getutid

GETUTENT(3)                    Library functions                   GETUTENT(3)



NAME
       getutent, getutid, getutline, pututline, setutent, endutent, 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);

       struct utmp *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 <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  func-
       tions.

       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 containing 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_PRO-
       CESS, 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 position 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(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

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

       The utmpx structure is a superset of the  utmp  structure,  with  addi-
       tional  fields, and larger versions of the existing fields.  The corre-
       sponding files are often /var/*/utmpx and /var/*/wtmpx.

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

SEE ALSO
       utmp(5)



                                  1996-07-25                       GETUTENT(3)