How to convert the ^M linebreak to 'normal' linebreak in a file opened in vim?

Command

:%s/<Ctrl-V><Ctrl-M>/\r/g

Where <Ctrl-V><Ctrl-M> means type Ctrl+V then Ctrl+M.

Explanation

:%s

substitute, % = all lines

<Ctrl-V><Ctrl-M>

^M characters (the Ctrl-V is a Vim way of writing the Ctrl ^ character and Ctrl-M writes the M after the regular expression, resulting to ^M special character)

/\r/

with new line (\r)

g

And do it globally (not just the first occurrence on the line).

Within vim, look at the file format — DOS or Unix:

:set filetype=unix

:set fileformat=unix

The file will be written back without carriage return (CR, ^M) characters.

On Linux and Mac OS, the following works,

:%s/^V^M/^V^M/g

where ^V^M means type Ctrl+V, then Ctrl+M.

_{Note: on Windows you probably want to use ^Q instead of ^V, since by default ^V is mapped to paste text.}