2. Moving around.

2.1. w, e and b keystrokes

One can use the w , e and b keys to move around a file. VIM is capable of recognizing the different tokens within a C expression.

Consider the following C code

Figure 1. A C snippet

 
		  ...
		  if(( NULL == x ) && y > z )
		  ...
	       

Assume that the cursor is positioned at the beginning of the if statement. By pressing w once the cursor jumps to the first ( . By typing w again the cursor moves to NULL . Next time the cursor will move to the == token. Further keystrokes will take you as follows. x. .. ) ... && ... y ... > ... z ... and finally ) ...

e is similar to w only that it takes you to the end of the current word and not to the beginning of the next word.

b does the exact opposite of w . It moves the cursor in the opposite direction. So you can moving backwards using the b keystroke.

2.2. {, }, [[ and ]] keystrokes

The { and } keys are used to move from paragraph to paragraph. When editing C files these keys have a slightly different meaning. Here a paragraph is taken as a bunch of lines separated by an empty line.

For Example

Figure 2. Another C snippet

The above snippet shows two paragraphs. One can easily move from the beginning of one to the other, by using the { and } keys. { will take the cursor to the paragraph above and } will take the cursor to the paragraph below.

Many people have the coding style where a logical set of statements are grouped together and separated by one or more blank lines.

For Example

Figure 3. Another C snippet

The { and } keys are very useful in such situations. One can very easily move from one "paragraph" to another.

Another set of keys which are useful are the [[ and ]] keys. These keys allow you to jump to the previous { or next { in the first column.

For Example

Figure 4. The next snippet of C code

Lets say you were editing foo() and now you want to edit bar(). Just type ]] and the cursor will take you to the opening { of the bar() function. The reverse is slightly different. If you were in the middle of bar() and you type [[ the cursor will move to the first { above i.e. the beginning of bar() itself. One has to type [[ again to move to the beginning of foo(). The number of keystrokes can be minimized by typing 2[[ to take the cursor to the beginning of the previous function.

Another set of similar keystrokes are the ][ and [] keystrokes. ][ takes the cursor to next } in the first column. If you were editing foo() and wanted to go to the end of foo() then ][ will take you there. Similarly if you were editing bar() and wanted to go to the end of foo() then [] would take the cursor there.

The way to remember the keystrokes is by breaking them up. The first keystroke will indicated whether to move up or down. [ will move up and ] will move down. The next keystroke indicates the type of brace to match. If it same same as the previous keystroke then the cursor will move to {. If the keystroke is different then the cursor will move to }.

One caveat of the ]] , ][ , [[ and [] keystrokes is that they match the braces which are in the first column . If one wants to match all braces upwards and downwards regardless of whether its in the first column or not is not possible. The VIM documentation has a workaround. One has to map the keystrokes to find the braces. Without spending too much time on mapping, the suggested mappings are

:map [[ ?{<CTRL-VCTRL-M>w99[{

:map ][ /}<CTRL-VCTRL-M>b99]}

:map ]] j0[[%/{<CTRL-VCTRL-M>

:map [] k$][%?}<CTRL-VCTRL-M>

2.3. % keystroke

The % is used to match the item under the cursor. The item under the cursor can be a parenthesis, a curly bracket or a square bracket. By pressing the % key the cursor will jump to the corresponding match.

Amongst other things, the % keystroke can be used to match #if, #ifdef, #else #elif and #endif also.

This keystroke is very useful in validating code that one has written. For Example

Figure 5. The next snippet of C code

Checking the above code will involve checking the correctness of the parenthesis. The % can be used to jump from one ( to its corresponding ) and vice versa. Thus, one can find which opening parenthesis corresponds to which closing parenthesis and use the information to validate the code.

Similarly the % can also be used to jump from a { to its corresponding }.