Create an executable file that copies stdin to stdout, or else a script that does so through the invocation of an interpreter at the command line.

import "io" for Stdin, Stdout
 
Stdin.isRaw = true // prevents echoing to the terminal
while (true) {
    var byte = Stdin.readByte()         // read a byte from stdin
    if (byte == 13) break               // break when enter key pressed
    System.write(String.fromByte(byte)) // write the byte (in string form) to stdout
    Stdout.flush()                      // flush output
}
System.print()
Stdin.isRaw = false