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PS(1P)			   POSIX Programmer's Manual			PS(1P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       ps — report process status

SYNOPSIS
       ps [−aA] [−defl] [−g grouplist] [−G grouplist]
	   [−n namelist] [−o format]... [−p proclist] [−t termlist]
	   [−u userlist] [−U userlist]

DESCRIPTION
       The ps utility shall write information about processes, subject to hav‐
       ing appropriate privileges to obtain information about those processes.

       By  default, ps shall select all processes with the same effective user
       ID as the current  user	and  the  same	controlling  terminal  as  the
       invoker.

OPTIONS
       The  ps	utility	 shall	conform	 to  the  Base	Definitions  volume of
       POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       −a	 Write information for all processes  associated  with	termi‐
		 nals.	 Implementations  may  omit  session leaders from this
		 list.

       −A	 Write information for all processes.

       −d	 Write information for all processes, except session leaders.

       −e	 Write information for all processes.  (Equivalent to −A.)

       −f	 Generate a full listing. (See the STDOUT section for the con‐
		 tents of a full listing.)

       −g grouplist
		 Write	information  for  processes  whose session leaders are
		 given in grouplist.  The application shall  ensure  that  the
		 grouplist  is	a  single argument in the form of a <blank> or
		 <comma>-separated list.

       −G grouplist
		 Write information for processes whose real group  ID  numbers
		 are  given  in	 grouplist.  The application shall ensure that
		 the grouplist is a single argument in the form of  a  <blank>
		 or <comma>-separated list.

       −l	 Generate  a  long  listing. (See STDOUT for the contents of a
		 long listing.)

       −n namelist
		 Specify the name of an alternative system  namelist  file  in
		 place	of  the	 default. The name of the default file and the
		 format of a namelist file are unspecified.

       −o format Write information according to the format specification given
		 in  format.   This  is fully described in the STDOUT section.
		 Multiple −o options can be specified; the  format  specifica‐
		 tion shall be interpreted as the <space>-separated concatena‐
		 tion of all the format option-arguments.

       −p proclist
		 Write information for processes whose process ID numbers  are
		 given	in  proclist.	The  application shall ensure that the
		 proclist is a single argument in the form  of	a  <blank>  or
		 <comma>-separated list.

       −t termlist
		 Write	information  for  processes  associated with terminals
		 given in termlist.  The application  shall  ensure  that  the
		 termlist  is  a  single  argument in the form of a <blank> or
		 <comma>-separated list. Terminal identifiers shall  be	 given
		 in  an implementation-defined format.	On XSI-conformant sys‐
		 tems, they shall be given in one of two forms:	 the  device's
		 filename  (for	 example,  tty04) or, if the device's filename
		 starts with tty, just the identifier following the characters
		 tty (for example, "04").

       −u userlist
		 Write	information  for  processes  whose  user ID numbers or
		 login names are given in  userlist.   The  application	 shall
		 ensure	 that the userlist is a single argument in the form of
		 a <blank> or <comma>-separated	 list.	In  the	 listing,  the
		 numerical  user  ID  shall be written unless the −f option is
		 used, in which case the login name shall be written.

       −U userlist
		 Write information for processes whose real user ID numbers or
		 login	names  are  given  in userlist.	 The application shall
		 ensure that the userlist is a single argument in the form  of
		 a <blank> or <comma>-separated list.

       With  the  exception  of −f, −l, −n namelist, and −o format, all of the
       options shown are used to select processes. If any are  specified,  the
       default	list shall be ignored and ps shall select the processes repre‐
       sented by the inclusive OR of all the selection-criteria options.

OPERANDS
       None.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of ps:

       COLUMNS	 Override the system-selected horizontal  display  line	 size,
		 used  to determine the number of text columns to display. See
		 the Base Definitions volume of POSIX.1‐2008, Chapter 8, Envi‐
		 ronment  Variables  for  valid	 values and results when it is
		 unset or null.

       LANG	 Provide a default value for  the  internationalization	 vari‐
		 ables	that are unset or null. (See the Base Definitions vol‐
		 ume of POSIX.1‐2008, Section 8.2, Internationalization	 Vari‐
		 ables	the  precedence of internationalization variables used
		 to determine the values of locale categories.)

       LC_ALL	 If set to a non-empty string value, override  the  values  of
		 all the other internationalization variables.

       LC_CTYPE	 Determine  the	 locale for the interpretation of sequences of
		 bytes of text data as characters (for example, single-byte as
		 opposed to multi-byte characters in arguments).

       LC_MESSAGES
		 Determine the locale that should be used to affect the format
		 and contents of diagnostic messages written to standard error
		 and informative messages written to standard output.

       LC_TIME	 Determine  the	 format	 and  contents	of  the	 date and time
		 strings displayed.

       NLSPATH	 Determine the location of message catalogs for the processing
		 of LC_MESSAGES.

       TZ	 Determine  the	 timezone  used	 to  calculate	date  and time
		 strings displayed. If TZ is unset  or	null,  an  unspecified
		 default timezone shall be used.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       When  the  −o  option  is  not specified, the standard output format is
       unspecified.

       On XSI-conformant systems, the output format shall be as follows.   The
       column  headings	 and  descriptions  of the columns in a ps listing are
       given below. The precise meanings of these fields  are  implementation-
       defined.	 The  letters 'f' and 'l' (below) indicate the option (full or
       long) that shall cause the corresponding heading to appear;  all	 means
       that  the heading always appears. Note that these two options determine
       only what information is provided for a process; they do not  determine
       which processes are listed.

       F       (l)     Flags  (octal and additive) associated with
		       the process.
       S       (l)     The state of the process.
       UID     (f,l)   The user ID number of  the  process  owner;
		       the  login  name	 is  printed  under the −f
		       option.
       PID     (all)   The process ID of the process; it is possi‐
		       ble  to	kill  a	 process  if this datum is
		       known.
       PPID    (f,l)   The process ID of the parent process.
       C       (f,l)   Processor utilization for scheduling.
       PRI     (l)     The priority of the process; higher numbers
		       mean lower priority.
       NI      (l)     Nice value; used in priority computation.
       ADDR    (l)     The address of the process.
       SZ      (l)     The size in blocks of the core image of the
		       process.
       WCHAN   (l)     The event for which the process is  waiting
		       or  sleeping; if blank, the process is run‐
		       ning.
       STIME   (f)     Starting time of the process.
       TTY     (all)   The controlling terminal for the process.
       TIME    (all)   The  cumulative	execution  time	 for   the
		       process.
       CMD     (all)   The command name; the full command name and
		       its arguments  are  written  under  the	−f
		       option.

       A process that has exited and has a parent, but has not yet been waited
       for by the parent, shall be marked defunct.

       Under the option −f, ps tries to determine the command name  and	 argu‐
       ments  given  when  the	process was created by examining memory or the
       swap area. Failing this, the command name, as it would  appear  without
       the option −f, is written in square brackets.

       The  −o option allows the output format to be specified under user con‐
       trol.

       The application shall ensure that the format specification is a list of
       names  presented	 as  a	single argument, <blank> or <comma>-separated.
       Each variable has a default header. The default header can be  overrid‐
       den  by	appending an <equals-sign> and the new text of the header. The
       rest of the characters in the argument shall  be	 used  as  the	header
       text.  The  fields specified shall be written in the order specified on
       the command line, and should be arranged in columns in the output.  The
       field  widths shall be selected by the system to be at least as wide as
       the header text (default or overridden value). If the  header  text  is
       null,  such  as	−o user=, the field width shall be at least as wide as
       the default header text.	 If all header text fields are null, no header
       line shall be written.

       The following names are recognized in the POSIX locale:

       ruser   The real user ID of the process. This shall be the textual user
	       ID, if it can be obtained and the field	width  permits,	 or  a
	       decimal representation otherwise.

       user    The effective user ID of the process. This shall be the textual
	       user ID, if it can be obtained and the field width permits,  or
	       a decimal representation otherwise.

       rgroup  The  real  group	 ID  of the process. This shall be the textual
	       group ID, if it can be obtained and the field width permits, or
	       a decimal representation otherwise.

       group   The  effective  group ID of the process. This shall be the tex‐
	       tual group ID, if it can be obtained and the field  width  per‐
	       mits, or a decimal representation otherwise.

       pid     The decimal value of the process ID.

       ppid    The decimal value of the parent process ID.

       pgid    The decimal value of the process group ID.

       pcpu    The  ratio  of  CPU time used recently to CPU time available in
	       the same period, expressed as  a	 percentage.  The  meaning  of
	       ``recently''  in	 this  context	is  unspecified.  The CPU time
	       available is determined in an unspecified manner.

       vsz     The size of the process in (virtual) memory in 1024 byte	 units
	       as a decimal integer.

       nice    The decimal value of the nice value of the process; see nice.

       etime   In  the	POSIX  locale,	the elapsed time since the process was
	       started, in the form:

		   [[dd−]hh:]mm:ss

	       where dd shall represent the number of days, hh the  number  of
	       hours,  mm the number of minutes, and ss the number of seconds.
	       The dd field shall be a decimal integer. The  hh,  mm,  and  ss
	       fields  shall  be two-digit decimal integers padded on the left
	       with zeros.

       time    In the POSIX locale, the cumulative CPU time of the process  in
	       the form:

		   [dd−]hh:mm:ss

	       The  dd,	 hh,  mm,  and	ss fields shall be as described in the
	       etime specifier.

       tty     The name of the controlling terminal of the process (if any) in
	       the same format used by the who utility.

       comm    The  name  of  the  command being executed (argv[0] value) as a
	       string.

       args    The command with all its arguments as a string. The implementa‐
	       tion  may  truncate this value to the field width; it is imple‐
	       mentation-defined whether any further truncation occurs. It  is
	       unspecified  whether the string represented is a version of the
	       argument list as it was passed to the command when it  started,
	       or is a version of the arguments as they may have been modified
	       by the application. Applications cannot depend on being able to
	       modify  their  argument	list  and  having that modification be
	       reflected in the output of ps.

       Any field need not be meaningful in all implementations. In such a case
       a <hyphen> ('−') should be output in place of the field value.

       Only  comm and args shall be allowed to contain <blank> characters; all
       others shall not. Any implementation-defined variables shall be	speci‐
       fied  in	 the  system  documentation  along with the default header and
       indicating whether the field may contain <blank> characters.

       The following table specifies the default header	 to  be	 used  in  the
       POSIX locale corresponding to each format specifier.

				TableNames: Variable

       ┌──────────────────────────────────┬───────────────────────────────────┐
       │Format Specifier   Default Header │ Format Specifier   Default Header │
       ├──────────────────────────────────┼───────────────────────────────────┤
       │args		   COMMAND	  │ ppid	       PPID	      │
       │comm		   COMMAND	  │ rgroup	       RGROUP	      │
       │etime		   ELAPSED	  │ ruser	       RUSER	      │
       │group		   GROUP	  │ time	       TIME	      │
       │nice		   NI		  │ tty		       TT	      │
       │pcpu		   %CPU		  │ user	       USER	      │
       │pgid		   PGID		  │ vsz		       VSZ	      │
       │pid		   PID		  │				      │
       └──────────────────────────────────┴───────────────────────────────────┘
STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

	0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       Things  can  change  while ps is running; the snapshot it gives is only
       true for an instant, and might not be accurate by the time it  is  dis‐
       played.

       The  args format specifier is allowed to produce a truncated version of
       the command arguments. In some implementations, this information is  no
       longer available when the ps utility is executed.

       If  the	field  width is too narrow to display a textual ID, the system
       may use a numeric version. Normally, the system would  be  expected  to
       choose  large enough field widths, but if a large number of fields were
       selected to write, it might squeeze fields to their  minimum  sizes  to
       fit  on	one line. One way to ensure adequate width for the textual IDs
       is to override the default header for a field to make  it  larger  than
       most or all user or group names.

       There  is no special quoting mechanism for header text. The header text
       is the rest of the argument. If multiple	 header	 changes  are  needed,
       multiple −o options can be used, such as:

	   ps −o "user=User Name" −o pid=Process\ ID

       On  some implementations, especially multi-level secure systems, ps may
       be severely restricted and produce information only  about  child  pro‐
       cesses owned by the user.

EXAMPLES
       The command:

	   ps −o user,pid,ppid=MOM −o args

       writes at least the following in the POSIX locale:

	     USER   PID	  MOM	COMMAND
	   helene    34	   12	ps −o uid,pid,ppid=MOM −o args

       The contents of the COMMAND field need not be the same in all implemen‐
       tations, due to possible truncation.

RATIONALE
       There is very little commonality between BSD and System	V  implementa‐
       tions  of  ps.	Many options conflict or have subtly different usages.
       The standard developers attempted to select a set of  options  for  the
       base  standard that were useful on a wide range of systems and selected
       options that either can be implemented on both BSD and  System  V-based
       systems	without	 breaking  the	current	 implementations  or where the
       options are sufficiently similar that any changes would not  be	unduly
       problematic for users or implementors.

       It  is  recognized that on some implementations, especially multi-level
       secure systems, ps may be nearly useless. The default output has there‐
       fore been chosen such that it does not break historical implementations
       and also is likely to provide at least some useful information on  most
       systems.

       The  major  change is the addition of the format specification capabil‐
       ity. The motivation for this invention is to provide  a	mechanism  for
       users to access a wider range of system information, if the system per‐
       mits it, in a portable manner. The fields chosen to appear in this vol‐
       ume  of	POSIX.1‐2008  were  arrived at after considering what concepts
       were likely to be both reasonably useful to the	``average''  user  and
       had  a  reasonable  chance of being implemented on a wide range of sys‐
       tems. Again it is recognized that not all systems are able  to  provide
       all  the information and, conversely, some may wish to provide more. It
       is hoped that the approach adopted will be  sufficiently	 flexible  and
       extensible to accommodate most systems. Implementations may be expected
       to introduce new format specifiers.

       The default output should consist of a  short  listing  containing  the
       process	ID, terminal name, cumulative execution time, and command name
       of each process.

       The preference of the standard developers would have been to  make  the
       format  specification  an operand of the ps command. Unfortunately, BSD
       usage precluded this.

       At one time a format was included to display the environment  array  of
       the  process. This was deleted because there is no portable way to dis‐
       play it.

       The −A option is equivalent to the BSD −g and the SVID −e.  Because the
       two systems differed, a mnemonic compromise was selected.

       The −a option is described with some optional behavior because the SVID
       omits session leaders, but BSD does not.

       In an early proposal, format specifiers appeared for priority and start
       time.  The  former  was	not  defined  adequately  in  this  volume  of
       POSIX.1‐2008 and was removed in deference to the	 defined  nice	value;
       the latter because elapsed time was considered to be more useful.

       In a new BSD version of ps, a −O option can be used to write all of the
       default information, followed by additional format specifiers. This was
       not  adopted because the default output is implementation-defined. Nev‐
       ertheless, this is a useful option that should  be  reserved  for  that
       purpose.	 In  the  −o  option for the POSIX Shell and Utilities ps, the
       format is the concatenation of each −o.	Therefore, the user  can  have
       an alias or function that defines the beginning of their desired format
       and add more fields to the end of the output  in	 certain  cases	 where
       that would be useful.

       The format of the terminal name is unspecified, but the descriptions of
       ps, talk, who, and write require that they all use the same format.

       The pcpu field indicates that the CPU time available is	determined  in
       an  unspecified	manner.	 This is because it is difficult to express an
       algorithm that is useful across	all  possible  machine	architectures.
       Historical counterparts to this value have attempted to show percentage
       of use in the recent past, such as the  preceding  minute.  Frequently,
       these  values for all processes did not add up to 100%. Implementations
       are encouraged to provide data in this field to users  that  will  help
       them identify processes currently affecting the performance of the sys‐
       tem.

FUTURE DIRECTIONS
       None.

SEE ALSO
       kill, nice, renice

       The Base Definitions volume of  POSIX.1‐2008,  Chapter  8,  Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT
       Portions	 of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating	System	Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
       cal  and	 Electronics  Engineers,  Inc  and  The	 Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum	 1  applied.)  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the	referee document. The original Standard can be obtained online
       at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,	 see  https://www.ker‐
       nel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group		     2013				PS(1P)
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