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GETGRGID(P)		   POSIX Programmer's Manual		   GETGRGID(P)

NAME
       getgrgid, getgrgid_r - get group database entry for a group ID

SYNOPSIS
       #include <grp.h>

       struct group *getgrgid(gid_t gid);

       int getgrgid_r(gid_t gid, struct group *grp, char *buffer,
	      size_t bufsize, struct group **result);

DESCRIPTION
       The  getgrgid()	function  shall search the group database for an entry
       with a matching gid.

       The getgrgid() function need not be reentrant. A function that  is  not
       required to be reentrant is not required to be thread-safe.

       The  getgrgid_r()  function shall update the group structure pointed to
       by grp and store a pointer to that structure at the location pointed to
       by result. The structure shall contain an entry from the group database
       with a matching gid. Storage referenced by the group structure is allo‐
       cated from the memory provided with the buffer parameter, which is buf‐
       size bytes in size. The maximum size needed  for	 this  buffer  can  be
       determined  with the {_SC_GETGR_R_SIZE_MAX} sysconf() parameter. A NULL
       pointer shall be returned at the location pointed to by result on error
       or if the requested entry is not found.

RETURN VALUE
       Upon  successful	 completion,  getgrgid()  shall	 return a pointer to a
       struct group with the structure defined	in  <grp.h>  with  a  matching
       entry  if  one  is  found.  The getgrgid() function shall return a null
       pointer if either the requested	entry  was  not	 found,	 or  an	 error
       occurred. On error, errno shall be set to indicate the error.

       The  return  value may point to a static area which is overwritten by a
       subsequent call to getgrent(), getgrgid(), or getgrnam().

       If successful, the getgrgid_r() function shall return zero;  otherwise,
       an error number shall be returned to indicate the error.

ERRORS
       The getgrgid() and getgrgid_r() functions may fail if:

       EIO    An I/O error has occurred.

       EINTR  A signal was caught during getgrgid().

       EMFILE {OPEN_MAX}  file	descriptors  are currently open in the calling
	      process.

       ENFILE The maximum allowable number of files is currently open  in  the
	      system.

       The getgrgid_r() function may fail if:

       ERANGE Insufficient storage was supplied via buffer and bufsize to con‐
	      tain the data to be referenced by the resulting group structure.

       The following sections are informative.

EXAMPLES
   Finding an Entry in the Group Database
       The following example uses getgrgid() to search the group database  for
       a  group ID that was previously stored in a stat structure, then prints
       out the group name if it is found.  If the group is not found, the pro‐
       gram prints the numeric value of the group for the entry.

	      #include <sys/types.h>
	      #include <grp.h>
	      #include <stdio.h>
	      ...
	      struct stat statbuf;
	      struct group *grp;
	      ...
	      if ((grp = getgrgid(statbuf.st_gid)) != NULL)
		  printf(" %-8.8s", grp->gr_name);
	      else
		  printf(" %-8d", statbuf.st_gid);
	      ...

APPLICATION USAGE
       Applications  wishing to check for error situations should set errno to
       0 before calling getgrgid(). If	errno  is  set	on  return,  an	 error
       occurred.

       The  getgrgid_r()  function is thread-safe and shall return values in a
       user-supplied buffer instead of possibly using a static data area  that
       may be overwritten by each call.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       endgrent()   ,	getgrnam()   ,	 the   Base   Definitions   volume  of
       IEEE Std 1003.1-2001, <grp.h>, <limits.h>, <sys/types.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the	referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			   GETGRGID(P)
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