GETGRENT_R(3)                                       Linux Programmer's Manual                                      GETGRENT_R(3)



NAME
       getgrent_r, fgetgrent_r - get group file entry reentrantly

SYNOPSIS
       #include <grp.h>

       int getgrent_r(struct group *gbuf, char *buf,
                      size_t buflen, struct group **gbufp);

       int fgetgrent_r(FILE *fp, struct group *gbuf, char *buf,
                       size_t buflen, struct group **gbufp);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getgrent_r(): _GNU_SOURCE
       fgetgrent_r(): _SVID_SOURCE

DESCRIPTION
       The  functions  getgrent_r()  and  fgetgrent_r()  are the reentrant versions of getgrent(3) and fgetgrent(3).  The former
       reads the next group entry from the stream initialized by setgrent(3).  The latter reads the next group  entry  from  the
       stream fp.

       The group structure is defined in <grp.h> as follows:

           struct group {
               char    *gr_name;     /* group name */
               char    *gr_passwd;   /* group password */
               gid_t    gr_gid;      /* group ID */
               char   **gr_mem;      /* group members */
           };

       The  nonreentrant  functions  return  a pointer to static storage, where this static storage contains further pointers to
       group name, password and members.  The reentrant functions described here return all of that in caller-provided  buffers.
       First of all there is the buffer gbuf that can hold a struct group.  And next the buffer buf of size buflen that can hold
       additional strings.  The result of these functions, the struct group read from the stream, is stored in the provided buf-
       fer *gbuf, and a pointer to this struct group is returned in *gbufp.

RETURN VALUE
       On  success,  these  functions return 0 and *gbufp is a pointer to the struct group.  On error, these functions return an
       error value and *gbufp is NULL.

ERRORS
       ENOENT No more entries.

       ERANGE Insufficient buffer space supplied.  Try again with larger buffer.

CONFORMING TO
       These functions are GNU extensions, done in a style resembling the POSIX version of functions like getpwnam_r(3).   Other
       systems use prototype

           struct group *getgrent_r(struct group *grp, char *buf,
                                    int buflen);

       or, better,

           int getgrent_r(struct group *grp, char *buf, int buflen,
                          FILE **gr_fp);

NOTES
       The  function  getgrent_r()  is  not  really  reentrant since it shares the reading position in the stream with all other
       threads.

EXAMPLE
       #define _GNU_SOURCE
       #include <grp.h>
       #include <stdio.h>
       #include <stdlib.h>
       #define BUFLEN 4096

       int
       main(void)
       {
           struct group grp, *grpp;
           char buf[BUFLEN];
           int i;

           setgrent();
           while (1) {
               i = getgrent_r(&grp, buf, BUFLEN, &grpp);
               if (i)
                   break;
               printf("%s (%d):", grpp->gr_name, grpp->gr_gid);
               for (i = 0; ; i++) {
                   if (grpp->gr_mem[i] == NULL)
                       break;
                   printf(" %s", grpp->gr_mem[i]);
               }
               printf("\n");
           }
           endgrent();
           exit(EXIT_SUCCESS);
       }

SEE ALSO
       fgetgrent(3), getgrent(3), getgrgid(3), getgrnam(3), putgrent(3), group(5)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



GNU                                                        2007-07-26                                              GETGRENT_R(3)