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LOGIN(3)			    Linux Programmer's Manual				 LOGIN(3)

NAME
       login, logout - write utmp and wtmp entries

SYNOPSIS
       #include <utmp.h>

       void login(const struct utmp *ut);

       int logout(const char *ut_line);

       Link with -lutil.

DESCRIPTION
       The utmp file records who is currently using the system.  The wtmp file records all logins
       and logouts.  See utmp(5).

       The function login() takes the supplied struct utmp, ut, and writes it to  both	the  utmp
       and the wtmp file.

       The function logout() clears the entry in the utmp file again.

   GNU details
       More  precisely,  login()  takes  the  argument ut struct, fills the field ut->ut_type (if
       there is such a field) with the value USER_PROCESS, and fills  the  field  ut->ut_pid  (if
       there  is such a field) with the process ID of the calling process.  Then it tries to fill
       the field ut->ut_line.  It takes the first of stdin, stdout, stderr that  is  a	terminal,
       and  stores the corresponding pathname minus a possible leading /dev/ into this field, and
       then writes the struct to the utmp file.  On the other  hand,  if  no  terminal	name  was
       found,  this  field  is filled with "???"  and the struct is not written to the utmp file.
       After this, the struct is written to the wtmp file.

       The logout() function searches the utmp file for an entry matching the  ut_line	argument.
       If  a record is found, it is updated by zeroing out the ut_name and ut_host fields, updat-
       ing the ut_tv timestamp	field  and  setting  ut_type  (if  there  is  such  a  field)  to
       DEAD_PROCESS.

RETURN VALUE
       The  logout() function returns 1 if the entry was successfully written to the database, or
       0 if an error occurred.

FILES
       /var/run/utmp
	      user accounting database, configured through _PATH_UTMP in <paths.h>

       /var/log/wtmp
	      user accounting log file, configured through _PATH_WTMP in <paths.h>

CONFORMING TO
       Not in POSIX.1-2001.  Present on the BSDs.

NOTES
       Note that the member ut_user of struct utmp is called ut_name in BSD.  Therefore,  ut_name
       is defined as an alias for ut_user in <utmp.h>.

SEE ALSO
       getutent(3), utmp(5)

COLOPHON
       This  page  is  part of release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at
       http://www.kernel.org/doc/man-pages/.

GNU					    2004-05-06					 LOGIN(3)
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