On Tue, 06 Nov 2012 23:08:11 +0000, Prasad, Ramit wrote: > Steven D'Aprano wrote: >> >> On Tue, 06 Nov 2012 17:16:44 +0000, Prasad, Ramit wrote: >> >> >> To enter the newline, I typed Ctrl-Q to tell bash to treat the next >> >> character as a literal, and then typed Ctrl-J to get a newline. >> > >> > That sounds complicated, my version of bash lets me type >> > 'foo<enter>bar'<enter> for the same effect. >> >> Well, I learned something new about bash. >> >> On the other hand, the Ctrl-Q next-char-is-literal trick works for >> entering control characters that otherwise don't have a key on the >> keyboard. >> >> > Would you mind elaborating on how this works? I know it's not a bash > list, but I do not understand how ctrl-J is considered a literal. > Obviously, I must have a different definition of "literal". Where can I > find a list of other literals? My Google-fu is being weak today. :(
I'm not an expert, so the following may not be exactly correct. As I understand it, when you hit a key on the keyboard, it sends the character you typed to the operating system. (The OS can then remap keys, generate keyboard events including a timestamp, etc.) Hit the J key, and the event includes character "j". Hit Shift-J, and character "J" is sent. Hit Ctrl-J, and the character sent is the ASCII control character ^J, or newline. (Technically, the name for ASCII 10 is "linefeed" rather than "newline".) Similarly, other control character combinations send other control codes: ^A = ASCII 0x01 Start Of Heading ^L = ASCII 0xFF Formfeed \f ^M = ASCII 0x0D Carriage Return \r etc. http://en.wikipedia.org/wiki/C0_and_C1_control_codes When readline is enabled in bash, one of the standard editing commands is that C-q (usually ctrl-Q on the keyboard) instructs readline to treat the next key as a literal. So Ctrl-Q followed by Backspace won't delete the previous character, but insert a literal DEL 0x7F character. (One of those historical quirks is that on most(?) keyboards, the Backspace key generates a DEL character rather than the ^H backspace control code, and the Delete key generates an escape sequence. Go figure.) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
