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Linux 2.6 - man page for getgrgid_r (linux section 3posix)

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

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

       #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);

       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 reen-
       trant 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 con-
       tain an entry from the group database with a matching gid. Storage referenced by the group
       structure  is  allocated 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 loca-
       tion pointed to by result on error or if the requested entry is not found.

       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() func-
       tion 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.

       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 contain the data to be
	      referenced by the resulting group structure.

       The following sections are informative.

   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 program 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);
		  printf(" %-8d", statbuf.st_gid);

       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.



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

       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				      GETGRGID(P)

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