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getgrouplist (3)
GETGROUPLIST(3) Linux Programmer's Manual GETGROUPLIST(3)
NAME
getgrouplist - list of groups a user belongs to
SYNOPSIS
#include <grp.h>
int getgrouplist(const char *user, gid_t group,
gid_t *groups, int *ngroups);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getgrouplist(): _BSD_SOURCE
DESCRIPTION
The getgrouplist() function scans the group database for all the groups
user belongs to. Up to *ngroups group IDs corresponding to these
groups are stored in the array groups; the return value from the func-
tion is the number of group IDs actually stored. The group group is
automatically included in the list of groups returned by getgrou-
plist().
RETURN VALUE
If *ngroups is smaller than the total number of groups found, then get-
grouplist() returns -1. In all cases the actual number of groups is
stored in *ngroups.
VERSIONS
This function is present since glibc 2.2.4.
CONFORMING TO
This function is non-standard; it appears on most BSDs.
BUGS
The glibc 2.3.2 implementation of this function is broken: it over-
writes memory when the actual number of groups is larger than *ngroups.
EXAMPLE
/* This crashes with glibc 2.3.2 */
#include <stdio.h>
#include <stdlib.h>
#include <grp.h>
#include <pwd.h>
int
main(void)
{
int i, ng = 0;
char *user = "who"; /* username here */
gid_t *groups = NULL;
struct passwd *pw = getpwnam(user);
if (pw == NULL)
exit(EXIT_SUCCESS);
if (getgrouplist(user, pw->pw_gid, NULL, &ng) < 0) {
groups = (gid_t *) malloc(ng * sizeof (gid_t));
getgrouplist(user, pw->pw_gid, groups, &ng);
}
for (i = 0; i < ng; i++)
printf("%d\n", groups[i]);
exit(EXIT_SUCCESS);
}
SEE ALSO
getgroups(2), setgroups(2)
GNU 2007-07-26 GETGROUPLIST(3)
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