Improved println!

improved_println.rs

/// Improved println! macro that allows specifying stdout or stderr
///
/// # Examples
///
/// Printing to stdout works like normal
/// ```rust
/// zprintln!("Hello, zprintln!");
/// ```
///
/// Printing to stderr works by passing a special argument
/// ```rust
/// zprintln!(stderr, "Hello, stderr!");
/// ```
macro_rules! zprintln {
    (stdout, $($arg:tt)*) => {
        println!($($arg)*);
    };
    (stderr, $($arg:tt)*) => {{
        use std::io::Write;
        writeln!(::std::io::stderr(), $($arg)*).unwrap();
    }};
    ($($arg:tt)*) => {
        println!($($arg)*);
    };
}

fn main() {
    zprintln!("normal shows up on stdout");
    zprintln!("normal shows up on stdout with arg: {}", 1);
    zprintln!(stdout, "with stdout goes to stdout: {}", 1);
    zprintln!(stderr, "with stderr goes to stderr: {}", 2);
}

Output:

jwilm@Joes-MBP ➜  ~/sandbox/zprintln/target/debug  ./zprintln > /dev/null
with stderr goes to stderr: 2
jwilm@Joes-MBP ➜  ~/sandbox/zprintln/target/debug  ./zprintln 2> /dev/null
normal shows up on stdout
normal shows up on stdout with arg: 1
with stdout goes to stdout: 1
jwilm@Joes-MBP ➜  ~/sandbox/zprintln/target/debug