Batch replace text inside text file (Linux/OSX Commandline)

I have hundreds of files where I need to change a portion of its text.

For example, I want to replace every instance of "http://" with "rtmp://" .

The files have the .txt extention and are spread across several folders and subfolder.

I basically am looking for a way/script that goes trough every single folder/subfolder and every single file and if it finds inside that file the occurrence of "http" to replace it with "rtmp".

You can do this with a combination of find and sed:

find . -type f -name \*.txt -exec sed -i.bak 's|http://|rtmp://|g' {} +

This will create backups of each file. I suggest you check a few to make sure it did what you want, then you can delete them using

find . -name \*.bak -delete

Here's a zsh function I use to do this:

change () {
        from=$1 
        shift
        to=$1 
        shift
        for file in $*
        do
                perl -i.bak -p -e "s{$from}{$to}g;" $file
                echo "Changing $from to $to in $file"
        done
}

It makes use of the nice Perl mechanism to create a backup file and modify the nominated file. You can use the above to iterate through files thus: