Intro
Screen is a text-based program usually described as a window manager or terminal multiplexer. While it does a great many things, its two biggest features are its detachability and its multiplexing. The detachability means that you can run programs from within screen, detach and logout, then log in later, reattach, and the programs will still be there. The multiplexing means that you can have multiple programs running within a single screen session, each within its own window. You can display multiple windows at once, or just switch between them, even if you only have a single terminal window to use.
For more info on what screen can do, see the detailed description.
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FAQ
First stop for any questions should be the FAQ.
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Where to Get It
The official GNU screen page is http://www.gnu.org/software/screen/. The canonical repository for the screen source is ftp://ftp.gnu.org/gnu/screen/. There are no official precompiled binaries, but your system vendor may have them available.
The current development sources may also be had from the git repository; or you may browse them online. Note that building from the repository sources may require additional tools, such as GNU Autoconf.
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Discussion
The user discussion mailing list can be found at http://lists.gnu.org/mailman/listinfo/screen-users. There is an IRC channel on Freenode (irc.freenode.net) named #screen.
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Bugs
See the bugtracker page for information on submitting or searching for bug reports regarding GNU Screen. If you're unsure whether something is a bug, feel free to ask about it on the mailing lists or in the IRC channel.
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Terminology
Like many complex things, screen has its own terminology. Knowing it is useful when discussing screen.