NAME
getgrouplist - list of groups a user belongs to
SYNOPSIS
#include <grp.h>
I int getgrouplist(const char * user , gid_t group ,
I gid_t * groups , int * ngroups );
DESCRIPTION
The
R 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
R groups ;
the return value from the function is the number of group IDs
actually stored.
The group
group
is automatically included in the list of groups returned by
R getgrouplist ().
RETURN VALUE
If
*ngroups
is smaller than the total number of groups found, then
R getgrouplist ()
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 overwrites 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
