1WHO(1P)                    POSIX Programmer's Manual                   WHO(1P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
10

NAME

12       who — display who is on the system
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SYNOPSIS

15       who [-mTu] [-abdHlprt] [file]
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17       who [-mu] -s [-bHlprt] [file]
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19       who -q [file]
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21       who am i
22
23       who am I
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DESCRIPTION

26       The who utility shall list various pieces of information about accessi‐
27       ble users. The domain of accessibility is implementation-defined.
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29       Based on the options given, who can also list the user's name, terminal
30       line, login time, elapsed time since activity occurred on the line, and
31       the process ID of the command interpreter for each current system user.
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OPTIONS

34       The  who  utility  shall  conform  to  the  Base  Definitions volume of
35       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
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37       The following options shall be supported. The  metavariables,  such  as
38       <line>, refer to fields described in the STDOUT section.
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40       -a        Process  the  implementation-defined  database  or named file
41                 with the -b, -d, -l, -p, -r, -t, -T and -u options turned on.
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43       -b        Write the time and date of the last system reboot. The system
44                 reboot  time  is the time at which the implementation is able
45                 to commence running processes.
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47       -d        Write a list of all processes that have expired and not  been
48                 respawned  by the init system process. The <exit> field shall
49                 appear for dead processes and  contain  the  termination  and
50                 exit values of the dead process. This can be useful in deter‐
51                 mining why a process terminated.
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53       -H        Write column headings above the regular output.
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55       -l        (The letter ell.) List only those lines on which  the  system
56                 is  waiting  for  someone to login. The <name> field shall be
57                 LOGIN in such cases. Other fields shall be the  same  as  for
58                 user entries except that the <state> field does not exist.
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60       -m        Output only information about the current terminal.
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62       -p        List  any other process that is currently active and has been
63                 previously spawned by init.
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65       -q        (Quick.) List only the names and the  number  of  users  cur‐
66                 rently logged on. When this option is used, all other options
67                 shall be ignored.
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69       -r        Write the current run-level of the init process.
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71       -s        List only the <name>, <line>, and <time> fields.  This is the
72                 default case.
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74       -t        Indicate the last change to the system clock.
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76       -T        Show  the  state of each terminal, as described in the STDOUT
77                 section.
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79       -u        Write ``idle time'' for each displayed user  in  addition  to
80                 any  other  information.  The idle time is the time since any
81                 activity occurred on  the  user's  terminal.  The  method  of
82                 determining this is unspecified.  This option shall list only
83                 those users who are currently logged in.  The <name>  is  the
84                 user's  login  name.  The  <line>  is the name of the line as
85                 found in the directory /dev.  The <time> is the time that the
86                 user  logged  in.  The  <activity> is the number of hours and
87                 minutes since activity last occurred on that particular line.
88                 A  dot  indicates  that the terminal has seen activity in the
89                 last minute  and  is  therefore  ``current''.  If  more  than
90                 twenty-four  hours have elapsed or the line has not been used
91                 since boot time, the entry shall be marked <old>. This  field
92                 is  useful when trying to determine whether a person is work‐
93                 ing at the terminal or not. The <pid> is the  process  ID  of
94                 the user's login process.
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OPERANDS

97       The following operands shall be supported:
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99       am i, am I
100                 In  the  POSIX  locale,  limit  the  output to describing the
101                 invoking user, equivalent to the -m option. The am and i or I
102                 must be separate arguments.
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104       file      Specify  a pathname of a file to substitute for the implemen‐
105                 tation-defined database of logged-on users that who  uses  by
106                 default.
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STDIN

109       Not used.
110

INPUT FILES

112       None.
113

ENVIRONMENT VARIABLES

115       The following environment variables shall affect the execution of who:
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117       LANG      Provide  a  default  value for the internationalization vari‐
118                 ables that are unset or null. (See the Base Definitions  vol‐
119                 ume  of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
120                 ables for the precedence  of  internationalization  variables
121                 used to determine the values of locale categories.)
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123       LC_ALL    If  set  to  a non-empty string value, override the values of
124                 all the other internationalization variables.
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126       LC_CTYPE  Determine the locale for the interpretation of  sequences  of
127                 bytes of text data as characters (for example, single-byte as
128                 opposed to multi-byte characters in arguments).
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130       LC_MESSAGES
131                 Determine the locale that should be used to affect the format
132                 and  contents  of  diagnostic  messages  written  to standard
133                 error.
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135       LC_TIME   Determine the locale used for the format and contents of  the
136                 date and time strings.
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138       NLSPATH   Determine the location of message catalogs for the processing
139                 of LC_MESSAGES.
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141       TZ        Determine the timezone used when writing date and time infor‐
142                 mation.  If TZ is unset or null, an unspecified default time‐
143                 zone shall be used.
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ASYNCHRONOUS EVENTS

146       Default.
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STDOUT

149       The who utility shall write its default format to the  standard  output
150       in an implementation-defined format, subject only to the requirement of
151       containing the information described above.
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153       XSI-conformant systems shall write the default information to the stan‐
154       dard output in the following general format:
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157           <name>[<state>]<line><time>[<activity>][<pid>][<comment>][<exit>]
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159       For the -b option, <line> shall be "systemboot".  The <name> is unspec‐
160       ified.
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162       The following format shall be used for the -T option:
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164
165           "%s %c %s %s\n" <name>, <terminal state>, <terminal name>,
166               <time of login>
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168       where <terminal state> is one of the following characters:
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170       +       The terminal allows write access to other users.
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172       -       The terminal denies write access to other users.
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174       ?       The terminal write-access state cannot be determined.
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176       <space> This entry is not associated with a terminal.
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178       In the POSIX locale, the <time of login> shall be equivalent in  format
179       to the output of:
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181
182           date +"%b %e %H:%M"
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184       If  the  -u option is used with -T, the idle time shall be added to the
185       end of the previous format in an unspecified format.
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STDERR

188       The standard error shall be used only for diagnostic messages.
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OUTPUT FILES

191       None.
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EXTENDED DESCRIPTION

194       None.
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EXIT STATUS

197       The following exit values shall be returned:
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199        0    Successful completion.
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201       >0    An error occurred.
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CONSEQUENCES OF ERRORS

204       Default.
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206       The following sections are informative.
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APPLICATION USAGE

209       The name init used for the system process is the most commonly used  on
210       historical systems, but it may vary.
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212       The  ``domain  of  accessibility''  referred to is a broad concept that
213       permits interpretation either on a very secure basis or even to allow a
214       network-wide implementation like the historical rwho.
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EXAMPLES

217       None.
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RATIONALE

220       Due to differences between historical implementations, the base options
221       provided were a compromise to allow users to work with those functions.
222       The  standard  developers also considered removing all the options, but
223       felt that these options offered  users  valuable  functionality.  Addi‐
224       tional options to match historical systems are available on XSI-confor‐
225       mant systems.
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227       It is recognized that the who command may  be  of  limited  usefulness,
228       especially in a multi-level secure environment. The standard developers
229       considered, however, that having some standard  method  of  determining
230       the ``accessibility'' of other users would aid user portability.
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232       No format was specified for the default who output for systems not sup‐
233       porting the XSI option. In such a user-oriented command, designed  only
234       for human use, this was not considered to be a deficiency.
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236       The format of the terminal name is unspecified, but the descriptions of
237       ps, talk, and write require that they use the same format.
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239       It is acceptable for an implementation to  produce  no  output  for  an
240       invocation of who mil.
241

FUTURE DIRECTIONS

243       None.
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SEE ALSO

246       mesg
247
248       The  Base  Definitions  volume  of POSIX.1‐2017, Chapter 8, Environment
249       Variables, Section 12.2, Utility Syntax Guidelines
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252       Portions of this text are reprinted and reproduced in  electronic  form
253       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
254       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
255       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
256       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
257       event of any discrepancy between this version and the original IEEE and
258       The Open Group Standard, the original IEEE and The Open Group  Standard
259       is  the  referee document. The original Standard can be obtained online
260       at http://www.opengroup.org/unix/online.html .
261
262       Any typographical or formatting errors that appear  in  this  page  are
263       most likely to have been introduced during the conversion of the source
264       files to man page format. To report such errors,  see  https://www.ker
265       nel.org/doc/man-pages/reporting_bugs.html .
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269IEEE/The Open Group                  2017                              WHO(1P)
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