PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       ps — report process status

SYNOPSIS         top

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

DESCRIPTION         top

       The ps utility shall write information about processes, subject to
       having 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         top

       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
                 terminals.  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
                 contents 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
                 specification shall be interpreted as the <space>-separated
                 concatenation 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
                 systems, 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
       represented by the inclusive OR of all the selection-criteria
       options.

OPERANDS         top

       None.

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       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,
                 Environment Variables for valid values and results when it
                 is unset or null.

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1‐2008, Section 8.2, Internationalization
                 Variables 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         top

       Default.

STDOUT         top

       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
                       possible 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
                       running.
       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
       arguments 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
       control.

       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 overridden 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
               textual group ID, if it can be obtained and the field width
               permits, 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
               implementation may truncate this value to the field width; it
               is implementation-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
       specified 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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       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
       displayed.

       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
       processes owned by the user.

EXAMPLES         top

       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
       implementations, due to possible truncation.

RATIONALE         top

       There is very little commonality between BSD and System V
       implementations 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
       therefore 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
       capability. The motivation for this invention is to provide a
       mechanism for users to access a wider range of system information, if
       the system permits it, in a portable manner. The fields chosen to
       appear in this volume 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 systems. 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
       display 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. Nevertheless, 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 system.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       kill(1p), nice(1p), renice(1p)

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

COPYRIGHT         top

       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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                              PS(1P)

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