ReadStandardInput.swift

func input(_ block: (UInt8) -> (Bool)) {
    func initStruct<S>() -> S {
        let struct_pointer = UnsafeMutablePointer<S>.allocate(capacity: 1)
        let struct_memory = struct_pointer.pointee
        struct_pointer.deallocate()
        return struct_memory
    }

    func enableRawMode(fileHandle: FileHandle) -> termios {
        var raw: termios = initStruct()
        tcgetattr(fileHandle.fileDescriptor, &raw)
        let original = raw
        raw.c_lflag &= ~(UInt(ECHO | ICANON))
        tcsetattr(fileHandle.fileDescriptor, TCSAFLUSH, &raw);
        return original
    }

    func restoreRawMode(fileHandle: FileHandle, originalTerm: termios) {
        var term = originalTerm
        tcsetattr(fileHandle.fileDescriptor, TCSAFLUSH, &term);
    }

    let stdIn = FileHandle.standardInput
    let originalTerm = enableRawMode(fileHandle: stdIn)

    var char: UInt8 = 0
    while read(stdIn.fileDescriptor, &char, 1) == 1 {
        let keepListening = block(char)
        if !keepListening {
            break
        }
    }
    restoreRawMode(fileHandle: stdIn, originalTerm: originalTerm)
}

// Usage
input { (inputValue) -> (Bool) in
    // return true to keep listening
    return true
}