On bash command-line, how to delete all letters before cursor?

Ctrl-u – Cut everything before the cursor

Other Bash shortcuts,

• Ctrl-a Move cursor to beginning of line
• Ctrl-e Move cursor to end of line
• Ctrl-b Move cursor back one word
• Ctrl-f Move cursor forward one word
• Ctrl-w Cut the last word
• Ctrl-k Cut everything after the cursor
• Ctrl-y Paste the last thing to be cut
• Ctrl-_ Undo

And discover more via man page for bash shell: man bash

Additional bash command-line shortcut cheat sheet: http://www.bigsmoke.us/readline/shortcuts

See the documentation here: http://www.gnu.org/software/bash/manual/bashref.html#Commands-For-Killing

Obligatory: Learn more about Bash, Linux, and Tech through Julia’s comics: https://twitter.com/b0rk/media