Let's just pretend for one second that this is actually 100% a useful pacakge and so I will choose to write this documentation as though it will actually be worth while. But really, it's not at all that impressive, nor is this code truly mine. But I did learn a lot, and I will be building my own node package shortly.... I digress.
npm install replacethis
replacethis [file] [searchWord] [replaceWith]
Example:
replacethis test.txt dog cat
The contents will be output into a new file out.txt.
Credits owed to praveenvijayan on his great post