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.\" Copyright 2002 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.\" Distributed under GPL
.\" Thanks to glibc info pages
.\"
.\" Modified 2003-11-18, aeb: glibc is broken
.TH GETGROUPLIST 2 2003-11-18 "GNU" "Linux Programmer's Manual"
.SH NAME
getgrouplist \- list of groups a user belongs to
.SH SYNOPSIS
.sp
.B #include <grp.h>
.sp
.BI "int getgrouplist (const char *" user ", gid_t " group ,
.in 25
.BI "gid_t *" groups ", int *" ngroups );
.SH DESCRIPTION
The
.B getgrouplist()
function scans the group database for all the groups
.I user
belongs to. Up to
.RI * ngroups
group IDs corresponding to these groups are stored in the array
.IR groups ;
the return value from the function is the number of group IDs
actually stored. The group
.I group
is automatically included in the list of groups returned by
.BR getgroup\%list() .
.SH "RETURN VALUE"
If
.RI * ngroups
is smaller than the total number of groups found, then
.B getgrouplist()
returns a value of `-1'.
In all cases the actual number of groups is stored in
.RI * ngroups .
.SH BUGS
The glibc 2.3.2 implementation of this function is broken:
it overwrites memory when the actual number of groups is larger than
.RI * ngroups .
.SH "CONFORMING TO"
This function is present since glibc 2.2.4.
.SH EXAMPLE
.nf
/* 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\en", groups[i]);
return 0;
}
.fi
.SH "SEE ALSO"
.BR getgroups (3),
.BR setgroups (3)
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