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 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,
       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)