ps(1p) - phpMan

PS(P) PS(P)

NAME
ps - report process status

SYNOPSIS
ps [-aA][-defl][-G grouplist][-o format]...[-p proclist][-t termlist]

[-U userlist][-g grouplist][-n namelist][-u userlist]

DESCRIPTION
The ps utility shall write information about processes, subject to having the
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
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

The following options shall be supported:

-a Write information for all processes associated with terminals. Implementa-
tions 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 grou-
plist. 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 argu-
ment 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>-sep-
arated concatenation of all the format option-arguments.

-p proclist
Write information for processes whose process ID numbers are given in pro-
clist. 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 deviceâ€™s filename (for example,
tty04) or, if the deviceâ€™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 sin-
gle argument in the form of a <blank> or comma-separated list. In the list-
ing, 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 -o format, all of the options shown are used to select pro-
cesses. 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
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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001,
Section 8.2, Internationalization Variables for the precedence of interna-
tionalization 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 char-
acters 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 head-
ings and descriptions of the columns in a ps listing are given below. The precise
meanings of these fields are implementation-defined. The letters â€â€™fâ€â€™ and â€â€™lâ€â€™
(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 num-
bers mean lower priority.
NI (l) Nice value; used in priority computa-
tion.
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 wait-
ing or sleeping; if blank, the process
is running.
STIME (f) Starting time of the process.
TTY (all) The controlling terminal for the pro-
cess.
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 pre-
sented 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 speci-
fied 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 representa-
tion 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 man-
ner.

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 trun-
cate 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 (
â€â€™-â€â€™ ) should be output in place of the field value.

Only comm and args shall be allowed to contain <blank>s; 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>s.

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

Table: Variable Names and Default Headers in ps

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 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 ade-
quate 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
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
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 sys-
tems, 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 moti-
vation 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 IEEE Std 1003.1-2001 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 speci-
fication 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 ses-
sion 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 IEEE Std 1003.1-2001 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 use-
ful.

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 unspeci-
fied 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%. Imple-
mentations 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
None.