How do i use regular expressions with vi?

maltiger

A lot of this applies to vim also, most recent linux OS's will call vim.

Man page for vim: https://www.lightnetics.com/post/3435
Link to regular expressions: https://www.lightnetics.com/post/3348
Vim documentation on substitution: http://vimdoc.sourceforge.net/htmldoc/usr_10.html#10.2
Vim documentation on patterns: http://vimdoc.sourceforge.net/htmldoc/usr_27.html

The format of the regular expression when you presss colon in vi.

:

The format of the command is:

:[range]s[ubstitute]/pattern/string/[options]

Explaining each section.

The range are the line you want to target for changes.

The Range

. The dot means current line.

$ The dollar means last line.

* The visual area.

% The entire file.

'c The position of the mark c.

/{pattern}[/] The next line which matches the pattern.

?{pattern}[?] The previous line which matches the pattern.

& The next line where the previous substitution matches.

? The previous line where the previous substitution matches.

/ The next line where the previously used search matches.

The above can be used with with + and - (plus/minus) followed by an optional number, the default number is 1, if not provided. These symbols mean add or subtract to the preceding line match.

The s[ubstitute]

Means you are using the substutute option for text manipulation.

/pattern/

Means the what you are searching for in the file.

/string/

Means what you want the pattern to change to.

/options

Specify additional options.

Examples.

Sample file:

&lt!DOCTYPE html&gt
&lthtml&gt
&ltbody&gt

  &lth1>My First Heading&lt/h1&gt
  &lth1>My Second Heading&lt/h1&gt
  &ltp>My first paragraph.&lt/p&gt

&lt/body&gt
&lt/html&gt

g - Replace all occurrences in the line (without g - only first).

Change h1 to h2 only on line 5, ever occurrence on that line.

`:5s/h1/h2/g`

Same as above but confirming every change. Useful for testing.

`:5s/h1/h2/cg`

replace with h1 (y/n/a/q/l/^E/^Y)?
At this point, you must enter one of the following answers:

y		Yes; make this change.
n		No; skip this match.
a		All; make this change and all remaining ones without further confirmation.
q		Quit; don't make any more changes.
l		Last; make this change and then quit.
CTRL-E		Scroll the text one line up.
CTRL-Y		Scroll the text one line down.

Change all h1 tags to h2 tags in the entire file.