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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 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 3.22 of the Linux man-pages project.  A description of the project, and informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                               2004-05-06                          LOGIN(3)