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GETUTENT(3)		   Linux Programmers Manual		  GETUTENT(3)

       getutent, getutid, getutline, pututline, setutent, endutent, utmpname -
       access utmp file entries


       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);

       int utmpname(const char *file);

       New applications should use the POSIX.1-specified "utmpx"  versions  of
       these functions; see CONFORMING TO.

       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 .

       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

       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.  The definition of this structure is shown in utmp(5).

       getutid()  searches  forward from the current file position in the utmp
       file based upon ut.  If	ut->ut_type  is  one  of  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_PRO
       CESS, 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 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.

       getutent(),  getutid(),	and  getutline()  return a pointer to a struct
       utmp on success, and NULL on failure (which includes  the  "record  not
       found" case).  This struct utmp is allocated in static storage, and may
       be overwritten by subsequent calls.

       On success pututline() returns ut; on failure, it returns NULL.

       utmpname() returns 0 if the new name was successfully stored, or -1  on

       ENOMEM Out of memory.

       ESRCH  Record not found.

       setutent(),  pututent(),  and the getut* () functions can also fail for
       the reasons described in open(2).

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

       XPG2, SVr4.

       In XPG2 and SVID 2 the function pututline()  is	documented  to	return
       void,  and  that  is  what  it  does on many systems (AIX, HP-UX, Linux
       libc5).	HP-UX introduces a new function _pututline() with  the	proto
       type given above for pututline() (also found in Linux libc5).

       All   these   functions	 are   obsolete   now  on  non-Linux  systems.
       POSIX.1-2001, following SUSv1, does not have any  of  these  functions,
       but instead uses


       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);

       These  functions  are  provided	by glibc, and perform the same task as
       their equivalents without the "x", but use  struct  utmpx,  defined  on
       Linux to be the same as struct utmp.  For completeness, glibc also pro
       vides utmpxname(), although this function is not specified by  POSIX.1.

       On  some  other	systems, the utmpx structure is a superset of the utmp
       structure, with additional fields, and larger versions of the  existing
       fields,	and  parallel  files  are  maintained,	often /var/*/utmpx and

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

   Glibc Notes
       The above functions are not thread-safe.  Glibc adds reentrant versions

       #define _GNU_SOURCE    /* or _SVID_SOURCE or _BSD_SOURCE */

       int getutent_r(struct utmp *ubuf, struct utmp **ubufp);

       int getutid_r(struct utmp *ut,
		     struct utmp *ubuf, struct utmp **ubufp);

       int getutline_r(struct utmp *ut,
		       struct utmp *ubuf, struct utmp **ubufp);

       These  functions  are  GNU  extensions, analogs of the functions of the
       same name without the _r suffix.  The ubuf argument gives  these  func
       tions  a  place to store their result.  On success they return 0, and a
       pointer to the result is written in *ubufp.  On error  these  functions
       return  -1.   There  are  no  utmpx equivalents of the above functions.
       (POSIX.1 does not specify such functions.)

       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(3) and ttyname(3).


       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(STDIN_FILENO) + strlen("/dev/"));
	   /* only correct for ptys named /dev/tty[pqr][0-9a-z] */
	   strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
	   strcpy(entry.ut_user, getpwuid(getuid())->pw_name);
	   memset(entry.ut_host, 0, UT_HOSTSIZE);
	   entry.ut_addr = 0;

	   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);

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


       getutmp(3), utmp(5), feature_test_macros(7)

       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of	the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

				  2008-06-29			   GETUTENT(3)

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