title: Batch replace text inside text file (Linux/OSX Commandline)
body: <p>I have hundreds of files where I need to change a portion of its text.</p>
  
  <p>For example, I want to replace every instance of "http://" with "rtmp://" .</p>
  
  <p>The files have the .txt extention and are spread across several folders and subfolder.</p>
  
  <p>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".</p>