Ctrl+L in terminal

I accidentally typed ctrl + L in terminal and my terminal window jumped one 'screenful' size. I looked at the keyboard shortcuts in "Edit"->"Keyboard shortcuts" and didn't find that shortcut.

What does ctrl + L do and where is it defined?

Solution 1:

ctrl + L just clear the terminal screen.

It is the keyboard shortcut equivalent of the command clear -x. ^ref

It is property of bash, so you did not found it under keyboard shortcuts in your gnome-terminal. From man bash:

clear-screen (C-l)
          Clear the screen leaving the current line  at  the  top  of  the
          screen.   With  an  argument,  refresh  the current line without
          clearing the screen.

See a detail list of Bash Keyboard Shortcuts.

Solution 2:

If the shell you're using is not intercepting it, you are typing a "Form-feed" character in your terminal. If the terminal application does not intercept or use the keystroke in some way, Ctrl+Letter is translated to the ASCII code of the letter minus 64(1). 65 is the ASCII code of 'A', 'L' is the 12th letter -> code 76. If the shell does not know what to do of the code, it prints it.

Printing a FF char resulted in a new page on a line printer and a clear screen on the terminal (yes, I used a VT-52 back then, at 300 baud).

So Ctrl+L is 12 which is FF. In the same way, Ctrl+I is a TAB, and Ctrl+G rings the bell --- if the terminal or the shell does not intercept it, like Ctrl+C for example.

Notice from the other answer: it seems that bash do intercept CTRL-L and do a clear. Nice touch that the bash authors associated the key with a command which will do more or less the same that the ASCII code did on old terminals!

On the other hand, in my zsh the combination CTRL-I works as TAB and CTRL-H as a Backspace(2).

Old nice ASCII... (notice that letter L is at column 4, row 12, it has ASCII code 4*16+12=76).

Original Image here, from wikipedia article on ASCII.

(1) Ctrl really used to clear the bit 7.

(2) this is the source of the "fail to remove word" joke you sometime find like for example "this was a bad^H^H^Hnot so nice idea"... (with normally a word stronger than bad!)