU --sort option doesn’t use these keys, but the specifiers described below in the STANDARD FORMAT SPECIFIERS section. Note that the values used in sorting are the internal values ps uses and not the "cooked" values used in some of the output format fields (e.g. sorting

This section provides additional details about the `ps` command. It explains how to get debugging information, list format specifiers, and display the version. It includes notes on how `ps` works by reading virtual files and handling CPU usage calculations. It describes what the SIZE and RSS fields include. It also explains defunct processes, username truncation, and recommends against using commands like `ps -aux` due to potential confusion. Finally, it lists process flags, state codes, and obsolete sort keys used by the BSD O option.