Remove DOS line endings from Text files (CR/LF)

dos2unix is a commandline utility that will do this.

Or in vim you can use:

:%s/\r/\r/g  or
:%s/^M//g  use Ctrl-v Ctrl-m to input the ^M
:set fileformat=unix

sed 's/^M$//' windows.txt > unix.txt
sed 's/\r$//' windows.txt > unix.txt
tr -d '\r' < windows.txt > unix.txt