If you make a typing error while entering a Terminal command, you must correct the error before pressing the Return or Enter key to run the command. Unlike with a word processer, you can’t set the insertion point by clicking in the middle of a command line.
Use the Delete key or press Control-H to erase unwanted characters, and then retype.
To ignore what you have typed and start again, press Control-U.
You can also use the arrow keys to move the insertion point back and forth within the command line. When you start typing, the text appears in the command at the insertion point.