Copy stdin to stdout

Copy stdin to stdout is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

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.

ALGOL 68

Works with: ALGOL 68G version Any - tested with release 2.8.3.win32

<lang algol68>BEGIN

   BOOL at eof := FALSE;
   # set the EOF handler for stand in to a procedure that sets "at eof" to true #
   # and returns true so processing can continue                                #                               
   on logical file end( stand in, ( REF FILE f )BOOL: at eof := TRUE );
   # copy stand in to stand out                                                 #
   WHILE STRING line; read( ( line, newline ) ); NOT at eof DO write( ( line, newline ) ) OD

END</lang>

AWK

Using the awk interpreter, the following command uses the pattern // (which matches anything) with the default action (which is to print the current line) and so copy lines from stdin to stdut. <lang AWK>awk "//"</lang>

C

<lang C>

1. include <stdio.h>

int main(){

 char c;
 while ( (c=getchar()) != EOF ){
   putchar(c);
 }
 return 0;

} </lang>

Go

<lang go>package main

import (

   "bufio"
   "io"
   "os"

)

func main() {

   r := bufio.NewReader(os.Stdin)
   w := bufio.NewWriter(os.Stdout)
   for {
       b, err := r.ReadByte()       
       if err == io.EOF {
           return
       }
       w.WriteByte(b)
       w.Flush()
   }   

}</lang>

Mercury

<lang Mercury>

- module stdin_to_stdout.

- interface.

- import_module io.

- pred main(io::di, io::uo) is det.

%-----------------------------------------------------------------------------% %-----------------------------------------------------------------------------%

- implementation.

- import_module char.

- import_module list.

- import_module string.

%-----------------------------------------------------------------------------%

main(!IO) :-

   io.read_line_as_string(Result, !IO),
   (
       Result = ok(Line),
       io.write_string(Line, !IO),
       main(!IO)
   ;
       Result = eof
   ;
       Result = error(Error),
       io.error_message(Error, Message),
       io.input_stream_name(StreamName, !IO),
       io.progname("stdin_to_stdout", ProgName, !IO),
       io.write_strings([
           ProgName, ": ",
           "error reading from `", StreamName, "': \n\t",
           Message, "\n"
       ], !IO)
   ).

%-----------------------------------------------------------------------------% </lang>

Perl

<lang perl> perl -pe </lang>

Perl 6

When invoked at a command line: Slightly less magical than Perl / sed. The p flag means automatically print each line of output to STDOUT. The e flag means execute what follows inside quotes. ".lines" reads lines from the assigned pipe (file handle), STDIN by default.

<lang perl6>perl6 -pe'.lines'</lang>

When invoked from a file: Lines are auto-chomped, so need to re-add newlines (hence .say rather than .print) <lang perl6>.say for lines</lang>

Prolog

<lang Prolog> %File: stdin_to_stdout.pl

- initialization(main).

main :- repeat, get_char(X), put_char(X), X == end_of_file, fail. </lang>

Invocation at the command line (with Swi-prolog): <lang sh> swipl stdin_to_stdout.pl </lang>

sed

<lang sh> sed -e </lang>

zkl

<lang zkl>zkl --eval "File.stdout.write(File.stdin.read())"</lang>