display who is logged in
who utility displays a list of all users currently
logged on, showing for each user the login name, tty name, the date and time
of login, and hostname if not local.
The options are as follows:
- Write column headings above the regular output.
- Only print information about the current terminal. This is the POSIX way
- (Quick.) List only the names and the number of users currently logged on.
When this option is used, all other options are ignored.
- Print a character after the user name indicating the state of the terminal
line: ‘+’ if the terminal is writable; ‘-’ if
it is not; and ‘?’ if a bad line is encountered.
- Print the idle time for each user.
- Returns the invoker's real user name.
- By default,
who gathers information from the file
/var/run/utmp. An alternate
file may be specified which is usually
/var/log/wtmp.[0-6] depending on site policy as
wtmp can grow quite large and daily versions may
or may not be kept around after compression by
wtmp file contains a record of every login,
logout, crash, shutdown and date change since wtmp
was last truncated or created.
If /var/log/wtmp is being used as the
file, the user name may be empty or one of the special characters
~’. Logouts produce an output line
without any user name. For more information on the special characters, see
who utility exits 0 on success,
and >0 if an error occurs.
who utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
The flags [
-abdHlpqrst] are marked by
IEEE Std 1003.1-2008 (“POSIX.1”) as
being an X/Open System Interfaces option. Of these,
-abdlprst] are not supported by this implementation
who utility appeared in
Version 1 AT&T UNIX.