Question

In section 1.6 of ‘The C Programming Language’ (K&R) there is an example program and the authors state:

The output of this program ON ITSELF is
    digits = 9 3 0 0 0 0 0 0 0 1, white space = 123, other = 345

Then there are many similar programs etc. including exercises. I understand everything about the logic of the code and can do the exercises, but how do I actually test my program on a file like the authors or many others on the web?

Edit: The question should be: How can I redirect the input of a file to the program?

Answer 1

The program in chapter 1.6 reads input from stdin. To make it read from a file, you can (on most operating systems) redirect stdin to be a file by running your program like this:

myprogram < somefile

Or you can pipe the content of a file to it like so:

cat somefile | myprogram

On windows, you’d use the type program instead of cat,

type somefile | myprogram