stderr-stream-2_2.swift

import Darwin

extension Process {

    // See also: https://github.com/apple/swift/blob/9cdbec13eee72feccfc5f8b987882a8c52e8107b/stdlib/private/SwiftPrivate/IO.swift#L84
    public struct Stream: OutputStreamType {
        private let fd: UnsafeMutablePointer<FILE>
        private init(fd: UnsafeMutablePointer<FILE>) {
            self.fd = fd
        }

        public func write(string: String) {
            flockfile(fd)
            for c in string.utf8 {
                putc_unlocked(numericCast(c), fd)
            }
            funlockfile(fd)
        }
    }

    @_transparent
    public static var stdout: Stream {
        get {
            return Stream(fd: Darwin.stdout)
        }
        set { }
    }

    @_transparent
    public static var stderr: Stream {
        get {
            return Stream(fd: Darwin.stderr)
        }
        set { }
    }

}

print("I am an error!", toStream: &Process.stderr)