Linux - How to find and replace substring in text file.

sed -i 's/original/new/g' file.txt
Explanation:
  • sed = Stream EDitor
  • -i = in-place (i.e. save back to the original file)
The command string:
  • s = the substitute command
  • original = a regular expression describing the word to replace (or just the word itself)
  • new = the text to replace it with
  • g = global (i.e. replace all and not just the first occurrence)
  • file.txt = the file name