swlog

gistfile1.swift

public struct StderrOutputStream: OutputStreamType {
    
    // Support for file redirection back to console
    private static var fpos : fpos_t = 0
    private static var fd = dup(fileno(stderr))
    private static var isRedirected_ = false
    public static var isRedirected : Bool {return isRedirected_}
    
    // When false, the output file is rewritten and not appended
    private static var appendToFile = true
    
    // When true, output is echoed to stdout
    public static var echo = false
    
    // When non-nil, output is redirected to the specified file path
    public static func redirectOutputToPath(path: String?) {
        if let path = path {
            if !isRedirected {
                // Set up if this is new redirection
                fflush(stderr)
                var pos = UnsafeMutablePointer<fpos_t>.alloc(1)
                fgetpos(stderr, pos)
                fpos = pos.memory
                free(pos)
                fd = dup(fileno(stderr))
            }
            if appendToFile {
                freopen(path, "a", stderr)
            } else {
                freopen(path, "w", stderr)
            }
            isRedirected_ = true
        } else {
            if !isRedirected {
                // do not respond if not redirected
                return
            }
            fflush(stderr)
            dup2(fd, fileno(stderr))
            close(fd)
            clearerr(stderr)
            fsetpos(stderr, &fpos)
            isRedirected_ = false
        }
    }

    public static let stream = StderrOutputStream()
    public func write(string: String) {
        fputs(string, stderr)
        if StderrOutputStream.echo && StderrOutputStream.isRedirected {fputs(string, stdout)}
    }
}
public var errStream = StderrOutputStream.stream

func swlog(format : String, args : CVarArgType...) {
    println(String(format: format, arguments: args), &errStream)
}

What's with the underscore suffix in your private member - private static var isRedirected_ = false
Is this just a preference vs a prefixed underscore or is this preferred in Swift?