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
       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 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_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.

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 additional 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 structure is already large enough. The functions getutxent etc. are aliases
       for getutent etc.

SEE ALSO

       utmp(5)

								    1996-07-25							       GETUTENT(3)