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

Let N be a shell variable representing the count of characters after which you want a newline. If you want to continue the count accross lines:

perl -0xff -pe 's/(.{'$N'})/$1\n/sg' input

If you want to restart the count for each line, omit the -0xff argument.