fgetgrent_r

GETGRENT(3)		  Linux Programmer’s Manual		  GETGRENT(3)



NAME
       getgrent_r, fgetgrent_r - get group file entry reentrantly

SYNOPSIS
       #define _GNU_SOURCE
       #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);

DESCRIPTION
       The  functions  getgrent_r()  and fgetgrent_r() are the reentrant ver-
       sions 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 given as parameter.

       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 non-reentrant 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  buffer
       *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.

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

       int main() {
	     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();
	     return 0;
       }

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

	   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.

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



GNU				  2003-11-15			  GETGRENT(3)