Best way to read stdin that may include newline?

Best way to read stdin that may include newline?

I have to write a program in C that handles the newline as part of a
string. I need a way of handling the newline char such that if it is
encountered it doesn't necessarily terminate the input. So far I've been
using fgets() but that stops as soon as it reaches a '\n' char. Is there a
good function for processing the input from the console that doesn't
necessarily end at the newline character?
To clarify: I need a method that doesn't terminate at the newline char
because in this particular exercise when the newline char is encountered
it's replaced with a space char.