Problem Statement

A common practice in computing is to send error messages to a different output stream than normal text console messages. The normal messages print to what is called "standard output" or "standard out". The error messages print to "standard error". This separation can be used to redirect error messages to a different place than normal messages.

Show how to print a message to standard error by printing     Goodbye, World!     on that stream.

Let's start with the solution:

prerr_endline "Goodbye, World!";    (* this is how you print a string with newline to stderr *)
Printf.eprintf "Goodbye, World!\n"; (* this is how you would use printf with stderr *)


output_string stderr "Goodbye, World!\n";
Printf.fprintf stderr "Goodbye, World!\n";


let msg = "Goodbye, World!\n" in
ignore(Unix.write Unix.stderr msg 0 (String.length msg)) ;;