xlax

[See a real screenshot]
[See an ANIMATED screenshot (v2.2)] (may be slow on older machines)

Overview

xlax accepts keyboard input from the user and sends it to multiple X11 windows (usually xterms or other terminal windows). It's an ideal tool for system adminstrators who have to do the same thing on multiple machines, or in multiple directories. It allows the virtual connections to windows to be turned on and off, so that only a subset of current windows are in use (this is shown in the diagram above, where the third and fifth windows in the list are not selected). The user can also assign a different text string to each window which will be sent by clicking on the "Send String" button.

In a typical usage, a user might need to check a few things and run a number of commands on five different machines. After setting up all the windows to work with xlax (see below), and with send strings set to hostnames, the user will type "ssh " and then click "Send String", and then type return, and the user will simultaneously log into those five different machines. They can then type the commands once and see them run on all machines at the same time.

Setting up xlax and windows

In the simplest usage, you start xlax, and then click on the "Add windows" button. You then click on windows that you want xlax to talk to, and click back on the xlax window again when you are done adding. The added windows must have "Allow SendEvents" turned on, or xlax won't be able to talk to them. To set the send string, click on the box to the right of the window name, and enter the string in the popup box. Note that control characters including backspace and carriage return are entered as literal characters so if you make a mistake you have to clear and start over.

This method of setup can be tedious, and xlax also allows for automated setup. If you press the "Find xlax:" button, or if you start xlax with -find, it will search for windows with a Name hint that starts with "xlax:" and add them automatically. Additionally, any text after the "xlax:" will be used as the send string. The "xlax:" prefix can be changed to some other string with the "-prefix" option. For xterms, the name hint is set with the "-name" option. Here's an example:

  example% xterm -xrm 'XTerm*allowSendEvents: true' -name xlax:string1 &
  [1] 555
  example% xterm -xrm 'XTerm*allowSendEvents: true' -name xlax:string2 &
  [2] 556
  example% xterm -xrm 'XTerm*allowSendEvents: true' -name xlax:string3 &
  [3] 557
  example% xlax -find &

While all this is an improvement, it is still tedious to prepare all of the windows with the proper Name hint. The real use for this method is to make window setup script-able, for cases where you repeatedly need the same layout of windows. One such script (mkxlax) is included in this package, and is described below.

mkxlax

mkxlax will create a number of xterms with the send strings preset. The simplest form of using mkxlax is to simply provide a list of send strings:

  mkxlax host1 host2 host3 host4 host5

This command will create 5 xterms, with sendEvents enabled, and with the name hints set to the arguments, e.g. the first window will have a name hint of "mkxlax:host1". mkxlax then starts up "xlax -find -prefix mkxlax", to find all the windows that have been set up.

mkxlax also has options for controlling the positioning of the windows, allowing them to be tiled or stacked, overlapped or not. It also has options for using different xlax prefixes (with "-group") so that you can run multiple mkxlax commands at the same time without interfering with each other.

All of these options can be stored in a configuration file that lets you have simple presets that you can bring up as needed. This can include the list of send strings, but it doesn't have to. The presets can be overridden on the command line. You can then have a quick command like "mkxlax -layout macservers" to bring up all of your mac servers in a particular arrangement on the screen, or run a command "mkxlax -layout stack_vertical host1 host2 host3" to layout an arbitrary set of windows in an arrangement that you've predefined.

mkxlax is further described in a man page included in the distribution.

Security concerns

xlax relies on the X11 sendEvents being allowed in order to work. If your X server is not properly secured, anyone with a connection to your display could send commands to these windows. Of course, if your X server is not secured they could also do the same thing by other means, so in this author's opinion, xlax doesn't add any significant additional security risk.

It does of course multiply your ability to shoot yourself in the foot.

History

xlax was written in 1992 by Frank Adelstein, then at Ohio State University's Computer and Information Sciences Department. From my vague recollections, the idea for the software came from Steve Romig, and the idea for the name came from me. I'm not really sure that last bit is true, but since I don't remember clearly, I can claim anything I like.

xlax was modified by me in 2007 to allow for automatically finding windows based on the name hint. Also added was automatic dropping of dead windows, and an improved interface for manually setting the send string.

A different version of mkxlax was written by me initially in maybe 1998. It was completely rewritten in 2007 to accomodate xlax' ability to automatically find and add windows.

Downloading and Compiling

The Freecode listing replaces Freshmeat.

Pretenders to the Throne

There are a number of other latecomers out there that do similar things to what xlax does. In my opinion, xlax together with mkxlax offers the most complete set of features. I think xlax is the only one with send strings. Plus it has the funniest name. Anyway here is the competition:

keyboardcast is pretty similar in features to xlax. You can add and drop windows interactively, and select and deslect which windows are active at any time. It has a selection mechanism which is similar to xlax' use of the name hint, however I believe keyboardcast uses the window title, which depending on user's set up may end up being changed by the shell to display current directory or whatever. It isn't clear if there's any mechanism for starting a group of windows automatically that are added in.
multixterm is yet another. It looks fairly feature-rich, and is implemented in tcl/tk, and is designed to be easy to modify.
cluster ssh is a project with a program called cssh. More of the same.
BitCluster is a whole collection of tools which include fanout, and xfanout. fanout sends output to multiple terminals, and xfanout manages windows. There's a ctelnet script wich serves to start things up, probably similar to my mkxlax script.
pconsole uses a mechanism that does not require X11, rather it sends input directly to the terminal devices. Because of this it requires root access. It has the odd feature of displaying everything you type (including passwords) in the original pconsole window. Windows can be added and deleted through a command-line interface (you have to know the tty device name of the local terminal, which can be a problem if you've already connected that window to a remote system. Some of the docs imply that pconsole can start pre-connected xterms, but I'm not sure of this.

Two terminal programs apparently have some amount of built-in functionality to do what xlax does. konsole apparently allows you to type into all the tabs of a window at once. This would have the disadvantage that you can only see output from one of those tabbed subwindows. MGT also reportedly has some kind of functionality like this, but I don't know the details.

Non-interactive stuff

There's a number of non-interactive programs out there for remote execution. My own favorite is of course multi-rsh, which can run a single command on dozens or hundreds of systems, in semi-parallel, but with a maximum number of open connections, so you get fast execution without slamming resources.

There's also tentakel, which is quasi-interactive, in that once you have connected to a group of systems, you can run multiple commands, but they are not executed fully interactive.

There's also something called c3, for Cluster Command and Control. And something called fanout, which may be different than the fanout which is available as part of bitcluster.