why-vi.rocks/index.md

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<img class="mt4" src="vi-sw.png">

_[vi](https://en.wikipedia.org/wiki/Vi) is the **de facto** standard
text editor in any Unix-like operating system._

Here is a collection of [vi(1)](https://man.openbsd.org/vi.1)/[ex(1)](https://man.openbsd.org/ex.1) commands and command sequences.<br>
Tested with [nvi](https://en.wikipedia.org/wiki/Nvi) 1.79 and 2.1.3 (unicode).


## Yank/delete lines

(1) mark the first line: `mk`<br>
(2) move to last line<br>
(3a) yank: `y'k`<br>
(3b) delete: `d'k`<br>
(4) move to destination line<br>
(5) put with `P` or `p`<br>


## Apply regex to lines

(1) mark the first line: `mk`<br>
(2) mark the last line: `ml`<br>

<pre>
:'k,'ls/<em>regex</em>/<em>power</em>/g
</pre>


## Increment / Decrement number in command mode

(1) move cursor to number<br>
(2a) increment by one: #+<br>
(2b) increment by N (5): 5#+<br>
(3a) decrement by one: #-<br>
(3b) decrement by N (9): 9#-


## Add &#35; to a block

<pre>
:'k,'ls/^/#/
</pre>


## Remove trailing whitespace from a block

	:'k,'ls/\ *$//


## Remove the first N-characters from every line

N = 5

<pre>
:%s/^.\{0,<em>5</em>\}//
</pre>


## Delete all lines N-character long

N = 10

<pre>
:g/^.\{<em>10</em>\}$/d
</pre>


## Delete all lines _except_ N-character long

N = 10

<pre>
:g!/^.\{<em>10</em>\}$/d
</pre>


## Search/replace paths using &#35; as delimiter

<pre>
:%s#<em>/usr/local/log</em>#<em>/var/log</em>#g
</pre>


## Write the file as root

	:w !doas tee %


## Diff the file on disk with the buffer

	:w !diff -u % -


## Make a backup of the file on disk

	:!cp % %.bak


## Sort all lines

	:%!sort


## Sort a block

`}` won't be shown

<pre>
!<u>}</u>sort
</pre>


## Sort from the current line to EOF

`G` won't be shown

<pre>
!<u>G</u>sort
</pre>


## Delete duplicated lines in the file

	:%!uniq

## Delete duplicated lines in the block

`}` won't be shown

<pre>
!<u>}</u>uniq
</pre>

## Delete duplicated lines till EOF

`G` won't be shown

<pre>
!<u>G</u>uniq
</pre>


## Underline all lines starting with `pattern`

<pre>
:g/^<em>pattern</em> /t.|s/./=/g
</pre>


## Search for `pattern`, print the containing function (start with `def`) and line number

<pre>
:g/<em>pattern</em>/?^ *<em>def</em> ?#
</pre>


## Add &#35; to paragraph containing `pattern`

<pre>
:g/<em>pattern</em>/?^$?+,//-s/^/#
</pre>


## Sort content of a multiline CSS block

	:g/{$/+,/^}/-!sort


## Sort content of a multiline CSS block (media queries)

	:g/^[^@].*{$/+,/}/-!sort


## Format content of `<p>` tag to fixed width

width = 40

<pre>
:g/&lt;p&gt;/+,/&lt;\/p&gt;/-!fmt -<em>40</em>
</pre>


## Reverse all lines, move `m` all lines to 0

	:g/1*/m0


## Swap `Lastname, Firstname` to `Firstname, Lastname`

	:%s/\(.*\), \(.*\)/\2 \1/


## Convert to lowercase

	:%s/.*/\L&/


## Join all lines

	:%j

## Copy `t` or move `m` lines containing `pattern`

<pre>
:g/<em>pattern</em>/t$
:g/<em>pattern</em>/m$
</pre>

## Select a column of a table
Select 3rd column separated by colon (`:`)

<pre>
:%!awk -F'<em>:</em>' '{print $<em>3</em>}'
</pre>

## Insert the sum of a list of numbers after an arbitrary number of lines

(1) mark the first line: `mk`
(2) mark the last line: `ml`

<pre>
:'k,'l!awk 'END{print "<em>total:</em>", i}{i+=$1; print}'
</pre>

or

<pre>
:'k,'l!awk 'END{print "<em>total:</em>", i} ++i || 1'
</pre>

## Email the block

<pre>
:?^$?+,//-w !mail -s "<em>subject</em>" <em>email@example.com</em>
</pre>

## Enable and use `ex` history

(1) Set `ESC` key to enable history or add to `~/.exrc`:

<pre>
:set cedit=<u>&lt;CTRL-V&gt;&lt;ESC&gt;</u>
</pre>

(2) Use it with:

<pre>
:<u>&lt;ESC&gt;</u>
</pre>