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I have a graphical machine of rhel7, when i run who command , one of the outputs in 2nd column is ':0'. What does ':0' mean ?

marked as duplicate by X Tian, Ulrich Schwarz, dhag, muru, vonbrand Oct 15 '15 at 18:38

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It is the value used by X Windows system to direct the display traffic in your machine. It has the following format:


empty hostname is localhost. D is the sequence number and 0 means only one display in your system. There could also be S number which is the screen number. A display can have more than one screen. But usually there's only one screen and its number is 0 (the default). So in your case the traffic is directed to local host and the only display you have.


If you read the man page for who it tells you that most of the documentation is available as a Textinfo manual and that:

info coreutils 'who invocation'

will display it. An extract of that documentation is:

If given no non-option arguments, 'who' prints the following information for each user currently logged on: login name, terminal line, login time, and remote hostname or X display.

Therefore, the :0 is the X display in use.

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