How to check if a file contains a specific string using Bash

 In case if you want to check whether file does not contain a specific string, you can do it as follows.

if ! grep -q SomeString "$File"; then

  Some Actions # SomeString was not found

fi

from: https://stackoverflow.com/questions/11287861/how-to-check-if-a-file-contains-a-specific-string-using-bash

sed command with -i option failing on Mac, but works on Linux

 I believe on OS X when you use -i an extension for the backup files is required. Try:

sed -i .bak 's/hello/gbye/g' *

Using GNU sed the extension is optional.

from: https://stackoverflow.com/questions/4247068/sed-command-with-i-option-failing-on-mac-but-works-on-linux