edit a string in multiple files: sed -ic
Sed is a great tool used to edit one line if needed for multiple files without open it.
Usually to do this, you just need to:
1. Looking for the right regular expression:
grep -re “user” /my/dir
2. Inject the update string
sed -ic ‘s/user/newuser/g’ <filename>
WARNING : the option “-c” is needed to preservate the owner of the file, if not set the file change permission with the actual owner.