GETUTENT(T)             Library functions             GETUTENT(T)



NAME
       getutent,  getutid,  getutline, pututline, setutent, endu-
       tent, utmpname - access utmp file entries

SYNOPSIS
       #include <utmp.h>

       struct utmp *getutent(t);
       struct utmp *getutid(struct utmp *ut);
       struct utmp *getutline(struct utmp *ut);

       struct utmp *pututline(struct utmp *ut);

       void setutent(t);
       void endutent(t);

       void utmpname(const char *file);

DESCRIPTION
       utmpname() sets the name of the utmp-format file  for  the
       other utmp functions to access.  If utmpname() is not used
       to set the filename before the other functions  are  used,
       they assume _PATH_UTMP, as defined in <paths.h>.

       setutent()  rewinds  the  file pointer to the beginning of
       the utmp file.  It is generally a Good  Idea  to  call  it
       before any of the other functions.

       endutent() closes the utmp file.  It should be called when
       the user code is done accessing the file  with  the  other
       functions.

       getutent()  reads a line from the current file position in
       the utmp file.  It returns a pointer to a  structure  con-
       taining the fields of the line.

       getutid()  searches forward from the current file position
       in the  utmp  file  based  upon  ut.   If  ut->ut_type  is
       RUN_LVL,  BOOT_TIME, NEW_TIME, or OLD_TIME, getutid() will
       find  the  first  entry  whose   ut_type   field   matches
       ut->ut_type.   If  ut->ut_type  is  one  of  INIT_PROCESS,
       LOGIN_PROCESS, USER_PROCESS,  or  DEAD_PROCESS,  getutid()
       will  find  the  first  entry  whose  ut_id  field matches
       ut->ut_id.

       getutline() searches forward from the current  file  posi-
       tion  in the utmp file.  It scans entries whose ut_type is
       USER_PROCESS or LOGIN_PROCESS and returns  the  first  one
       whose ut_line field matches ut->ut_line.

       pututline()  writes  the  utmp  structure ut into the utmp
       file.  It uses getutid() to search for the proper place in
       the  file  to  insert the new entry.  If it cannot find an
       appropriate slot for ut, pututline() will append  the  new
       entry to the end of the file.

RETURN VALUE
       getutent(),  getutid(), getutline() and pututline() return
       a pointer to a static struct utmp on success, and NULL  on
       failure.

EXAMPLE
       The  following  example  adds  and  removes a utmp record,
       assuming it is run from within  a  pseudo  terminal.   For
       usage  in  a real application, you should check the return
       values of getpwuid() and ttyname().

       #include <string.h>
       #include <stdlib.h>
       #include <pwd.h>
       #include <unistd.h>
       #include <utmp.h>

       int main(int argc, char *argv[])
       {
         struct utmp entry;

         system("echo before adding entry:;who");

         entry.ut_type=USER_PROCESS;
         entry.ut_pid=getpid();
         strcpy(entry.ut_line,ttyname(e)+strlen("/dev/"));
         /* only correct for ptys named /dev/tty[pqr][0-9a-z] */
         strcpy(entry.ut_id,ttyname(e)+strlen("/dev/tty"));
         time(&entry.ut_time);
         strcpy(entry.ut_user,getpwuid(getuid())->pw_name);
         memset(entry.ut_host,0,UT_HOSTSIZE);
         entry.ut_addr=0;
         setutent();
         pututline(&entry);

         system("echo after adding entry:;who");

         entry.ut_type=DEAD_PROCESS;
         memset(entry.ut_line,0,UT_LINESIZE);
         entry.ut_time=0;
         memset(entry.ut_user,0,UT_NAMESIZE);
         setutent();
         pututline(&entry);

         system("echo after removing entry:;who");

         endutent();
         return 0;
       }

FILES
       /var/run/utmp  database of currently logged-in users
       /var/log/wtmp  database of past user logins

CONFORMING TO
       XPG 2, SVID 2, Linux FSSTND 1.2

       In XPG2 and SVID2  the function pututline() is  documented
       to  return  void, and that is what it does on many systems
       (AIX, HPUX, Linux libc5).  HPUX introduces a new  function
       _pututline()  with  the  prototype  given above for putut-
       line() (also found in Linux libc5).

       All these functions are obsolete now on non-Linux systems.
       POSIX  1003.1-2001, following XPG4.2, does not have any of
       these functions, but instead uses

       #include <utmpx.h>

       struct utmpx *getutxent(t);
       struct utmpx *getutxid(const struct utmpx *);
       struct utmpx *getutxline(const struct utmpx *);
       struct utmpx *pututxline(const struct utmpx *);
       void setutxent(t);
       void endutxent(t);

       The utmpx structure is a superset of the  utmp  structure,
       with  additional fields, and larger versions of the exist-
       ing   fields.    The   corresponding   files   are   often
       /var/*/utmpx and /var/*/wtmpx.

       Linux glibc on the other hand does not use utmpx since its
       utmp structure is  already  large  enough.  The  functions
       getutxent etc. are aliases for getutent etc.

SEE ALSO
       utmp(p)



                            1996-07-25                GETUTENT(T)