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 (con-
       sult 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 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(), getgrgid(), or  get-
       grnam().

       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, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                  GETGRGID(3P)