xscreensaver(1) has a client-server model: the xscreensaver process is a daemon that runs in the background; it is controlled by other foreground programs such as xscreensaver-command and xscreensaver-demo(1).

This program, xscreensaver-command, is a command-line-oriented tool; the xscreensaver-demo(1). program is a graphical tool.

-help

Prints a brief summary of command-line options.

-demo

This just launches the xscreensaver-demo(1) program, in which one can experiment with the various graphics hacks available, and edit parameters.

-demo number

When the -demo option is followed by an integer, it instructs the xscreensaver daemon to run that hack, and wait for the user to click the mouse before deactivating (i.e., mouse motion does not deactivate.) This is the mechanism by which xscreensaver-demo(1) communicates with the xscreensaver(1) daemon. (The first hack in the list is numbered 1, not 0.)

-prefs

Like the no-argument form of -demo, but brings up that program's Preferences panel by default.

-activate

Tell xscreensaver to turn on immediately (that is, blank the screen, as if the user had been idle for long enough.) The screensaver will deactivate as soon as there is any user activity, as usual.

It is useful to run this from a menu; you may wish to run it as

sleep 5 ; xscreensaver-command -activate

to be sure that you have time to take your hand off the mouse before the screensaver comes on. (Because if you jiggle the mouse, xscreensaver will notice, and deactivate.)

-deactivate

This tells xscreensaver to pretend that there has just been user activity. This means that if the screensaver is active (the screen is blanked), then this command will cause the screen to un-blank as if there had been keyboard or mouse activity. If the screen is locked, then the password dialog will pop up first, as usual. If the screen is not blanked, then this simulated user activity will re-start the countdown (so, issuing the -deactivate command periodically is one way to prevent the screen from blanking.)

-cycle

If the screensaver is active (the screen is blanked), then stop the current graphics demo and run a new one (chosen randomly.)

-next

This is like either -activate or -cycle, depending on which is more appropriate, except that the graphics hack that will be run is the next one in the list, instead of a randomly-chosen one. In other words, repeatedly executing -next will cause the xscreensaver process to invoke each graphics demo sequentially. (Though using the -demo option is probably an easier way to accomplish that.)

-prev

This is like -next, but cycles in the other direction.

-select number

Like -activate, but runs the Nth element in the list of hacks. By knowing what is in the programs list, and in what order, you can use this to activate the screensaver with a particular graphics demo. (The first element in the list is numbered 1, not 0.)

-exit

Causes the xscreensaver process to exit gracefully. This does nothing if the display is currently locked.

Warning: never use kill -9 with xscreensaver while the screensaver is active. If you are using a virtual root window manager, that can leave things in an inconsistent state, and you may need to restart your window manager to repair the damage.

-lock

Tells the running xscreensaver process to lock the screen immediately. This is like -activate, but forces locking as well, even if locking is not the default (that is, even if xscreensaver's lock resource is false, and even if the lockTimeout resource is non-zero.)

Note that locking doesn't work unless the xscreensaver process is running as you. See xscreensaver(1) for details.

-version

Prints the version of xscreensaver that is currently running on the display: that is, the actual version number of the running xscreensaver background process, rather than the version number of xscreensaver-command. (To see the version number of xscreensaver-command itself, use the -help option.)

-time

Prints the time at which the screensaver last activated or deactivated (roughly, how long the user has been idle or non-idle: but not quite, since it only tells you when the screen became blanked or un-blanked.)

-restart

Causes the screensaver process to exit and then restart with the same command line arguments as last time. Do this after you've changed the resource database, to cause xscreensaver to notice the changes.

Warning: if you have a .xscreensaver file, this might not do what you expect. You're probably better off killing the existing xscreensaver (with xscreensaver-command -exit) and then launching it again.

The important point is, you need to make sure that the xscreensaver process is running as you. If it's not, it won't be reading the right .xscreensaver file.

-watch

Prints a line each time the screensaver changes state: when the screen blanks, locks, unblanks, or when the running hack is changed. This option never returns; it is intended for use by shell scripts that want to react to the screensaver in some way. An example of its output would be:

BLANK Fri Nov  5 01:57:22 1999
RUN 34
RUN 79
RUN 16
LOCK Fri Nov  5 01:57:22 1999
RUN 76
RUN 12
UNBLANK Fri Nov  5 02:05:59 1999

The above shows the screensaver activating, running three different hacks, then locking (perhaps because the lock-timeout went off) then unblanking (because the user became active, and typed the correct password.) The hack numbers are their index in the `programs' list (starting with 1, not 0, as for the -select command.)

For example, suppose you want to run a program that turns down the volume on your machine when the screen blanks, and turns it back up when the screen un-blanks. You could do that by running a Perl program like the following in the background. The following program tracks the output of the -watch command and reacts accordingly:

#!/usr/bin/perl

my $blanked = 0;
open (IN, "xscreensaver-command -watch |");
while (<IN>) {
    if (m/^(BLANK|LOCK)/) {
        if (!$blanked) {
            system "sound-off";
            $blanked = 1;
        }
    } elsif (m/^UNBLANK/) {
        system "sound-on";
        $blanked = 0;
    }
}

Note that LOCK might come either with or without a preceding BLANK (depending on whether the lock-timeout is non-zero), so the above program keeps track of both of them.

xset dpms force off

See the xset(1) manual for more info.

You can also use xscreensaver-demo(1) to make the monitor power down after a few hours, meaning that xscreensaver will run graphics until it has been idle for the length of time you specified; and after that, the monitor will power off, and screen hacks will stop being run.

DISPLAY

to get the host and display number of the screen whose saver is to be manipulated.

PATH

to find the executable to restart (for the -restart command). Note that this variable is consulted in the environment of the xscreensaver process, not the xscreensaver-command process.

Please let me know if you find any bugs or make any improvements.