getgroups(2)
Name
getgroups − get group access list
Syntax
#include <sys/types.h>
#include <unistd.h>
int getgroups(gidsetsize, grouplist)
int gidsetsize;
int grouplist[];
Description
The getgroups call gets the current group access list of the user process and stores it in the array of int grouplist. The gidsetsize parameter indicates the number of entries that can be placed in grouplist.
Return Values
Upon success, the call returns the number of groups as the value of the function. No more than NGROUPS, as defined in <sys/param.h>, are returned.
A value of −1 indicates that an error occurred, and the error code is stored in the global variable, errno.
Diagnostics
The getgroups call fails under the following conditions:
[EINVAL] The gidsetsize argument is smaller than the number of groups in the group set.
[EFAULT] The grouplist argument specifies invalid addresses.
Environment
POSIX
When your program is compiled in the POSIX environment, the grouplist argument should be defined as follows: gid_tgrouplist[];
Additionally, in the POSIX environment, if the gidsetsize argument is zero, getgroups returns the number of supplemental group IDs associated with the calling process, without modifying the array pointed to by the grouplist argument.