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

Question

I\'ve successfully used the following sed command to search/replace text in Linux:

sed -i \'s/old_link/new_link/g\' *

However,

Answer 1

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.