GETGROUPLIST(3) Linux Programmer's Manual GETGROUPLIST(3)NAMEgetgrouplist - list of groups a user belongs to
SYNOPSIS
#include <grp.h>
int getgrouplist (const char *user, gid_t group,
gid_t *groups, int *ngroups);
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 a value of `-1'. In all cases the actual number of
groups is stored in *ngroups.
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.
CONFORMING TO
This function is non-standard; it appears on most BSDs.
VERSIONS
This function is present since glibc 2.2.4.
EXAMPLE
/* This crashes with glibc 2.3.2 */
#include <stdio.h>
#include <stdlib.h>
#include <grp.h>
#include <pwd.h>
int main() {
int i, ng = 0;
char *user = "who"; /* username here */
gid_t *groups = NULL;
struct passwd *pw = getpwnam(user);
if (pw == NULL)
return 0;
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]);
return 0;
}
SEE ALSOgetgroups(3), setgroups(3)GNU 2003-11-18 GETGROUPLIST(3)