man who – Man page for who

June 1, 2007 – 1:20 am

WHO


Section: POSIX Programmer’s Manual (P)
Updated: 2003
Index
Return to Main Contents

 

NAME

who – display who is on the system
 

SYNOPSIS

who [–mTu]



who
[–mu]–s[–bHlprt][file]


who
[–mTu][–abdHlprt][file]


who –q
[file]


who am i


who am I




 

DESCRIPTION

The who utility shall list various pieces of information about
accessible users. The domain of accessibility is
implementation–defined.

Based on the options given, who can also list the user’s name,
terminal line, login time, elapsed time since activity
occurred on the line, and the process ID of the command interpreter
for each current system user.
 

OPTIONS

The who 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. The metavariables, such
as <line>, refer to fields described in the
STDOUT section.


–a

Process the implementation–defined database or named file with the
–b, –d, –l, –p, –r,
–t, –T and –u options turned on.
–b

Write the time and date of the last reboot.
–d

Write a list of all processes that have expired and not been respawned
by the init system process. The <exit>
field shall appear for dead processes and contain the termination
and exit values of the dead process. This can be useful in
determining why a process terminated.
–H

Write column headings above the regular output.
–l

(The letter ell.) List only those lines on which the system is waiting
for someone to login. The <name> field shall be
LOGIN in such cases. Other fields shall be the same as for user
entries except that the <state> field does not
exist.
–m

Output only information about the current terminal.
–p

List any other process that is currently active and has been previously
spawned by init.
–q

(Quick.) List only the names and the number of users currently logged
on. When this option is used, all other options shall be
ignored.
–r

Write the current run–level of the init process.
–s

List only the <name>, <line>, and <time> fields.
This is the default case.
–t

Indicate the last change to the system clock.
–T

Show the state of each terminal, as described in the STDOUT section.
–u

Write "idle time" for each displayed user in addition to any other
information. The idle time is the time since any activity
occurred on the user’s terminal. The method of determining this is
unspecified.  This option
shall list only those users who are currently logged in. The <name>
is the user’s login name. The <line>
is the name of the line as found in the directory /dev. The
<time> is the time that the user logged in. The
<activity> is the number of hours and minutes since activity
last occurred on that particular line. A dot indicates
that the terminal has seen activity in the last minute and is therefore
"current". If more than twenty–four hours have elapsed or
the line has not been used since boot time, the entry shall be marked
<old>. This field is useful when trying to
determine whether a person is working at the terminal or not. The
<pid> is the process ID of the user’s login process.



 

OPERANDS

The following operands shall be supported:


am iam I

In the POSIX locale, limit the output to describing the invoking user,
equivalent to the –m option. The am and
i or I must be separate arguments.
file

Specify a pathname of a file to substitute for the implementation–defined
database of logged–on users that who uses by
default.



 

STDIN

Not used.
 

INPUT FILES

None.
 

ENVIRONMENT VARIABLES

The following environment variables shall affect the execution of
who:


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 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.
LC_TIME

Determine the locale used for the format and contents of the date
and time strings.
NLSPATH

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

TZ

Determine the timezone used when writing date and time information.
If TZ is unset or null, an unspecified default
timezone shall be used.



 

ASYNCHRONOUS EVENTS

Default.
 

STDOUT

The who utility shall write its default format to the standard
output in an implementation–defined format, subject only
to the requirement of containing the information described above.

XSI–conformant systems shall write the default information to the
standard output in the following general format:



<name>[<state>]<line><time>[<activity>][<pid>][<comment>][<exit>]

The following format shall be used for the –T option:



"%s %c %s %s\n" <name>, <terminal state>, <terminal name>,
<
time of login>

where <terminal state> is one of the following characters:


+

The terminal allows write access to other users.

The terminal denies write access to other users.
?

The terminal write–access state cannot be determined.



In the POSIX locale, the <time of login> shall be equivalent
in format to the output of:



date +"%b %e %H:%M"

If the –u option is used with –T, the idle time shall
be added to the end of the previous format in an unspecified
format.
 

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

The name init used for the system process is the most commonly
used on historical systems, but it may vary.

The "domain of accessibility" referred to is a broad concept that
permits interpretation either on a very secure basis or even
to allow a network–wide implementation like the historical rwho.
 

EXAMPLES

None.
 

RATIONALE

Due to differences between historical implementations, the base options
provided were a compromise to allow users to work with
those functions. The standard developers also considered removing
all the options, but felt that these options offered users
valuable functionality. Additional options to match historical systems
are available on XSI–conformant systems.

It is recognized that the who command may be of limited usefulness,
especially in a multi–level secure environment. The
standard developers considered, however, that having some standard
method of determining the "accessibility" of other users would
aid user portability.

No format was specified for the default who output for systems
not supporting the XSI Extension. In such a user–oriented
command, designed only for human use, this was not considered to be
a deficiency.

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

It is acceptable for an implementation to produce no output for an
invocation of who mil.
 

FUTURE DIRECTIONS

None.
 

SEE ALSO

mesg
 

COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
–– Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001–2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .



 

Index



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



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