--- a/update-schlittermann-ssh-keys.pl	Wed Aug 12 19:00:32 2015 +0200
+++ b/update-schlittermann-ssh-keys.pl	Wed Aug 12 19:15:33 2015 +0200
@@ -18,7 +18,7 @@
 my $opt_help      = 0;
 my $opt_man       = 0;
 my $opt_keys_dir  = "/usr/share/schlittermann-ssh-keys";
-my $opt_force     = 0;
+my $opt_force     = not -t 0;
 
 my $SSHD_CONF       = "/etc/ssh/sshd_config";
 my $KEYS_DIR        = undef;                              # set later