getgroups(2) BSD System Calls Manual getgroups(2)
NAME
getgroups -- get group access list
SYNOPSIS
#include <unistd.h>
int
getgroups(int gidsetsize, gid_t grouplist[]);
DESCRIPTION
getgroups() gets the current group access list of the current user
process and stores it in the array grouplist[]. The parameter gidsetsize
indicates the number of entries that may be placed in grouplist[].
getgroups() returns the actual number of groups returned in grouplist[].
However, no more than {NGROUPS_MAX} will be returned. If gidsetsize is 0,
getgroups() returns the number of groups without modifying the
grouplist[] array.
Calling initgroups(3) to opt-in for supplementary groups will cause
getgroups() to return a single entry, the GID that was passed to
initgroups(3).
To provide compatibility with applications that use getgroups() in envi-
ronments where users may be in more than {NGROUPS_MAX} groups, a variant
of getgroups(), obtained when compiling with either the macros
_DARWIN_UNLIMITED_GETGROUPS or _DARWIN_C_SOURCE defined, can be used that
is not limited to {NGROUPS_MAX} groups. However, this variant only
returns the user's default group access list and not the group list modi-
fied by a call to setgroups(2) (either in the current process or an
ancestor process). Use of setgroups(2) is highly discouraged, and there
is no foolproof way to determine if it has been previously called.
RETURN VALUES
A successful call returns the number of groups in the group set. Other-
wise, a value of -1 is returned and the global integer variable errno is
set to indicate the error.
ERRORS
The possible errors for getgroups() are:
[EFAULT] The argument grouplist specifies an invalid address.
[EINVAL] The argument gidsetsize, although non-zero, is smaller
than the number of groups in the group set.
LEGACY SYNOPSIS
#include <sys/param.h>
#include <sys/types.h>
#include <unistd.h>
The include files <sys/param.h> and <sys/types.h> are necessary.
SEE ALSO
setgroups(2), initgroups(3), compat(5)
HISTORY
The getgroups() function call appeared in 4.2BSD.
4.2 Berkeley Distribution October 28, 2011 4.2 Berkeley Distribution
Mac OS X 10.9.1 - Generated Mon Jan 6 05:37:07 CST 2014