GETUTENT(3)

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

SYNOPSIS
       #include <<utmp.h>>

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

       void pututline(struct utmp *ut);

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

       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 &lt;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(), and getutline() return a pointer to
       a static struct utmp.

ERRORS
       On error, (struct utmp*)0 will be returned.

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(0)+strlen("/dev/"));
         /* only correct for ptys named /dev/tty[pqr][0-9a-z] */
         strcpy(entry.ut_id,ttyname(0)+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

SEE ALSO
       utmp(5)