DISPLAY Environment Variable

cjhancock · June 30, 2010, 10:18am

I've seen articles which say "export DISPLAY=<IP>:0" and others which say "export DISPLAY=<IP>:0.0". Can someone explain what the difference is?

TIA

fpmurphy · June 30, 2010, 11:18am

From a X(7) man page:

From the user's perspective, every X server has a display name of the form:

hostname:displaynumber.screennumber

This information is used by the application to determine how it should connect to the server and which screen it should use by default (on displays with multiple monitors):

hostname
The hostname specifies the name of the machine to which the display is physically connected. If the hostname is not given, the most efficient way of communicating to a server on the same machine will be used.
displaynumber
The phrase "display" is usually used to refer to collection of monitors that share a common keyboard and pointer (mouse, tablet, etc.). Most workstations tend to only have one keyboard, and therefore, only one display. Larger, multi-user systems, however, frequently have several displays so that more than one person can be doing graphics work at once. To avoid confusion, each display on a machine is assigned a display number (beginning at 0) when the X server for that display is started. The display number must always be given in a display name.
screennumber
Some displays share a single keyboard and pointer among two or more monitors. Since each monitor has its own set of windows, each screen is assigned a screen number (beginning at 0) when the X server for that display is started. If the screen number is not given, screen 0 will be used.

Note that an IP address can be used instead of a hostname.

mewbie · June 30, 2010, 11:25pm

Hope it's ok to join in on an environment variable question-
How to view what environment variables users have set up?
env bob doesn't work, cd'ing to their home dir and running the cmd doesn't work either.
( I know to see my own it's: env)
Thank you

kduffin · June 30, 2010, 11:39pm

If you have root rights, you can simply su - to the user and run env. Alternatively, you could just source their respective .chsrc, .bashrc etc. ( . /path/to/user/.bashrc) and then check the environment differences are. What's the purpose of your particular investigation?

Cheers,

Keith

mewbie · July 1, 2010, 1:30am

Thank you for the reply kduffin
That works great- with the exception that the next time the user logs in they will see 'Last login' as my IP - not their own and their .bash_history will contain cmds I executed.
It is also quiet a few steps to yield the results of 'env' for all users.
Is there another method to view one or all users env variables?
For example to view if any users have messed around with their history? such as 'unset HISTFILE'.
I know how to prevent them from altering it, I just want to know if they have .