4.7. Choosing the DISPLAY   

The DISPLAY environment variable is used by the client to find out which server to connect to. ( Your program can specifically request a particular server, but normally will just specify NULL. When this happens, the value of the DISPLAY environment variable is used to determine the server to connect to). The format of the DISPLAY variable is as follows: 


  hostname -  the network name of the machine which is running the

    desired X server, eg lust.

    For TCP/IP networks you can also use the Internet address,

    eg. 134.7.1.5


  special character -  a separator character, usually a colon,

    which indicates what kind of network connection to use.

    One colon indicates ethernet, while two colons indicate DECnet.


  X server # -  the number of the X server on the display node.

    In theory you could have many X servers running.

    In practise, I have not seen this situation.

    Usually you wish to connect to the first server which is number 0,

    eg. lust:0


  screen number -  if the server is controlling more than one screen

    you will need to specify which screen you wish to display on.

    If there is only one screen you do not need to specify this number.

The string before the ":" is significant in the following way: 

if set to               it means

---------               --------

unix (eg. unix:0)       connect using unix domain sockets

hostname (eg. lust:0)   connect using TCP domain sockets

nothing (eg. :0)        connect using fastest transport method

You will find that most vendors will tend to just use the DISPLAY environment variable to determine the display of their applications. This is certainly the case with Sun and Silicon Graphics.