Text files and editors: vi

vi (short for ``visual'') is a very powerful text editor, but takes a lot of getting used to. It works in two modes: command mode and edit mode. In command mode you can delete lines, search (and replace), move to different parts of the file and so on. In edit mode you can type and delete text. vi has a steep learning curve because it is not like many other text editors, but once you get the hang of it you can edit files very quickly.

When you start vi it starts in command mode and will fill the whole terminal window. If the file you are editting doesn't have enough lines to fill the window, non-existent lines are indicated by a tilde ` '.

Probably the most important things you need to know to use vi are:

• Moving the cursor one space
  Originally the cursor was moved by j (down), k (up), h left and l right. On modern vi variants you can also move the cursor with the arrow keys.
• Moving the cursor one word
  w moves the cursor one word forwards (i.e. right), and b moves it one word back.
• Deleting a character
  x deletes the character under the cursor.
• Replacing a character
  r replaces the character under the cursor with whatever character you type next.
• Deleting a line
  dd deletes the entire line the cursor is on.
• Deleting several lines
  d3, followed by the enter key, deletes the current line and the following 3 lines. Of course you can change 3 to any number you like.
• Switching to edit mode
  i allows you to insert text at the current cursor location, a allows you to append text just after the current cursor location.
• Switching back to command mode
  The escape key will take you back to command mode.
• Searching for a string
  Type / followed by the string of characters you want to search for. When you are finished press the enter key. The cursor will move to the first occurence of that string. Pressing n will move the cursor to the next occurence,
• Saving a file
  This is a command, and so you must type : first. The colon will appear on the bottom line. Now type w to write the file to disk.
• Quitting vi
  This is a command, and so you must type : first. The colon will appear on the bottom line. Now type q to quit vi. If you haven't written the file to disk since your last changes it will warn you instead of quitting. Use :wq to write-and-quit, or q! to quit without saving.

Many computer officers and other experienced Linux users like vi because it can do a lot with very few key presses, enabling an experienced vi user to rapidly edit files.