Macro warning

macro_rules! warning {
    ($($arg:tt)+) => { ... };
}

Macro to use warning() with a format string.

Example

struct FileSize;

impl Builtin for FileSize {
    fn call(&mut self, args: &mut Args) -> Result<()> {
        let stdout_handle = io::stdout();
        let mut output = BufWriter::new(stdout_handle.lock());

        let mut result = Ok(());

        for path in args.path_arguments() {
            match fs::metadata(&path) {
                Ok(m) => {
                    writeln!(&mut output, "{}\t{}", m.len(), path.display())?;
                }

                Err(e) => {
                    warning!("{}: {}", path.display(), e);
                    result = Err(Error::ExitCode(1));
                }
            }
        }

        result
    }
}