GETUT(3C)                            SysV                            GETUT(3C)



NAME
     getut: getutent, getutid, getutline, pututline, setutent, endutent,
     utmpname - access utmp file entry

SYNOPSIS
     #include <utmp.h>

     struct utmp *getutent ( )

     struct utmp *getutid (id)
     struct utmp *id;

     struct utmp *getutline (line)
     struct utmp *line;

     void pututline (utmp)
     struct utmp *utmp;

     void setutent ( )

     void endutent ( )

     void utmpname (file)
     char *file;

DESCRIPTION
     getutent, getutid and getutline each return a pointer to a structure of
     the following type:

          struct utmp
            {
          #ifdef apollo
               char ut_user[UTMP_$NAME_SIZE] ;    /* User login name */
          #else
               char ut_user[8] ;        /* User login name */
          #endif
               char ut_id[4] ;          /* /etc/lines id(usually line #) */
               char ut_line[12] ;       /* device name (console, lnxx) */
               short ut_pid ;           /* process id */
               short ut_type ;          /* type of entry */
               struct exit_status
                 {
                   short e_termination ;     /* Process termination status */
                   short e_exit ;       /* Process exit status */
                 }
               ut_exit ;           /* The exit status of a process
                                    * marked as DEAD_PROCESS.
                                    */
               time_t ut_time ;         /* time entry was made */
          #ifdef apollo
              char ut_host[UTMP_$NAME_SIZE] ; /* host name, if remote */
          #endif
               struct entry_loc         /* new fields for node and boot node info */
               {    ut_node_t node;
                    ut_node_t boot_node;
               } ut_loc;
            } ;

     getutent reads in the next entry from a utmp-like file.  If the file is
     not already open, it opens it.  If it reaches the end of the file, it
     fails.

     getutid searches forward from the current point in the utmp file until it
     finds an entry with a ut_type matching id->ut_type if the type specified
     is RUN_LVL, BOOT_TIME, OLD_TIME or NEW_TIME.  If the type specified in id
     is INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS or DEAD_PROCESS, then
     getutid will return a pointer to the first entry whose type is one of
     these four and whose ut_id field matches id->ut_id.  If the end of file
     is reached without a match, it fails.

     getutline searches forward from the current point in the utmp file until
     it finds an entry of the type LOGIN_PROCESS or USER_PROCESS which also
     has a ut_line string matching the line->ut_line string.  If the end of
     file is reached without a match, it fails.

     pututline writes out the supplied utmp structure into the utmp file.  It
     uses getutid to search forward for the proper place if it finds that it
     is not already at the proper place.  It is expected that normally the
     user of pututline will have searched for the proper entry using one of
     the getut routines.  If so, pututline will not search.  If pututline does
     not find a matching slot for the new entry, it will add a new entry to
     the end of the file.

     setutent resets the input stream to the beginning of the file.  This
     should be done before each search for a new entry if it is desired that
     the entire file be examined.

     endutent closes the currently open file.

     utmpname allows the user to change the name of the file examined, from
     /etc/utmp to any other file.  It is most often expected that this other
     file will be /etc/wtmp.  If the file does not exist, this will not be
     apparent until the first attempt to reference the file is made.  utmpname
     does not open the file.  It just closes the old file if it is currently
     open and saves the new filename.

FILES
     /etc/utmp
     /etc/wtmp

SEE ALSO
     ttyslot(3C), utmp(4).

DIAGNOSTICS
     A NULL pointer is returned upon failure to read, whether for permissions
     or having reached the end of file, or upon failure to write.

NOTES
     The most current entry is saved in a static structure.  Multiple accesses
     require that it be copied before further accesses are made.  Each call to
     either getutid or getutline sees the routine examine the static structure
     before performing more I/O.  If the contents of the static structure
     match what it is searching for, it looks no further.  For this reason to
     use getutline to search for multiple occurrences, it would be necessary
     to zero out the static after each success, or getutline would just return
     the same pointer over and over again.  There is one exception to the rule
     about removing the structure before further reads are done.  The implicit
     read done by pututline (if it finds that it is not already at the correct
     place in the file) will not hurt the contents of the static structure
     returned by the getutent, getutid or getutline routines, if the user has
     just modified those contents and passed the pointer back to pututline.

     These routines use buffered standard I/O for input, but pututline uses an
     unbuffered non-standard write to avoid race conditions between processes
     trying to modify the utmp and wtmp files.