View source for Ps (Unix)

{{Short description|Standard UNIX utility that displays the currently-running processes}}
{{multiple|
{{manual|date=April 2020}}
{{refimprove|date=October 2017}}
}}
{{Infobox software
| name                   = ps
| logo                   = 
| screenshot             = Ps command screenshot.png
| screenshot size        = 
| caption                = The {{code|ps}} command
| author                 = [[AT&T Bell Laboratories]]
| developer              = Various [[open-source software|open-source]] and [[commercial software|commercial]] developers
| released               = {{Start date and age|1973|2}}
| latest release version = 
| latest release date    = 
| programming language   = [[C (programming language)|C]]
| operating system       = [[Unix]], [[Unix-like]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], [[KolibriOS]], [[IBM i]]
| platform               = [[Cross-platform]]
| genre                  = [[Command (computing)|Command]]
| license                = Plan 9: [[MIT License]]
| website                = 
}}
In most [[Unix]] and [[Unix-like operating system]]s, the '''<code>ps</code>''' (''process status'') program displays the currently-running [[process (computing)|processes]].  The related Unix utility <code>[[top (software)|top]]</code> provides a real-time view of the running processes.

==Implementations==
[[KolibriOS]] includes an implementation of the {{code|ps}} [[command (computing)|command]].<ref>{{Cite web|url=http://wiki.kolibrios.org/wiki/Shell|title=Shell - KolibriOS wiki}}</ref> The {{Mono|ps}} command has also been ported to the [[IBM i]] operating system.<ref>{{cite web |title=IBM System i Version 7.2 Programming Qshell |language=en |author=IBM |website=[[IBM]] |author-link=IBM |url=https://www.ibm.com/support/knowledgecenter/ssw_ibm_i_74/rzahz/rzahzpdf.pdf?view=kc |access-date=2020-09-05 }}</ref> In [[Windows PowerShell]], <code>ps</code> is a predefined [[Alias (command)|command alias]] for the <code>Get-Process</code> cmdlet, which essentially serves the same purpose.

==Examples==
<syntaxhighlight lang="console">
# 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
</syntaxhighlight>

Users can [[Pipeline (Unix)|pipeline]] <code>ps</code> with other commands, such as [[Less (Unix)|less]] to view the process status output one page at a time:

<syntaxhighlight lang="console">
$ ps -A | less
</syntaxhighlight>

Users can also utilize the <code>ps</code> command in conjunction with the <code>[[grep]]</code>  command (see the <code>[[pgrep]]</code> and <code>[[pkill]]</code> commands) to find information about a single process, such as its id:<syntaxhighlight lang="console">
$ # Trying to find the PID of `firefox-bin` which is 2701
$ ps -A | grep firefox-bin
2701 ?        22:16:04 firefox-bin
</syntaxhighlight>

The use of <code>[[pgrep]]</code> simplifies the syntax and avoids potential race conditions:
<syntaxhighlight lang="console">
$ pgrep -l firefox-bin
2701 firefox-bin
</syntaxhighlight>

To see every process running as root in user format:
<syntaxhighlight lang="console">
# 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 --
</syntaxhighlight>

==Header line==
{| class="wikitable"
|-
! Column Header !! Contents
|-
| %CPU || How much of the CPU the process is using
|-
| %MEM || How much memory the process is using
|-
| ADDR || Memory address of the process
|-
| C or CP || CPU usage and scheduling information
|-
| COMMAND* || Name of the process, including arguments, if any
|-
| NI ||[[Nice (Unix)|nice]] value
|-
| F || Flags
|-
| PID || Process ID number
|-
| PPID || ID number of the process's parent process
|-
| PRI || Priority of the process
|-
| RSS || [[Resident set size]]
|-
| S or STAT || Process status code
|-
| START or STIME || Time when the process started
|-
| VSZ || Virtual memory usage
|-
| TIME || The amount of CPU time used by the process
|-
| TT or TTY || Terminal associated with the process
|-
| UID or USER || Username of the process's owner
|-
| WCHAN || Memory address of the event the process is waiting for
|}
<nowiki>* = Often abbreviated</nowiki>

==Options==
<code>ps</code> has many options. On [[operating system]]s that support the [[Single UNIX Specification|SUS]] and [[POSIX]] standards, <code>ps</code> commonly runs with the options '''-ef''', where "-e" selects '''e'''very process and "-f" chooses the "'''f'''ull" output format. Another common option on these systems is '''-l''', which specifies the "'''l'''ong" 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 variable]]s.) On such systems, <code>ps</code> commonly runs with the non-standard options '''aux''', where "a" lists all processes on a [[Computer terminal|terminal]], including those of other users, "x" lists all processes without [[controlling terminal]]s 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==
* [[Task manager]]
* [[kill (command)]]
* [[List of Unix commands]]
* [[nmon]] – a system monitor tool for AIX and Linux operating systems
* [[pstree (Unix)]]
* [[lsof]]

==References==
{{Reflist}}

==Further reading==
*{{Cite book|author-last=McElhearn|author-first=Kirk|title=The Mac OS X Command Line: Unix Under the Hood|date=2006|publisher=[[John Wiley & Sons]]|isbn=978-0470113851}}
*{{Cite book|last1=Shotts (Jr)|first1=William E.|title=The Linux Command Line: A Complete Introduction|date=2012|publisher=No Starch Press|isbn=9781593273897|pages=96–98|url=https://books.google.com/books?id=OCFKdl3wEDIC|access-date=16 October 2017|language=en}}

==External links==
{{Wikibooks|Guide to Unix|Commands}}
* {{man|cu|ps|SUS}}
* {{man|1|ps|Plan 9}}
* {{man|1|ps|Inferno}}
* [http://www.cyberciti.biz/faq/show-all-running-processes-in-linux/ Show all running processes in Linux using ps command]
* [http://kb.iu.edu/data/afnv.html In Unix, what do the output fields of the ps command mean?]

{{Unix commands}}
{{Plan 9 commands}}

{{lowercase}}
[[Category:Unix SUS2008 utilities]]
[[Category:Unix process- and task-management-related software]]
[[Category:Plan 9 commands]]
[[Category:Inferno (operating system) commands]]
[[Category:IBM i Qshell commands]]