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GETGRGID(3P)               POSIX Programmer's Manual              GETGRGID(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
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(3P)