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 tty, 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 tty 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, updating 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 3.27 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)