SETGROUPS(2)              FreeBSD System Calls Manual             SETGROUPS(2)

NAME
     setgroups - set group access list

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/param.h>
     #include <unistd.h>

     int
     setgroups(int ngroups, const gid_t *gidset);

DESCRIPTION
     The setgroups() system call sets the group access list of the current
     user process according to the array gidset.  The ngroups argument
     indicates the number of entries in the array and must be no more than
     {NGROUPS_MAX}+1.

     Only the super-user may set a new group list.

     The first entry of the group array (gidset[0]) is used as the effective
     group-ID for the process.  This entry is over-written when a setgid
     program is run.  To avoid losing access to the privileges of the
     gidset[0] entry, it should be duplicated later in the group array.  By
     convention, this happens because the group value indicated in the
     password file also appears in /etc/group.  The group value in the
     password file is placed in gidset[0] and that value then gets added a
     second time when the /etc/group file is scanned to create the group set.

RETURN VALUES
     The setgroups() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The setgroups() system call will fail if:

     [EPERM]            The caller is not the super-user.

     [EINVAL]           The number specified in the ngroups argument is larger
                        than the {NGROUPS_MAX}+1 limit.

     [EFAULT]           The address specified for gidset is outside the
                        process address space.

SEE ALSO
     getgroups(2), initgroups(3)

HISTORY
     The setgroups() system call appeared in 4.2BSD.

FreeBSD 13.1-RELEASE-p6        January 19, 2018        FreeBSD 13.1-RELEASE-p6