Overview |
Overview and function of X Windows
- Project Athena
- X Windows was originally developed at MIT, to tackle the problem of distributed computing on a large undergraduate campus
- Windows over the network
- Provides a graphical, windows-like interface to remote machines, and runs over the network
- Centalized computers, decentralized display
- Based on a model involving large central machines (usually UNIX minicomputers), and essentially dumb, but graphics capable
terminals, called X stations or X terminals
- Client-server
- In X Windows, the terms client & server are reversed from their normal usage:
- The X server is the agent performing local screen management
- The X client is the program running on the remote system, whose output will be seen graphically
Clients can run on muliple remote machines, and all display their output back on the same console.
- Stateless
- Client and server do not operate in lock step. Events on the server (the user end) trigger events on the client, but the user can get ahead of
the expected responses, resulting in situations resembling type-ahead.
- X servers
- The X server manages the display at the user workstation. Originally, the X server would run in a dedicated machine called an X station.
There are also X server packages for Macintosh and PC, which allow your Mac or PC to emulate an X terminal.
|
UNIX Connection Methods |
SSH
- Allows login in ASCII (character) mode
- From another UNIX machine, just use the 'ssh' command
- From a PC or Macintosh, you need a ssh client program such as SSH or Putty.
|
X Windows Connection Methods |
Unix to Unix connections
Launch clients from the UNIX command line
- SSH to the host computer, and login in
- From the UNIX command line, set your DISPLAY variable:
export DISPLAY=my.local.pc.uconn.edu:0
where my.local.pc.uconn.edu is the hostname or IP of your workstation. The zero (0) indicates server number 0. You can also indicate the screen number, as in 0:0.
- Lauch clients from the UNIX command prompt:
xclock
Note: If initiating SSH from another UNIX machine, you will first have to authorize the remote host to display
X output on your machine, using the xhost command. Issue this command on your UNIX machine, prior to launching the SSH command:
xhost +remote.machine.uconn.edu
where remote.machine.uconn.edu is the hostname of the machine you want to SSH to.
For connection using Windows or Macs please refer to your third party X Server documentation.
|
Some X Clients |
Editors and debuggers
| Client |
Description |
Directory |
Supports -display flag |
Supports -ls flag |
Required options |
| dtpad |
A text editor, similar to the DOS editor |
/usr/dt/bin |
yes |
yes |
-standAlone |
| emacs |
A popular text editor for UNIX |
/usr/local/bin |
yes |
no |
none |
| xldb |
Debugger for Fortran, C, C++ |
/usr/lpp/xldb/bin |
yes |
no |
Requires the name of an executable file |
System interfaces
| Client |
Description |
Directory |
Supports the -display flag |
Supports the -ls flag |
Required options |
| xman |
Displays man pages, allows forward & backward scrolling |
/usr/bin/X11 |
no |
no |
none; optionally specify the man page |
| info |
InfoExplorer, IBM's library of hypertext documentation on UNIX, AIX software, RS/6000 hardware |
/usr/bin |
yes |
yes |
none; optionally specify alternate libraries with -l flag |
Software packages
| Client |
Description |
Directory |
-display flag |
-ls flag |
Required options |
| sas |
Statistical analysis, graphics |
/usr/local/bin |
yes |
no |
none |
mathe-
matica |
Symbolic math, graphics |
/usr/local/bin |
yes |
no |
none |
| xmaple |
Symbolic math, graphics |
/usr/local/bin |
yes |
no |
need to append /usr/local/bin to PATH |
| xxlf |
X windows interface to the xlf (Fortran) compiler |
/usr/bin/
xlf/xxlf |
yes |
no |
none |
Miscellaneous X clients
| Client |
Description |
Directory |
Supports -display flag |
Supports -ls flag |
Required options |
| gnuplot |
Plotting package |
/usr/local/bin |
yes |
no |
none; optionally specify program file |
| xcalc |
Scientific calculator |
/usr/bin/X11 |
yes |
no |
none |
| xclock |
Display time |
/usr/bin/X11 |
yes |
no |
none |
X defaults
- Most IBM clients have defaults files in /usr/lib/X11/app-defaults
- Common Desktop clients (CDE) have defaults files in /usr/dt/app-defaults/C
- Other packages (e.g. Maple, Mathematica) have their own defaults files; see online help or man page for each package
- User specified defaults can be stored in .Xdefaults in home directory
- IBM provides the custom commmand to modify defaults
|
University of
Connecticut