How to copy text from Emacs to another application on Linux

Let’s be careful with our definitions here

• An Emacs copy is the command kill-ring-save (usually bound to M-w).
• A system copy is what you typically get from pressing C-c (or choosing “Edit->Copy” in a application window).
• An X copy is “physically” highlighting text with the mouse cursor.
• An Emacs paste is the command yank (usually bound to C-y).
• A system paste is what you typically get from pressing C-v (or choosing “Edit-Paste” in an application window).
• An X paste is pressing the “center mouse button” (simulated by pressing the left and right mouse buttons together).

In my case (on GNOME):

• Both Emacs and system copy usually work with X paste.
• X copy usually works with Emacs paste.

• To make system copy work with Emacs paste and Emacs copy work with system paste, you need to add (setq x-select-enable-clipboard t) to your .emacs. Or try

  META-X set-variable RET x-select-enable-clipboard RET t
  

I think this is pretty standard modern Unix behavior.

It’s also important to note (though you say you’re using Emacs in a separate window) that when Emacs is running in a console, it is completely divorced from the system and X clipboards: cut and paste in that case is mediated by the terminal. For example, “Edit->Paste” in your terminal window should act exactly as if you typed the text from the clipboard into the Emacs buffer.