When is called, it creates a single window with a shell in it (or the specified command) and then gets out of your way so that you can use the program as you normally would.
Then, at any time, you can create new (full-screen) windows with other programs in them (including more shells), kill the current window, view a list of the active windows, turn output logging on and off, copy text between windows, view the scrollback history, switch between windows, etc.
See Special Capabilities, for more information about telling Attach here and now.
In detail this means: If a session is running, then reattach. If it was not running create it and notify the user. session, this option sets the default command character.
This is the VT100 style type and perfectly suited for will be content to use it, but updating a character put into the last position on the screen may not be possible until the screen scrolls or the character is moved into a safe position in some other way.
This delay can be shortened by using a terminal with insert-character capability.
12 (or more) indicates that there are 2 (or more) sessions to resume and you should specify which one to choose. The second form is used to connect to another user's screen session which runs in multiuser mode.
A string in single-quotes is also protected from variable substitution.
Two configuration files are shipped as examples with your screen distribution: is not an absolute path and screen is already processing a source command, the parent directory of the running source command file is used to search for the new command file before screen's current directory.
Note that termcap/terminfo/termcapinfo commands only work at startup and reattach time, so they must be reached via the default screenrc files to have an effect. As of version 3.3, all commands can be bound to keys, although some may be less useful than others.
11 (or more) indicates 1 (or more) usable sessions.
In combination with ‘’ the exit value is as follows: 10 indicates that there is no session to resume.