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getutent(3c)

Standard C Library Functions                                      getutent(3C)



NAME
       getutent, getutid, getutline, pututline, setutent, endutent, utmpname -
       user accounting database functions

SYNOPSIS
       #include <utmp.h>

       struct utmp *getutent(void);


       struct utmp *getutid(const struct utmp *id);


       struct utmp *getutline(const struct utmp *line);


       struct utmp *pututline(const struct utmp *utmp);


       void setutent(void);


       void endutent(void);


       int utmpname(const char *file);

DESCRIPTION
       These functions provide access to the user accounting  database,  utmp.
       Entries  in  the  database  are  described  by the definitions and data
       structures in <utmp.h>.


       The utmp structure contains the following members:

         char                ut_user[8];   /* user login name */
         char                ut_id[4];     /* /etc/inittab id */
                                           /* (usually line #) */
         char                ut_line[12];  /* device name (console, lnxx) */
         short               ut_pid;       /* process id */
         short               ut_type;      /* type of entry */
         struct exit_status  ut_exit;      /* exit status of a process */
                                           /* marked as DEAD_PROCESS */
         time_t              ut_time;      /* time entry was made */



       The structure exit_status includes the following members:

         short   e_termination;   /* termination status */
         short   e_exit;          /* exit status */


   getutent()
       The getutent() function reads in the next entry from a  utmp  database.
       If the database is not already open, it opens it. If it reaches the end
       of the database, it fails.

   getutid()
       The getutid() function searches forward from the current point  in  the
       utmp  database  until  it  finds  an  entry  with  a  ut_type  matching
       id->ut_type if the type specified  is  RUN_LVL,  BOOT_TIME,  DOWN_TIME,
       OLD_TIME,  or  NEW_TIME.  If  the type specified in id is INIT_PROCESS,
       LOGIN_PROCESS,  USER_PROCESS,  or  DEAD_PROCESS,  then  getutid()  will
       return a pointer to the first entry whose type is one of these four and
       whose ut_id member matches id->ut_id. If the end of database is reached
       without a match, it fails.

   getutline()
       The getutline() function searches forward from the current point in the
       utmp database until it finds an entry  of  the  type  LOGIN_PROCESS  or
       ut_line  string  matching the line->ut_line string. If the end of data‐
       base is reached without a match, it fails.

   pututline()
       The pututline() function writes the supplied utmp  structure  into  the
       utmp database. It uses getutid() to search forward for the proper place
       if it finds that it is not already at the proper place. It is  expected
       that normally the user of pututline() will have searched for the proper
       entry using one of these functions. If so, pututline() will not search.
       If pututline() does not find a matching slot for the new entry, it will
       add a new entry to the end of the database. It returns a pointer to the
       utmp  structure.  When called by a non-root user, pututline() invokes a
       setuid() root program to verify and write the  entry,  since  the  utmp
       database  is normally writable only by root. In this event, the ut_name
       member must correspond to the actual  user  name  associated  with  the
       process;   the   ut_type   member   must   be  either  USER_PROCESS  or
       DEAD_PROCESS; and the ut_line member must be a device special file  and
       be writable by the user.

   setutent()
       The  setutent() function resets the input stream to the beginning. This
       reset should be done before each search  for  a  new  entry  if  it  is
       desired that the entire database be examined.

   endutent()
       The endutent() function closes the currently open database.

   utmpname()
       The utmpname() function allows the user to change the name of the data‐
       base file examined to another file. If the file does  not  exist,  this
       will  not  be apparent until the first attempt to reference the file is
       made. The utmpname() function does not open the file but closes the old
       file if it is currently open and saves the new file name.

RETURN VALUES
       A  null  pointer  is returned upon failure to read, whether for permis‐
       sions or having reached the end of file, or upon failure to  write.  If
       the file name given is longer than 79 characters, utmpname() returns 0.
       Otherwise, it returns 1.

USAGE
       These functions use buffered standard I/O for  input,  but  pututline()
       uses  an unbuffered non-standard write to avoid race conditions between
       processes trying to modify the utmp and wtmp databases.


       Applications should not access the utmp and  wtmp  databases  directly,
       but should use these functions to ensure that these databases are main‐
       tained consistently. Using these functions, however, may cause applica‐
       tions to fail if user accounting data cannot be represented properly in
       the utmp structure (for example, on a  system  where  PIDs  can  exceed
       32767).  Use  the  functions described on the getutxent(3C) manual page
       instead.

ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE  TYPEAT‐
       TRIBUTE VALUE _ MT-LevelUnsafe


SEE ALSO
       getutxent(3C), ttyslot(3C), utmpx(5), attributes(7)

NOTES
       The  most  current  entry  is  saved  in  a  static structure. Multiple
       accesses require that it be copied before further accesses are made. On
       each call to either getutid() or getutline(), the function examines the
       static structure before performing more I/O. If  the  contents  of  the
       static  structure  match what it is searching for, it looks no further.
       For this reason, to use getutline() to search for multiple occurrences,
       it  would  be necessary to zero out the static area after each success,
       or getutline() would just return  the  same  structure  over  and  over
       again.  There is one exception to the rule about emptying the structure
       before further reads are done. The implicit read  done  by  pututline()
       (if  it  finds that it is not already at the correct place in the file)
       will not hurt the contents of the  static  structure  returned  by  the
       getutent(),  getutid()  or  getutline() functions, if the user has just
       modified those contents and passed the pointer back to pututline().



Oracle Solaris 11.4               15 Apr 2019                     getutent(3C)
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