GETGRENT_R
GETGRENT_R
NAMESYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
CONFORMING TO
NOTES
EXAMPLE
SEE ALSO
COLOPHON
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 */
};
For more information about the fields of this structure, see group(5).
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 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 411toppm(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 3.69 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man−pages/.
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