How to insert a new line character after a fixed number of characters in a file

Question

I am looking for a bash or sed script (preferably a one-liner) with which I can insert a new line character after a fixed number of characters in huge text file.

Answer 1

This might work for you:

echo aaaaaaaaaaaaaaaaaaaax | sed 's/./&\n/20'
aaaaaaaaaaaaaaaaaaaa
x