Convert a text file's encoding
From ArchWiki
Note: This page is just a little reminder.
Characters' encoding problems are well-known and of course there is a simple solution on linux to change a file's encoding.
This solution is named: iconv which is provided by the glibc package which is in core.
The following command will convert the foo file from ISO-8859-15 to UTF-8 saving it to foo.utf:
$ iconv -f ISO-8859-15 -t UTF-8 foo > foo.utf
The manual page of this program is pretty clear so refer to it for more advanced usage.