Useful Things You Can Do with FVWM

Learn how to take screenshots quickly, change window titles and reconfigure a running FVWM instance.
Reconfiguring a Running FVWM Instance

Sometimes one wants to temporarily reconfigure FVWM, perhaps to test the effect of some configuration command. One way to do this is to modify the config file and then restart FVWM. You probably will find, depending, of course, on how your FVWM is configured, that if you click on the root window, you get a menu containing the option Restart FVWM. This is a little tedious, however. Maneuvering the mouse to the root window, clicking on it and choosing the option to restart FVWM takes time, particularly if the root window is completely obscured by windows. And the restart of FVWM takes a significant fraction of a second. There's a better and faster way--the program FvwmCommand, which comes packaged with FVWM.

FvwmCommand can perform a number of functions. We're only interested in one function, however: sending commands to FVWM. Sending commands is a simple task: one simply runs FvwmCommand command_to_send. For example, the command to restart FVWM is called Restart, so to restart FVWM, one only need give the command FvwmCommand Restart at the shell prompt.

In order for FvwmCommand to work, it needs to talk to FVWM. It doesn't do so directly, however; instead, it does so through an intermediary, called FvwmCommandS. FvwmCommandS is an FVWM module, which is a program started by FVWM that communicates with it by means of a special protocol.

The best way to get FVWM to start FvwmCommandS is to put a command to this effect in FVWM's config file. The command to use is Module, and it takes as its argument the name of the module to start. So in this case, the full command is Module FvwmCommandS. Once you've put this command into the FVWM config file and restarted FVWM, you should find that FvwmCommand works for you.

Ronan McGoran is a UNIX system administrator. His home page can be found here.



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Useful Things You Can Do with FVWM

Thomas Adam's picture

Not a bad article on the whole. :) My only gripe with it is that you seem to ignore Fvwm's internal functionality in favour of using superfluous external shell-scripts. Why? For instance, you could use Fvwm{Script,Form} to do all of the preconfigurations easily enough. Not to mention this is the whole reason "PipeRead" exists.

Your title change of window is slightly OTT as well. It would be better to outline the power of Fvwm by actually using its features rather than showing us how good it is to call external scripts. One trick that you can do to title windows:

AddToFunc TitleMeDifferently
+ I ThisWindow ($0) PipeRead 'echo exec xprop -id $[] -set WM_NAME \"$1\"'

Then you can use:

TitleMeDifferently xterm somenewtitle

FVWM for Artists

Anonymous's picture

FVWM can be set up with multiple desktops and zero edge resistance so that an aquired graphic can be stretched across as many desktops as required so that one aquired dot or one print out dot equals one screen pixel.
The results of modifying edges and shading can be seen on a real looking picture as it would appear in the output.

Nice, but what's with all the shell scripts?

Paul Smith's picture

FVWM has a number of modules, including things like FvwmForm which give you a very simple-to-use graphical form generator, that is much nicer for asking users for input than popping an xterm/rxvt and asking from the shell. Someone else commented on starting a new xterm on a remote system; as an example of using FvwmForm I show one I use to do this:

$ cat ~/.fvwm/XTermForm
# -*-fvwm-*-
# This is an FvwmForm definition file for creating specific xterms

DestroyModuleConfig XTermForm*

*XTermForm: WarpPointer

*XTermForm: Line center
*XTermForm: Text "Create New XTerm"
*XTermForm: Line left
*XTermForm: Text "Username:"
*XTermForm: Input UserName 12 "psmith"
*XTermForm: Line left
*XTermForm: Text "Login to host:"
*XTermForm: Input HostName 32 "localhost"
*XTermForm: Line left
*XTermForm: Text "Start on host:"
*XTermForm: Selection LocalSel single
*XTermForm: Choice Local Local on "Local"
*XTermForm: Choice Remote Remote off "Remote"
*XTermForm: Line expand
*XTermForm: Button quit "Create" ^M
*XTermForm: Command Exec rterm -l $(UserName) $(Remote?-r) $(HostName)
*XTermForm: Button restart "Clear"
*XTermForm: Button quit "Cancel" ^[
*XTermForm: Command Nop

Then in one of my menus I have:

+ "%menu/terminal.xpm%XTerm" Module FvwmForm XTermForm

(the stuff between the %...% in the menu title is the name of an icon to put in the menu.)

The rterm mentioned above is a script I wrote that handles creating terminals remotely (with DISPLAY set to my local host) or locally (then logging in within the xterm), with different users, etc. It's sort of customized to my environment so I won't include it but it should be straightforward to write your own, or you can simplify things by leaving out the local/remote option altogether.

I actually have a bunch of these forms for different kinds of things; it really helps create a more integrated desktop.

Or, if you're using Gnome with FVWM you can invoke zenity (see the man page) from your shell script to get a GTK dialog which looks nice. I'm sure KDE has something similar.

And there is another, even more powerful FVWM module for this kind of thing called FvwmScript; I've not used that one though.

rxvt is used so user has favourite editor available

The author's picture

Hi Paul. The reason for popping up a terminal
emulator, rather than using FvwmForm or any other
graphical dialog program, is that I want to give
the user the opportunity to use their favourite
text editor. I know that I'm much faster with
vi than I would be with FvwmForm.

Besides, hardened command-line junkies like me
regard GUIs as a necessary evil, and choose
atavistic command-line solutions whenever

xwd vs import

tjw's picture

I've found that ImageMagick's import utility is in most cases better at capturing screenshots than xwd. xwd often has troubles with windows such as media players, rdesktop, and emulators.

The equivalent of:

xwd -id $w -out /tmp/screenshot && convert /tmp/screenshot /tmp/screenshot.jpg


import -window $w /tmp/screenshot.jpg

Two additional tricks

Anonymous's picture

Two additional tricks I've found useful:

1) create a root window menu item that opens a new xterm connected to a remote host. This requires setting up SSH to support X11 forwarding and using RSA keys so you don't have to use a password.


+ "chaos" Exec /usr/bin/ssh -X -f "/usr/bin/X11/xterm -T chaos"

You should only use this with trusted systems, but it can be a real timesaver since you can then easily launch any remote X application.

2) set up a dynamic background image that indicates system load. Many people find this annoying, but I've found it useful (in those rare occasions when the desktop isn't wallpapered by windows) since it provides some visual feedback when the system is overloaded.


+ "I" Exec /usr/X11R6/bin/xlock -inroot -mode qix &

If this is too busy you could use xearth, xfishtank, or any other screensaver that can be run on the root window.

This has one other cute "feature" - it tends to blow away Windows users. :-)

xscreensaver hacks

Anonymous's picture

All of the xscreensaver display modes, or "hacks", are separate programs that you can use to animate your desktop background by running with the -root command-line option. Each xscreensaver hack has its own man page, so if you want a slow-motion desktop pattern, check the man page for a speed or "-cycle-delay" option.