64 lines
2.5 KiB
HTML
64 lines
2.5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>Remote X Apps mini-HOWTO: A Little Theory</TITLE>
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<LINK HREF="Remote-X-Apps-5.html" REL=next>
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<LINK HREF="Remote-X-Apps-3.html" REL=previous>
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<LINK HREF="Remote-X-Apps.html#toc4" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="Remote-X-Apps-5.html">Next</A>
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<A HREF="Remote-X-Apps-3.html">Previous</A>
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<A HREF="Remote-X-Apps.html#toc4">Contents</A>
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<HR>
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<H2><A NAME="s4">4. A Little Theory</A></H2>
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<P>The magic word is <CODE>DISPLAY</CODE>. In the X window system, a display consists
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(simplified) of a keyboard, a mouse and a screen. A display is managed
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by a server program, known as an X server. The server serves displaying
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capabilities to other programs that connect to it.
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<P>A display is indicated with a name, for instance:
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<P>
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<UL>
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<LI> <CODE>DISPLAY=light.uni.verse:0</CODE>
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</LI>
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<LI> <CODE>DISPLAY=localhost:4</CODE>
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</LI>
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<LI> <CODE>DISPLAY=:0</CODE>
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</LI>
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</UL>
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<P>The display consists of a hostname (such as <CODE>light.uni.verse</CODE> and
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<CODE>localhost</CODE>), a colon (<CODE>:</CODE>), and a sequence number (such as <CODE>0</CODE>
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and <CODE>4</CODE>). The hostname of the display is the name of the computer
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where the X server runs. An omitted hostname means the local host. The
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sequence number is usually 0 -- it can be varied if there are multiple
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displays connected to one computer.
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<P>If you ever come across a display indication with an extra <CODE>.n</CODE>
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attached to it, that's the screen number. A display can actually have
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multiple screens. Usually there's only one screen though, with number
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<CODE>n=0</CODE>, so that's the default.
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<P>Other forms of <CODE>DISPLAY</CODE> exist, but the above will do for our purposes.
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<P>For the technically curious:
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<UL>
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<LI> <CODE>hostname:D.S</CODE> means screen <CODE>S</CODE> on display <CODE>D</CODE> of host
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<CODE>hostname</CODE>; the X server for this display is listening at TCP
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port <CODE>6000+D</CODE>.
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</LI>
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<LI> <CODE>host/unix:D.S</CODE> means screen <CODE>S</CODE> on display <CODE>D</CODE>
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of host <CODE>host</CODE>; the X server for this display is listening
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at UNIX domain socket <CODE>/tmp/.X11-unix/XD</CODE> (so it's only
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reachable from <CODE>host</CODE>).
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</LI>
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<LI> <CODE>:D.S</CODE> is equivalent to <CODE>host/unix:D.S</CODE>, where <CODE>host</CODE>
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is the local hostname.
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</LI>
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</UL>
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<P>
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<HR>
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<A HREF="Remote-X-Apps-5.html">Next</A>
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<A HREF="Remote-X-Apps-3.html">Previous</A>
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<A HREF="Remote-X-Apps.html#toc4">Contents</A>
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</BODY>
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</HTML>
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