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LOGIN(3)                  Linux System Administration                 LOGIN(3)



NAME
       login(1,3,5), logout - write(1,2) utmp and wtmp entries

SYNOPSIS
       #include <utmp.h>

       void login(1,3,5)(const struct utmp *ut);
       int logout(const char *ut_line);

DESCRIPTION
       The utmp file(1,n) records who is currently using the system.  The wtmp file(1,n)
       records all logins and logouts. See utmp(5).

       The function login(1,3,5)() takes the supplied struct utmp ut, and  writes  it
       to both utmp and wtmp file.

       The function logout() clears the entry in(1,8) the utmp file(1,n) again.

GNU DETAILS
       More  precisely,  login(1,3,5)() takes the argument ut struct, fills the field
       ut->ut_type (if(3,n) there is such a field) with the value USER_PROCESS, and
       fills  the field ut->ut_pid (if(3,n) 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(1,4), 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(3,n) no tty(1,4) 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(1,n) 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(3,n) there is such a field) to DEAD_PROCESS.

RETURN VALUES
       The  logout()  function returns 1 if(3,n) the entry was successfully written
       to the database, or 0 if(3,n) an error(8,n) occurred.

NOTE
       These functions are included in(1,8)  libutil,  hence  you'll  need  to  add
       -lutil to your compiler commandline.

       Note  that  the member ut_user of struct utmp is called ut_name in(1,8) BSD.
       Therefore, ut_name is defined as an alias for ut_user in(1,8) utmp.h.

FILES
       /var/run/utmp
              user  accounting  database,  configured  through  _PATH_UTMP  in(1,8)
              <paths.h>

       /var/log/wtmp
              user  accounting  log  file(1,n),  configured  through  _PATH_WTMP in(1,8)
              <paths.h>

SEE ALSO
       getutent(3), utmp(5)



GNU/Linux                         2004-05-06                          LOGIN(3)

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