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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 dif-
       fer (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 struc-
       ture  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 allocated from the memory provided with  the  buffer
       parameter,  which  is bufsize 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(), get-
       grgid(), 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 contain 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 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);
              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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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)