NAME

     getgroups — get group access list

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     getgroups(int gidsetlen, gid_t *gidset);

DESCRIPTION

     The getgroups() system call gets the current group access list of the user process and
     stores it in the array gidset.  The gidsetlen argument indicates the number of entries that
     may be placed in gidset.  The getgroups() system call returns the actual number of groups
     returned in gidset.  At least one and as many as {NGROUPS_MAX}+1 values may be returned.  If
     gidsetlen is zero, getgroups() returns the number of supplementary group IDs associated with
     the calling process without modifying the array pointed to by gidset.

     The value of {NGROUPS_MAX} should be obtained using sysconf(3) to avoid hard-coding it into
     the executable.

RETURN VALUES

     A successful call returns the number of groups in the group set.  A value of -1 indicates
     that an error occurred, and the error code is stored in the global variable errno.

ERRORS

     The possible errors for getgroups() are:

     [EINVAL]           The argument gidsetlen is smaller than the number of groups in the group
                        set.

     [EFAULT]           The argument gidset specifies an invalid address.

SEE ALSO

     setgroups(2), initgroups(3), sysconf(3)

STANDARDS

     The getgroups() system call conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

HISTORY

     The getgroups() system call appeared in 4.2BSD.