when running a command that's reading what you're typing to stdin, you press Ctrl-D to tell it that you're done. Because, as your "man ascii" trick shows, this

when running a command that's reading what you're typing to stdin, you press Ctrl-D to tell it that you're done. Because, as your "man ascii" trick shows, this generates the "end of transmission" character. This is slightly different than being able to actually generate those characters as input. If you put a control-d in a file, nothing will stop reading the file when it sees the control-d, it's just another byte. readline knows how to interpret a bunch of control characters. There's also the terminal driver that has interpretations, which you can see with `stty -a`. When the tty layer sees a control-d or a control-c, it closes stdin or generates SIGINT, respectively. But even this can be dependent on if you're on a pty or attached directly to a serial line. There's nothing special about the mapping of control-d to end-of-transmission character, that's just how the layer that sees it is interpreting it. You can, for example, change how control-c is interpreted by `stty intr ^B`, which will make control-b generate SIGINT. And there's a way to put the terminal driver in complete transparent/passthru mode.