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 .