Copy stdin to stdout in Java

inout.java

import java.io.IOException;

/**
 * Class that copies stdin to stdout, as compained about as not being cleanly
 * writable in Java on Hacker News.
 * In real code, you would just write IOUtils.copy(System.in, System.out),
 * which does basically the same thing.
 * This does not catch any exceptions as a) this is just an "exercise" and
 * b) all we could do with them is pretty-print them. So let the runtime 
 * print them for you.
 *
 * Usage: javac inout.java && echo -e "foo\nbar" | java InOut
 */
class InOut {
    public static void main(String[] args) throws IOException {
        byte[] buffer = new byte[8192];
        while(true) {
            int bytesRead = System.in.read(buffer);
            if (bytesRead == -1) {
                return;
            }
            System.out.write(buffer, 0, bytesRead);
        }
    }
}

In Racket:

(display (read (current-input-port)))

#!/usr/bin/env ruby
IO.copy_stream(STDIN, STDOUT)

C#

using System;

public class Program
{
    public static void Main()
    {
        while(true)
        {
            int input = Console.In.Read();
            if(input == -1) break;
            Console.Out.Write((char)input);
        }
    }
}

@ssijak I think you misunderstood what that Java program does. It copies the input verbatim to the output.

$ printf 'hello\nworld\n' | python3 -c 'print(input())'
hello
$

It also mangles binary data since it uses print() which will add a newline to the end of its arguments by default (try end='' to never write a final newline).

$ printf 'binarydata' | python3 -c 'print(input())' | hexdump -C
00000000  62 69 6e 61 72 79 64 61  74 61 0a                 |binarydata.|
0000000b

instead of...

$ printf 'binarydata' | hexdump -C
00000000  62 69 6e 61 72 79 64 61  74 61                    |binarydata|
0000000a
$

Observe there is no newline in the last example.

@17twenty I don't think your program respects binary data either because the print statement needs a final comma to suppress the final newline.
@rShetty Your example appears to only copy the first line in Ruby. Does puts add a final newline as well?

Anything that "gets a line" uses a newline as a sentinel value and is not a solution. The sentinel of an input stream is an EOF marker (in python the sentinel is an empty string returned from the .read() method). I think Programming Pearls has a section about the importance of an unique sentinel value.

Python

Using partial as suggested in Transforming Code into Beautiful Idiomatic Python (the example slide):

from functools import partial
from sys import stdout, stdin

for block in iter(partial(stdin.read, 32), ''):
    stdout.write(block)

Note that partial is optional — lambda: stdin.read(32) also works.

/In C/

include <stdio.h>

int main(int argc, char **argv)
{
int c;
while((c = getchar()) != EOF)
putchar(c);
return 0;
}

in bash:
echo

In French:

Copiez entrée à la sortie

In Go:

io.Copy(os.Stdout, os.Stdin)

Libraryless:

b := make([]byte, 1024)
for n, err := os.Stdin.Read(b); err == nil; n, err = os.Stdin.Read(b) {
    os.Stdout.Write(b[:n])
}

In Turkish:

Girdiyi çıktıya aktar.

uhh I dont understand why this isnt a valid solution 

import java.util.Scanner; 

public class Main
{

  public static void main (String[]args) 
  {
    while(true)
    {
        Scanner sc = new Scanner(System.in);
        System.out.println(sc.nextLine());
    }
  }
}