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ps (Unix)

Standard UNIX utility that displays the currently-running processes

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ps

The ps command
Original author(s)	AT&T Bell Laboratories
Developer(s)	Various open-source and commercial developers
Initial release	February 1973; 51 years ago (1973-02)
Written in	C
Operating system	Unix, Unix-like, Plan 9, Inferno, KolibriOS, IBM i
Platform	Cross-platform
Type	Command
License	Plan 9: MIT License

In most Unix and Unix-like operating systems, the ps (process status) program displays the currently-running processes. The related Unix utility top provides a real-time view of the running processes.

Implementations[edit]

KolibriOS includes an implementation of the ps command.^[1] The ps command has also been ported to the IBM i operating system.^[2]InWindows PowerShell, ps is a predefined command alias for the Get-Process cmdlet, which essentially serves the same purpose.

Examples[edit]

# ps  PID TTY          TIME CMD
 7431 pts/0    00:00:00 su
 7434 pts/0    00:00:00 bash
18585 pts/0    00:00:00 ps

Users can pipeline ps with other commands, such as less to view the process status output one page at a time:

$ ps -A | less

Users can also utilize the ps command in conjunction with the grep command (see the pgrep and pkill commands) to find information about a single process, such as its id:

$ # Trying to find the PID of `firefox-bin` which is 2701
$ ps -A | grep firefox-bin
2701 ?        22:16:04 firefox-bin

The use of pgrep simplifies the syntax and avoids potential race conditions:

$ pgrep -l firefox-bin
2701 firefox-bin

To see every process running as root in user format:

# ps -U root -u
USER   PID  %CPU %MEM    VSZ   RSS TT  STAT STARTED        TIME COMMAND
root     1   0.0  0.0   9436   128  -  ILs  Sun00AM     0:00.12 /sbin/init --

Header line[edit]

* = Often abbreviated

Options[edit]

ps has many options. On operating systems that support the SUS and POSIX standards, ps commonly runs with the options -ef, where "-e" selects every process and "-f" chooses the "full" output format. Another common option on these systems is -l, which specifies the "long" output format.

Most systems derived from BSD fail to accept the SUS and POSIX standard options because of historical conflicts. (For example, the "e" or "-e" option will display environment variables.) On such systems, ps commonly runs with the non-standard options aux, where "a" lists all processes on a terminal, including those of other users, "x" lists all processes without controlling terminals and "u" adds a column for the controlling user for each process. For maximum compatibility, there is no "-" in front of the "aux". "ps auxww" provides complete information about the process, including all parameters.

See also[edit]

• Task manager
• kill (command)
• List of Unix commands
• nmon – a system monitor tool for AIX and Linux operating systems
• pstree (Unix)
• lsof

References[edit]

Further reading[edit]

• McElhearn, Kirk (2006). The Mac OS X Command Line: Unix Under the Hood. John Wiley & Sons. ISBN 978-0470113851.
• Shotts (Jr), William E. (2012). The Linux Command Line: A Complete Introduction. No Starch Press. pp. 96–98. ISBN 9781593273897. Retrieved 16 October 2017.

External links[edit]

The Wikibook Guide to Unix has a page on the topic of: Commands

• ps – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
• ps(1) – Plan 9 Programmer's Manual, Volume 1
• ps(1) – Inferno General commands Manual
• Show all running processes in Linux using ps command
• In Unix, what do the output fields of the ps command mean?