91
\$\begingroup\$

One of the most common standard tasks (especially when showcasing esoteric programming languages) is to implement a "cat program": read all of STDIN and print it to STDOUT. While this is named after the Unix shell utility cat it is of course much less powerful than the real thing, which is normally used to print (and concatenate) several files read from disc.

Task

You should write a full program which reads the contents of the standard input stream and writes them verbatim to the standard output stream. If and only if your language does not support standard input and/or output streams (as understood in most languages), you may instead take these terms to mean their closest equivalent in your language (e.g. JavaScript's prompt and alert). These are the only admissible forms of I/O, as any other interface would largely change the nature of the task and make answers much less comparable.

The output should contain exactly the input and nothing else. The only exception to this rule is constant output of your language's interpreter that cannot be suppressed, such as a greeting, ANSI color codes or indentation. This also applies to trailing newlines. If the input does not contain a trailing newline, the output shouldn't include one either! (The only exception being if your language absolutely always prints a trailing newline after execution.)

Output to the standard error stream is ignored, so long as the standard output stream contains the expected output. In particular, this means your program can terminate with an error upon hitting the end of the stream (EOF), provided that doesn't pollute the standard output stream. If you do this, I encourage you to add an error-free version to your answer as well (for reference).

As this is intended as a challenge within each language and not between languages, there are a few language specific rules:

  • If it is at all possible in your language to distinguish null bytes in the standard input stream from the EOF, your program must support null bytes like any other bytes (that is, they have to be written to the standard output stream as well).
  • If it is at all possible in your language to support an arbitrary infinite input stream (i.e. if you can start printing bytes to the output before you hit EOF in the input), your program has to work correctly in this case. As an example yes | tr -d \\n | ./my_cat should print an infinite stream of ys. It is up to you how often you print and flush the standard output stream, but it must be guaranteed to happen after a finite amount of time, regardless of the stream (this means, in particular, that you cannot wait for a specific character like a linefeed before printing).

Please add a note to your answer about the exact behaviour regarding null-bytes, infinite streams, and extraneous output.

Additional rules

  • This is not about finding the language with the shortest solution for this (there are some where the empty program does the trick) - this is about finding the shortest solution in every language. Therefore, no answer will be marked as accepted.

  • Submissions in most languages will be scored in bytes in an appropriate preexisting encoding, usually (but not necessarily) UTF-8.

    Some languages, like Folders, are a bit tricky to score. If in doubt, please ask on Meta.

  • Feel free to use a language (or language version) even if it's newer than this challenge. Languages specifically written to submit a 0-byte answer to this challenge are fair game but not particularly interesting.

    Note that there must be an interpreter so the submission can be tested. It is allowed (and even encouraged) to write this interpreter yourself for a previously unimplemented language.

    Also note that languages do have to fulfil our usual criteria for programming languages.

  • If your language of choice is a trivial variant of another (potentially more popular) language which already has an answer (think BASIC or SQL dialects, Unix shells or trivial Brainfuck derivatives like Headsecks or Unary), consider adding a note to the existing answer that the same or a very similar solution is also the shortest in the other language.

  • Unless they have been overruled earlier, all standard rules apply, including the http://meta.codegolf.stackexchange.com/q/1061.

As a side note, please don't downvote boring (but valid) answers in languages where there is not much to golf; these are still useful to this question as it tries to compile a catalogue as complete as possible. However, do primarily upvote answers in languages where the author actually had to put effort into golfing the code.

Catalogue

The Stack Snippet at the bottom of this post generates the catalogue from the answers a) as a list of shortest solution per language and b) as an overall leaderboard.

To make sure that your answer shows up, please start your answer with a headline, using the following Markdown template:

## Language Name, N bytes

where N is the size of your submission. If you improve your score, you can keep old scores in the headline, by striking them through. For instance:

## Ruby, <s>104</s> <s>101</s> 96 bytes

If there you want to include multiple numbers in your header (e.g. because your score is the sum of two files or you want to list interpreter flag penalties separately), make sure that the actual score is the last number in the header:

## Perl, 43 + 2 (-p flag) = 45 bytes

You can also make the language name a link which will then show up in the snippet:

## [><>](http://esolangs.org/wiki/Fish), 121 bytes

<style>body { text-align: left !important} #answer-list { padding: 10px; width: 290px; float: left; } #language-list { padding: 10px; width: 290px; float: left; } table thead { font-weight: bold; } table td { padding: 5px; }</style><script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <link rel="stylesheet" type="text/css" href="//cdn.sstatic.net/codegolf/all.css?v=83c949450c8b"> <div id="language-list"> <h2>Shortest Solution by Language</h2> <table class="language-list"> <thead> <tr><td>Language</td><td>User</td><td>Score</td></tr> </thead> <tbody id="languages"> </tbody> </table> </div> <div id="answer-list"> <h2>Leaderboard</h2> <table class="answer-list"> <thead> <tr><td></td><td>Author</td><td>Language</td><td>Size</td></tr> </thead> <tbody id="answers"> </tbody> </table> </div> <table style="display: none"> <tbody id="answer-template"> <tr><td>{{PLACE}}</td><td>{{NAME}}</td><td>{{LANGUAGE}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr> </tbody> </table> <table style="display: none"> <tbody id="language-template"> <tr><td>{{LANGUAGE}}</td><td>{{NAME}}</td><td>{{SIZE}}</td><td><a href="{{LINK}}">Link</a></td></tr> </tbody> </table><script>var QUESTION_ID = 62230; var ANSWER_FILTER = "!t)IWYnsLAZle2tQ3KqrVveCRJfxcRLe"; var COMMENT_FILTER = "!)Q2B_A2kjfAiU78X(md6BoYk"; var OVERRIDE_USER = 8478; var answers = [], answers_hash, answer_ids, answer_page = 1, more_answers = true, comment_page; function answersUrl(index) { return "//api.stackexchange.com/2.2/questions/" + QUESTION_ID + "/answers?page=" + index + "&pagesize=100&order=desc&sort=creation&site=codegolf&filter=" + ANSWER_FILTER; } function commentUrl(index, answers) { return "//api.stackexchange.com/2.2/answers/" + answers.join(';') + "/comments?page=" + index + "&pagesize=100&order=desc&sort=creation&site=codegolf&filter=" + COMMENT_FILTER; } function getAnswers() { jQuery.ajax({ url: answersUrl(answer_page++), method: "get", dataType: "jsonp", crossDomain: true, success: function (data) { answers.push.apply(answers, data.items); answers_hash = []; answer_ids = []; data.items.forEach(function(a) { a.comments = []; var id = +a.share_link.match(/\d+/); answer_ids.push(id); answers_hash[id] = a; }); if (!data.has_more) more_answers = false; comment_page = 1; getComments(); } }); } function getComments() { jQuery.ajax({ url: commentUrl(comment_page++, answer_ids), method: "get", dataType: "jsonp", crossDomain: true, success: function (data) { data.items.forEach(function(c) { if (c.owner.user_id === OVERRIDE_USER) answers_hash[c.post_id].comments.push(c); }); if (data.has_more) getComments(); else if (more_answers) getAnswers(); else process(); } }); } getAnswers(); var SCORE_REG = /<h\d>\s*([^\n,<]*(?:<(?:[^\n>]*>[^\n<]*<\/[^\n>]*>)[^\n,<]*)*),.*?(\d+)(?=[^\n\d<>]*(?:<(?:s>[^\n<>]*<\/s>|[^\n<>]+>)[^\n\d<>]*)*<\/h\d>)/; var OVERRIDE_REG = /^Override\s*header:\s*/i; function getAuthorName(a) { return a.owner.display_name; } function process() { var valid = []; answers.forEach(function(a) { var body = a.body; a.comments.forEach(function(c) { if(OVERRIDE_REG.test(c.body)) body = '<h1>' + c.body.replace(OVERRIDE_REG, '') + '</h1>'; }); var match = body.match(SCORE_REG); if (match) valid.push({ user: getAuthorName(a), size: +match[2], language: match[1], link: a.share_link, }); else console.log(body); }); valid.sort(function (a, b) { var aB = a.size, bB = b.size; return aB - bB }); var languages = {}; var place = 1; var lastSize = null; var lastPlace = 1; valid.forEach(function (a) { if (a.size != lastSize) lastPlace = place; lastSize = a.size; ++place; var answer = jQuery("#answer-template").html(); answer = answer.replace("{{PLACE}}", lastPlace + ".") .replace("{{NAME}}", a.user) .replace("{{LANGUAGE}}", a.language) .replace("{{SIZE}}", a.size) .replace("{{LINK}}", a.link); answer = jQuery(answer); jQuery("#answers").append(answer); var lang = a.language; lang = jQuery('<a>'+lang+'</a>').text(); languages[lang] = languages[lang] || {lang: a.language, lang_raw: lang.toLowerCase(42), user: a.user, size: a.size, link: a.link}; }); var langs = []; for (var lang in languages) if (languages.hasOwnProperty(lang)) langs.push(languages[lang]); langs.sort(function (a, b) { if (a.lang_raw > b.lang_raw) return 1; if (a.lang_raw < b.lang_raw) return -1; return 0; }); for (var i = 0; i < langs.length; ++i) { var language = jQuery("#language-template").html(); var lang = langs[i]; language = language.replace("{{LANGUAGE}}", lang.lang) .replace("{{NAME}}", lang.user) .replace("{{SIZE}}", lang.size) .replace("{{LINK}}", lang.link); language = jQuery(language); jQuery("#languages").append(language); } }</script>

\$\endgroup\$
14
  • 62
    \$\begingroup\$ Bash, 3 bytes: cat \$\endgroup\$ – TheDoctor Oct 31 '15 at 19:02
  • 3
    \$\begingroup\$ @TheDoctor I guess this would fall into the "don't use a builtin which does exactly what is needed" rule. \$\endgroup\$ – Paŭlo Ebermann Oct 31 '15 at 19:46
  • 8
    \$\begingroup\$ @PaŭloEbermann There is no such rule, and the corresponding standard loophole is no longer accepted. (In fact, there is already a sh answer using cat which also contains a shorter solution using dd.) \$\endgroup\$ – Martin Ender Oct 31 '15 at 20:25
  • 1
    \$\begingroup\$ If only it used standard methods of input and output: ///, 0 bytes. \$\endgroup\$ – sporklpony Mar 31 '17 at 19:33
  • 1
    \$\begingroup\$ @SparklePony Except, you'd have to escape slashes and backslashes. \$\endgroup\$ – Martin Ender Mar 31 '17 at 20:35

292 Answers 292

1 2
3
4 5
10
3
\$\begingroup\$

Brain-Flak, 0 + 3 = 3 bytes

Needs the -c flag.


Try it online!

This language cannot possibly handle infinite input streams.

This language absolutely always appends a trailing newline to the output.

In the original Ruby interpreter, the input is a command-line arg instead of a STDIN stream. The online interpreter seems to have been modified.

\$\endgroup\$
3
\$\begingroup\$

05AB1E, 4 2 bytes (not working)

Try it online!

Golfed from 4 to 2 bytes thanks to @daHugLenny!

Explanation

|       Takes input as array separated by breaks
 »      Join input array by newline
        Implicitly print
\$\endgroup\$
8
3
\$\begingroup\$

Retina, 3 1 byte



That's a single linefeed.

Try it online!

The empty Retina program would count the number of matches of the empty regex in the input, so it can't compete with rs and sed here. There are several ways to implement a cat program, the shortest being a Replace stage that doesn't actually replace anything.

Retina cannot handle infinite streams (as it waits for EOF before starting any processing).

\$\endgroup\$
0
3
\$\begingroup\$

Shakespeare Programming Language, 96 bytes

,.Ajax,.Page,.Act I:.Scene I:.[Exeunt][Enter Page and Ajax]Ajax:Open mind!Speak thy!Let usAct I!

Try it online!

Some nice and weird grammer. Terminates in an error.

Shakespeare Programming Language, 125 bytes

,.Ajax,.Page,.Act I:.Scene I:.[Exeunt][Enter Page and Ajax]Ajax:Open mind!Be you nicer a pig?If sospeak thy!If solet usAct I!

Try it online!

Non-erroring version. I especially liked constructing the sentence If solet usact I!

\$\endgroup\$
3
\$\begingroup\$

Grocery List, 14 bytes

*but it doesn't look like a grocery list

h

i
l
p
i
e
t

Explanation:

Title

i nput
l oop
p op and print
i nput
e nd loop if nonzero
t erminate
\$\endgroup\$
3
\$\begingroup\$

Pyramid Scheme, 199 116 bytes

Saved 83 bytes thanks to Khuldraeseth na'Barya! Clever idea to use the "nameless" variable, an empty triangle.

   ^
  /d\
 / o \
^-----^
-    ^-^
    ^-/ \
   ^-/out\
  / \-----^
 /set\    -
^-----^
-    /l\
    /ine\
    -----

Try it online!


Old version (functionally equivalent)

      ^
     / \
    /do \
   ^-----^
  /A\   / \
  ---  /   \
      /     \
     /       \
    ^---------^
   / \       / \
  /set\     /out\
 ^-----^   ^-----
/A\   /l\ /A\
---  /ine\---
     -----

Try it online!

Explanation

This might look like this in a scheme/lisp-like language:

(do (pair (set A read-line) (print A)) A)

Or, in a C-like language:

do {
    A = gets();
    puts(A);
} while(A);
\$\endgroup\$
5
  • \$\begingroup\$ 125 bytes \$\endgroup\$ – Khuldraeseth na'Barya Jul 25 '19 at 18:24
  • \$\begingroup\$ 116 \$\endgroup\$ – Khuldraeseth na'Barya Jul 25 '19 at 18:26
  • \$\begingroup\$ @Khuldraesethna'Barya Fascinating structure... Thanks! \$\endgroup\$ – Conor O'Brien Jul 26 '19 at 0:35
  • \$\begingroup\$ Can you add some documentation for this language? I would like to try it out \$\endgroup\$ – Jo King Jul 26 '19 at 6:23
  • 1
    \$\begingroup\$ @JoKing Sure thing! I'm going off to bed rn, I'll add it to my todo list and I'll ping you once I'm done. \$\endgroup\$ – Conor O'Brien Jul 26 '19 at 6:24
3
\$\begingroup\$

Keg, 0 8 bytes

{?(,)\
,

Supports multi-line input now. Halts in an error, which is allowed by default

Try it Online!

\$\endgroup\$
1
  • \$\begingroup\$ fixed (padding) \$\endgroup\$ – EdgyNerd Aug 24 '19 at 14:26
3
\$\begingroup\$

Gol><>, 2 bytes

credit to Jo King

io

Try it online!

Errors out on EOF. The error message goes to stderr.

How it works

io

i   Push an input char
 o  Pop and print; error if last input hit EOF
    Repeat indefinitely

Gol><>, 4 bytes

iE;o

Try it online!

No-error version.

How it works

iE;o

i     Push an input char
 E;   Halt on EOF
   o  Pop and print
      Repeat indefinitely
\$\endgroup\$
0
3
\$\begingroup\$

C, 17, 16 bytes

main(){tee(0,1);}

This only works on certain compilers (such as tutorialspoint which uses GCC), but it's really short.

main(){tee(1j);}

Edit: Now down to 16 bytes! j is a GNU suffix which acts as a complex
number. Basically tee(1j) == tee(0,1). This trick also only works in rare cases.

\$\endgroup\$
3
\$\begingroup\$

MAWP, 7 bytes

|0~[;].

Try it!

Explanation:

|      Push input to stack
0      Add a zero to stack
~      Reverse stack
[;]    Output each character from stack until 0
.      Terminate program
\$\endgroup\$
3
\$\begingroup\$

vJASS (Warcraft 3), 202 181 bytes

Using //! import zinc "<code_path>" command to exclude //! zinc and //! endzinc.


library a{trigger t=CreateTrigger();function onInit(){TriggerRegisterPlayerChatEvent(t,Player(0),"",false);TriggerAddAction(t,function(){BJDebugMsg(GetEventPlayerChatString());});}}

Readable Version:

library a{
   trigger t = CreateTrigger();

   function onInit(){
      // Create an INPUT EVENT
      TriggerRegisterPlayerChatEvent(t, Player(0), "", false);
      TriggerAddAction(t, function(){BJDebugMsg(GetEventPlayerChatString());});
   }
}
\$\endgroup\$
3
+100
\$\begingroup\$

, 5 bytes

No interpreter yet, but:

#@$,*

When unfolded into a cube, it adds a no-op:

  #
@ $ , *
  .

The IP starts in the top cell (#) and "falls" downwards, into the $. I'll try to explain the code the best I can (which is not very well):

#   Later acts as "ground," not letting the IP pass through it. However, the IP checks for ground AFTER running commands, so '#' does nothing here.
    (The IP falls downwards after running each command.)
$   Ignores the next command if the current memory cell is 0. The memory cells all start at 0, and since the memory has not been changed at all, it ignores the next command.
.   No-op, does not count as command.
    (If the IP goes out of the area, it goes to a corresponding cell and rotates its direction and , as if the code were written on the faces of a cube.)
*   Prints the output from the current memory cell. However, this is not run, because '$' ignored this command.
    (If the IP falls or moves into '#', it snaps back to its previous position and moves in its given direction. It starts facing right, however after leaving the cube's map, it now faces left, so the IP now moves left and continues to do this for the rest of the program's runtime.)

,   ("Actual" start of program) Inputs next ASCII character in input to the current memory cell.
$   Ignores next command if the end has been reached (EOF returns 0).
@   Terminates the program if the end has been reached.
*   Output ASCII character from the current memory cell.

(Program continues from last ',')

I don't think it's possible to golf it into 4 bytes, but I hope I'm wrong.

\$\endgroup\$
7
  • \$\begingroup\$ Looks like an interesting language! Did you make it? \$\endgroup\$ – Redwolf Programs Jan 22 at 21:38
  • 1
    \$\begingroup\$ @RedwolfPrograms Yep :) It's basically a mix between MarioLANG and Cubix. \$\endgroup\$ – Bo_Tie Jan 23 at 22:26
  • \$\begingroup\$ If you write an interpreter make sure to let me know, as this (or another) answer will be able to receive a bounty! \$\endgroup\$ – Redwolf Programs Jan 23 at 22:45
  • \$\begingroup\$ @RedwolfPrograms Made an interpreter! repl.it/@BoTie/v3-Interpreter#script.txt \$\endgroup\$ – Bo_Tie Feb 3 at 18:20
  • \$\begingroup\$ Looks really cool! Definitely deserves the bounty. Let me know if you want it on this answer, or if you think a different one would show off more of the features! \$\endgroup\$ – Redwolf Programs Feb 3 at 18:25
2
\$\begingroup\$

C--, 171 bytes

target byteorder little;import getchar,putchar;export main;foreign"C"main(){t:bits32 v;v=foreign "C" getchar();if(v!=-1){foreign"C"putchar(v);goto t;}foreign"C"return(0);}

Considering C-- is essentially a "portable assembler", I shouldn't be surprised that this was huge.

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2
\$\begingroup\$

Befunge-98, 4 bytes

#@~,

The program counter starts moving to the right in the top-left corner of the program. # causes it to jump over @, landing on ~. This reads a character, or reflects the PC on EOF. If EOF is reached, this will cause it to run into @, which ends the program. Otherwise, it continues to ,, which prints the character that was read, and loops back to # thanks to Lahey-space.

\$\endgroup\$
3
  • \$\begingroup\$ Is the reflect-on-EOF behavior in the spec? I didn't know about it before. (Then again, I coded mostly in Befunge-93.) \$\endgroup\$ – El'endia Starman Oct 30 '15 at 16:52
  • \$\begingroup\$ Yeah: In the case of an end-of-file or other file error condition, the & and ~ both act like r. \$\endgroup\$ – Lynn Oct 30 '15 at 16:53
  • \$\begingroup\$ Huh, interesting. The lack of this behavior in Befunge-93 added five bytes! Doubled the program length! \$\endgroup\$ – El'endia Starman Oct 30 '15 at 16:54
2
\$\begingroup\$

Python 3, 50 bytes

import sys
while 1:print(sys.stdin.read(1),end='')

See comment in my python 2 answer about newlines.

OR 29 bytes

while 1:print(input())

Waits explicitly for newlines before printing. (This means that it won't print anything after a newline before the next)

\$\endgroup\$
4
  • 1
    \$\begingroup\$ Adds trailing newline. \$\endgroup\$ – feersum Oct 30 '15 at 16:42
  • \$\begingroup\$ Can't you do print(end=sys.stdin.read(1))? \$\endgroup\$ – Erik the Outgolfer Sep 27 '16 at 17:52
  • \$\begingroup\$ I've found a shorter one using os.read/write and fd numbers, it is 42 bytes. tio.run/##K6gsycjPM/7/… \$\endgroup\$ – Rick Rongen Dec 28 '18 at 18:23
  • \$\begingroup\$ Feel free to post it yourself and take the credit for it^^ \$\endgroup\$ – Blue Dec 28 '18 at 18:32
2
\$\begingroup\$

Pyth, 28 bytes

V$__import__('sys').stdin$pN

Not as short as @Mauris's Pyth answer, but it handles infinite input.

\$\endgroup\$
2
\$\begingroup\$

Erlang, 108 Bytes

Uses escript to run. Making the code a one-liner seems to cause an EOF error from the interpreter.

#!/usr/bin/env escript
main(_)->f(a).
f(eof)->ok;f([C])->f(io:format("~c",[C]));f(_)->f(io:get_chars('',1)).
\$\endgroup\$
2
\$\begingroup\$

lua for windows, 38 bytes

Needs lua for windows

while true do io.write(io.read()) end

how it works

It prints the input from the terminal

\$\endgroup\$
1
  • \$\begingroup\$ You can make it shorter using a true condition _G (the global table) and removing the space after the last brace. \$\endgroup\$ – Jairo A. del Rio Jan 23 at 2:25
2
\$\begingroup\$

Julia, 45 bytes

while !eof(STDIN) print(read(STDIN,Char))end

Ungolfed + explanation:

while !eof(STDIN)             # While EOF has not been encountered from STDIN
    r = read(STDIN, Char)     # Read a single character from STDIN
    print(r)                  # Print it to STDOUT with no trailing anything
end

This supports an infinite input stream and null bytes and has no extraneous output.

Thanks to Dennis and Martin Büttner for their help on this!

\$\endgroup\$
0
2
\$\begingroup\$

D, 94 bytes

import std.stdio,std.algorithm;void main(){stdin.byChunk(1).copy(stdout.lockingTextWriter());}

I'm no D expert at all, so there might be a better way to do this.

\$\endgroup\$
1
  • \$\begingroup\$ I don't think you need the parens after stdout.lockingTextWriter. \$\endgroup\$ – Adalynn Nov 26 '16 at 17:53
2
\$\begingroup\$

QBasic, 15 bytes

?INPUT$(1);
RUN

QBasic doesn't have any concept of input or output streams (except maybe where files are concerned). The above program instead takes any character you enter and echoes it to the screen, which I think fits the spirit of the challenge. RUN restarts the program from scratch, thus continuing to read and echo forever (there's no EOF for keyboard input, and I don't think it's even possible to enter a null byte).

Here's a 34-byte version that quits when you press escape. The should be replaced with a literal Esc character, ASCII 27. This can be entered in the QBasic editor by holding the Alt key while typing the character code; it shows up as a .

9?x$;
x$=INPUT$(1)
IF"…"<>x$THEN 9
\$\endgroup\$
2
\$\begingroup\$

TECO, 4 bytes

<^T^T>

^T is CTRL+T. It should be self-explanatory how this works.

For those of you who can't read this infamously write-only language, it simply loops over the input (<>), reading (^T) and immediately printing (^T) bytes.

\$\endgroup\$
2
\$\begingroup\$

PHP, 20 bytes

<? fpassthru(STDIN);

Kind of surprised there isn't one for PHP yet...

\$\endgroup\$
2
  • \$\begingroup\$ I bet you can get rid of the space. \$\endgroup\$ – Lynn Oct 31 '15 at 12:09
  • 1
    \$\begingroup\$ Run it with -r and you can get rid of the opening tag altogether. echo -e "Hello\nWorld" | php -r 'fpassthru(STDIN);' 17 bytes \$\endgroup\$ – aross Mar 18 '16 at 10:51
2
\$\begingroup\$

Emmental, 20 bytes

;#44#46#35#57#63#9!<tab>

The program ends with a tab character. This beats the example on the wiki page by redefining and invoking the tab character (ASCII 9) instead of the asterisk (ASCII 42). The spec doesn't really mention what , does at EOF, but the reference implementation uses getChar, which raises an IOError when the file ends. (The , is "quoted" as #44 in the above program.)

\$\endgroup\$
0
2
\$\begingroup\$

ngn APL, 7 bytes

{∇⍞←⍞}1

ngn APL only supports linewise input and has no actual looping constructs, so this recursive function is as good as it gets. It prints null bytes, but only if they do not occur on the last line.

How it works

{    }   Define a function.
  ⍞←⍞    Read and print a line.
 ∇       Call the function again.
      1  Call the function with dummy input.

exits automatically on EOF.

\$\endgroup\$
2
  • \$\begingroup\$ There is the looping construct . It's just not so procedural. \$\endgroup\$ – jimmy23013 Nov 1 '15 at 23:51
  • \$\begingroup\$ I haven't been able to get working for this task. Anyway, -⍣≡1 leaks memory, so the result would probably be the same. \$\endgroup\$ – Dennis Nov 2 '15 at 4:44
2
\$\begingroup\$

Java, 120 bytes

The other Java solution is shorter than mine but, it uses Apache libraries to get the job done. I think it's worthwhile to put forward a java solution that relies solely on the java standard libraries.

This code works for infinite input and for input that contains null bytes.

class C{public static void main(String[]a)throws Exception{byte[]b={0};while(System.in.read(b)>=0)System.out.write(b);}}

Ungolfed

import java.io.IOException;

public class Cat {
  public static void main(String[] args) throws IOException {
    byte[] input=new byte[1];
    while(System.in.read(input)>=0){
      System.out.write(input);
    }
  }
}
\$\endgroup\$
4
  • \$\begingroup\$ You don't need public in the class declaration. You can just throw Exception instead of IOException and not have to import anything in the Ungolfed version. \$\endgroup\$ – Addison Crump Nov 2 '15 at 11:35
  • \$\begingroup\$ Using the stderr rule, you could abuse an enum: enum C{C;System z;{try{byte[]b={0};while(z.in.read(b)>=0)z.out.write(b);}catch(Exception e){}}} \$\endgroup\$ – ninjalj Nov 2 '15 at 20:16
  • \$\begingroup\$ @ninjalj I can't figure out how to get the compiled class to execute the code block without loading the class from some other program. Is there anyway to execute it from the command line? \$\endgroup\$ – ankh-morpork Nov 2 '15 at 21:09
  • \$\begingroup\$ @dohaqatar7: java -classpath <wherever> C should work. \$\endgroup\$ – ninjalj Nov 2 '15 at 21:16
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Groovy, 39 bytes

System.in.eachByte{System.out.write it}

Since I wrote a proof-of-concept to confirm that Groovy can handle infinite stream, might as well post it as an answer.

Usage:

groovy <script_name>
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Emotinomicon, 29 bytes

⏪⏫🆙⏬😅➕⁉️⏩

Most of the program is just checking for EOF.

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LabVIEW, 3 LabVIEW Primitives

Pretty obvious what it does I would say.

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PlatyPar, 0 bytes

 

Try it online

At the beginning of the program, input is implicitly pushed to the stack. At the end of the program, the stack is implicitly printed.

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