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18.4. vi @-Functions

The vi map command (Section 18.2) lets you define keymaps: short names for a series of one or more commands. You can enter :map to define a keymap while you're editing a file with vi. But if you make a mistake, you usually have to re-enter the whole :map command to correct the problem.

@-functions (pronounced "at-functions") give you another way to define complex commands. You can define 26 @-functions named @a through @z. They're stored in named buffers (Section 17.4). So if you're also using named buffers for copying and pasting text, you'll need to share them with your @-functions.

18.4.1. Defining and Using Simple @-Functions

To define an @-function:

  1. Enter the command(s) you want to execute onto one or more lines of the file you're editing.

  2. Yank or delete the line(s) into a named buffer with a command like "ay$ or "bD.

  3. To use the function, type a command like @a or @b. You can repeat the function by typing @@ or a dot (.). Use u or U to undo the effects of the @-function.

Here's an example. You're editing a long HTML file with lines like these:

<STRONG>Some heading here</STRONG>
<STRONG>Another heading here</STRONG>

When you see one of those lines, you need to change the STRONG s to either H3 or H4. A global substitution with :%s won't do the job because some lines need H3 and others need H4; you have to decide line-by-line as you work through the file. So you define the function @a to change a line to H3, and @b to change to H4.

To design an @-function, start by thinking how you'd make the changes by hand. You'd probably move to the start of the line with 0, move to the right one character with l, type cw to change the word STRONG, and type in H3 (or H4). Then you'd press ESC to return to command mode. After going to the end of the line with $, you'd move to the character after the slash with T/, then change the second STRONG the way you fixed the first one.

To define the function, open a new empty line of your file (first go into text-input mode). Then type the keystrokes that will make the H3 changes; type CTRL-v before each ESC or RETURN (Section 18.6). When you're done, press ESC again to go to command mode. Because the commands for the H4 change are similar, the easiest way to make them is by copying and pasting the line for H3 (by typing yy and p) and then editing the copy. The pair of command lines should look like this (where ^[ stands for the CTRL-v ESC keys):


Move to the start of the first line, and delete it into the a buffer by typing "aD. Go to the next line, and type "bD. (This will leave two empty lines; delete them with dd if you'd like.) Now, when you type @a, it will execute the commands to change a line to H3; typing @b on a line will change it to have H4. Move through your file (maybe with a search: /STRONG ... n ...), typing @a or @b as you go. Or use @@ to make the same change you made on a previous line.

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