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.Dd January 19, 2018 .Dt SETGROUPS 2 .Os .Sh NAME .Nm setgroups .Nd set group access list .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/param.h n unistd.h .Ft int .Fn setgroups "int ngroups" "const gid_t *gidset" .Sh DESCRIPTION The .Fn setgroups system call sets the group access list of the current user process according to the array .Fa gidset . The .Fa ngroups argument indicates the number of entries in the array and must be no more than .Dv {NGROUPS_MAX}+1 .
p Only the super-user may set a new group list.
p The first entry of the group array
q Va 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 .Va 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
a /etc/group . The group value in the password file is placed in .Va gidset[0] and that value then gets added a second time when the
a /etc/group file is scanned to create the group set. .Sh RETURN VALUES .Rv -std setgroups .Sh ERRORS The .Fn setgroups system call will fail if: l -tag -width Er t Bq Er EPERM The caller is not the super-user. t Bq Er EINVAL The number specified in the .Fa ngroups argument is larger than the .Dv {NGROUPS_MAX}+1 limit. t Bq Er EFAULT The address specified for .Fa gidset is outside the process address space. .El .Sh SEE ALSO .Xr getgroups 2 , .Xr initgroups 3 .Sh HISTORY The .Fn setgroups system call appeared in x 4.2 .