9.3 Standard streams - Stdio.stdin, stdout and stderr
Any UNIX program has three files open from the beginning. These are called
standard input, standard output and standard error stream. These streams
are available from Pike as well. They are called Stdio.stdin,
Stdio.stdout and Stdio.stderr respectively. Standard
input is a clone of Stdio.FILE, which means you can use the line
oriented functions. Stdio.stdout and Stdio.stderr are
simply clones of Stdio.File.
This example will read lines from standard input for as long as there
are more lines to read. Each line will then be written to stdout together
with the line number. We could use Stdio.stdout.write instead
of just write because they are the same function.