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); |
![[Note]](../stylesheet/note.png) |
Note | ||||
|---|---|---|---|---|---|
|
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 given as parameter.
The group structure is
defined in <grp.h> as
follows:
struct group { char * gr_name;char * gr_passwd;gid_t gr_gid;char ** gr_mem;};
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.
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);
}
COLOPHON
This page is part of release 2.79 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/.
|
Copyright (c) 2003 Andries Brouwer (aebcwi.nl) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatting or typesetting system, including intermediate and printed output. This manual is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this manual; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA. |