getgroups() -- get supplementary group IDs

SYNOPSIS

#include <sys/types.h>

#include <unistd.h>

int getgroups(int gidsetsize, gid_t *grouplist);

DESCRIPTION

The getgroups() function fills in the specified array with the current supplementary group IDs of the calling process.

PARAMETERS

gidsetsize: Specifies the number of elements in the supplied array grouplist. If gidsetsize is zero, getgroups() returns the number of supplementary group IDs associated with the calling process without modifying the array that the grouplist parameter points to.
grouplist: Is the array where getgroups() supplies the supplementary group IDs of the calling process. It returns the actual number of supplementary group IDs stored in the array.

If successful, getgroups() returns the number of supplementary group IDs written to grouplist if gidsetsize is greater than 0, or the number of supplementary group IDs for the process if gidsetsize is 0. On failure, getgroups() returns -1 and sets errno to one of the following values: