How to insert text at beginning of a multi-line selection in vi/Vim

Solution 1:

Press Esc to enter 'command mode'
Use Ctrl+V to enter visual block mode
Move Up/Downto select the columns of text in the lines you want to comment.
Then hit Shift+i and type the text you want to insert.
Then hit Esc, wait 1 second and the inserted text will appear on every line.

For further information and reading, check out "Inserting text in multiple lines" in the Vim Tips Wiki.

Solution 2:

This replaces the beginning of each line with "//":

:%s!^!//!

This replaces the beginning of each selected line (use visual mode to select) with "//":

:'<,'>s!^!//!

Note that gv (in normal mode) restores the last visual selection, this comes in handy from time to time.

Solution 3:

The general pattern for search and replace is:

:s/search/replace/

Replaces the first occurrence of 'search' with 'replace' for current line

:s/search/replace/g

Replaces all occurrences of 'search' with 'replace' for current line, 'g' is short for 'global'

This command will replace each occurrence of 'search' with 'replace' for the current line only. The % is used to search over the whole file. To confirm each replacement interactively append a 'c' for confirm:

:%s/search/replace/c

Interactive confirm replacing 'search' with 'replace' for the entire file

Instead of the % character you can use a line number range (note that the '^' character is a special search character for the start of line):

:14,20s/^/#/

Inserts a '#' character at the start of lines 14-20

If you want to use another comment character (like //) then change your command delimiter:

:14,20s!^!//!

Inserts a '//' character sequence at the start of lines 14-20

Or you can always just escape the // characters like:

:14,20s/^/\/\//

Inserts a '//' character sequence at the start of lines 14-20

If you are not seeing line numbers in your editor, simply type the following

:set nu

Solution 4:

Another way that might be easier for newcomers:

 some█
 code
 here

Place the cursor on the first line, e.g. by

gg

and type the following to get into insert mode and add your text:

I / / Space

 // █some
 code
 here

Press Esc to get back to command mode and use the digraph:

j . j .

 // some
 // code
 //█here

j is a motion command to go down one line and . repeats the last editing command you made.

Solution 5:

And yet another way:

Move to the beginning of a line
enter Visual Block mode (CTRL-v)
select the lines you want (moving up/down with j/k, or jumping to a line with [line]G)
press I (that's capital i)
type the comment character(s)
press ESC