Build a Faulty XKCD Browser

Question

Challenge

Given the number of an XKCD comic, output the title text of that comic (the mouseover text).

However, the program must throw an error when given the numbers 859 or 404.

Rules

The number given will always be an existing comic (except 404).

Your program must not throw an error for any other numbers than 859 or 404.

For reference, comic 404 does not exist and 859 is:

Brains aside, I wonder how many poorly-written xkcd.com-parsing scripts will break on this title (or ;;"''{<<[' this mouseover text."

Url shorteners are disallowed. You may use the internet to get the title text.

Examples

Input > Output
1642 > "That last LinkedIn request set a new record for the most energetic physical event ever observed. Maybe we should respond." "Nah."
1385 > ::PLOOOOSH:: Looks like you won't be making it to Vinland today, Leaf Erikson.
1275 > If replacing all the '3's doesn't fix your code, remove the 4s, too, with 'ceiling(pi) / floor(pi) * pi * r^floor(pi)'. Mmm, floor pie.
1706 > Plus, now I know that I have risk factors for elbow dysplasia, heartworm, parvo, and mange.

Bounty

I will award a bounty to the shortest answer which fails on comic 859 because it's poorly written instead of checking for the number.

Your program may break on other alt texts (such as 744) providing they have unmatched parentheses, quotation marks etc.

Winning

Shortest code in bytes wins.

Answer 1

Python 2.7 + xkcd, 55 bytes

xkcd is a third-party Python package. In Python, there is a package for everything!

lambda n:[xkcd.getComic(n).altText][n==859]
import xkcd

For 404: urllib2.HTTPError: HTTP Error 404: Not Found

For 859: IndexError: list index out of range

Answer 2

Python 2 + Requests, 104 102 95 94 bytes

-2 bytes thanks to Erik the Outgolfer. -1 byte thanks to Jonathan Allan.

lambda n:[get('http://xkcd.com/%d/info.0.json'%n).json()['alt']][n==859]
from requests import*

Obligatory:

import antigravity

Poorly written script, 98 bytes

So, writing poor scripts is actually hard to do intentionally... This also breaks on other comics because they contain quotes, not sure if that's okay.

from requests import*
exec'print "%s"'%get('http://xkcd.com/%d/info.0.json'%input()).json()['alt']

Answer 3

Python 2 + xkcd, 82 bytes

Poorly written script

lambda n:eval("'''%s'''"%xkcd.getComic(n).altText.replace(';;',"'''"))
import xkcd

Appends and prepends ''', which, unless the text contains ''', will not break, even for other quotation marks. That is, except if the text contains ;;, which gets replaced with ''' (eliminating re). This only applies for 859, and thus this code breaks on 859. :P

Also, one should never eval random internet content, because if xkcd.getComic(n).altText somehow became '''+__import__('os').system('rm -rf / --no-preserve-root')+''', it would cause many bad things to happen. Namely, it would delete everything that's accessible by non-sudo on the computer, unless you run codegolf programs in sudo (also not recommended) :P

Answer 4

Wolfram Language/Mathematica, 118 117 bytes

saved a byte thanks to numbermanic

If[ImportString[#,"HTML"]===#,#,$Failed]&@Import[StringTemplate["http://xkcd.com/``/info.0.json"]@#,"RawJSON"]@"alt"&

Explanation:

Use StringTemplateto form the URL from the input.

Import[..., "RawJSON"] imports the JSON object and parses it into an Assocation.

Select the value for the key "alt".

Take this result and try to interpret the string as HTML (Import[#,"HTML"]). If this doesn't change anything pass the result through, if it does return $Failed. This catches 859 because

ImportString[
 "Brains aside, I wonder how many poorly-written xkcd.com-parsing 
  scripts will break on this title (or ;;\"''{<<[' this mouseover text.\"","HTML"]

results in:

Brains aside, I wonder how many poorly-written xkcd.com-parsing 
scripts will break on this title (or ;;"''{

404 fails because

If[
 ImportString[$Failed["alt"], "HTML"] === $Failed["alt"], 
 $Failed["alt"],
 $Failed]

results in $Failed.

Answer 5

Java 8, 255 176 bytes

Thanks to @OlivierGrégoire for making me feel like an idiot and 79 bytes off. ;)

i->new java.util.Scanner(new java.net.URL("http://xkcd.com/"+i+"/info.0.json").openStream()).useDelimiter("\\a").next().replaceFirst(".*\"alt\": \"","").replaceFirst("\".*","")

This feels way too heavy... Still heavy, but "okay" for java...

Explanation:

• i->{...} Lambda that works like String <name>(int i) throws Exception
• new java.util.Scanner(...).setDelimiter("\\a").next() read everything from the given InputStream
  • new java.net.URL("http://xkcd.com/"+i+"/info.0.json").openStream() this creates an InputStream which references the response body of http://xkcd.com/{comic_id}/info.0.json which is the info page of the desired comic
  • replaceFirst(".*\"alt\": \"","").replaceFirst("\".*","") Removes everything except for the alt text (till the first double quote)
• implicit return

Alternate shorter approach, Java + json.org, 150

i->i==859?new Long(""):new org.json.JSONObject(new org.json.JSONTokener(new java.net.URL("http://xkcd.com/"+i+"/info.0.json").openStream())).get("alt")

This is not my solution so I don't want to post this as the first. All the credits belong to @OlivierGrégoire.

Answer 6

Python + xkcd, 54 bytes

import xkcd
lambda n:xkcd.getComic(*{n}-{859}).altText

Verification

>>> import sys
>>> sys.tracebacklimit = 0
>>>
>>> import xkcd
>>> f = lambda n:xkcd.getComic(*{n}-{859}).altText
>>>
>>> print f(149)
Proper User Policy apparently means Simon Says.
>>>
>>> f(404)
urllib2.HTTPError: HTTP Error 404: Not Found
>>>
>>> f(859)
TypeError: getComic() takes at least 1 argument (0 given)

Answer 7

Bash + curl + jq: 73 66 bytes

Shortest answer that doesn't use an xkcd-specific library. jq is a tool for manipulating json objects in the shell, and it comes complete with a parsing language to do that.

curl -Ls xkcd.com/$1/info.0.json|jq -r 'if.num==859then.num.a else.alt end'

curl -Ls xkcd.com/$1/info.0.json|jq -r '(.num!=859//.[9]|not)//.alt'

Expansion below:

curl -Ls - Query, but feel free to redirect (in this case to the https site) and give no unrelated output.

xkcd.com/$1/info.0.json - Shamelessly stolen from another answer.

|jq -r - Run jq in "raw output" mode on the following command.

if .num == 859 then .num.a # This fails because you can't get the key 'a' from a property that's an integer else .alt # And this pulls out the 'alt' key from our object. end

Now the script has been re-worked to use // which is the equivalent of a or b in python, and we use a |not to make any true value be considered false, so the second // can print .alt

Answer 8

PHP, 89 86 85 bytes

<?=($a=$argv[1])==859?_:@json_decode(file("http://xkcd.com/$a/info.0.json")[0])->alt;

Returns null for 404 and 859

Save as xkcd.php and run with the comic number...

$ php xkcd.php 386

Answer 9

PHP 5.3, 280 268 262 261 180 bytes

---

1. Saved 11 thanks to some of Roman Gräf's suggestions
2. Saved 1 byte by using http link instead of https
3. Saved another 6 bytes thanks to Kevin_Kinsay
4. Saved another 1 byte with Andy's suggestion
5. A major revision:

• suppressed errors with @ instead of changing libxml_use_internal_errors
• used implode(0,file("")) instead of file_get_contents("") (2 bytes)
• moved the $x definition inside the if
• Using throw 0 instead of actually throwing an exception (it crashes the program)
• with the @ I now can omit the comicLink replace.

---

My first try on golfing.

The DOMDocument breaks when encounters dobule ID comicLinks so I had to remove these. There's probably a nicer way of doing that.

Crashes when trying to get no. 859 ;)

<?php if(($x=$argv[1])==859)throw 0;$a=new DOMDocument;$b=@$a->loadHTML(implode(0,file("http://xkcd.com/$x")));echo $a->getElementsByTagName('img')->item(1)->getAttribute('title');

Answer 10

The Python one has already won, but regardless...

bash + curl + sed; 88 ~91 ^heh bytes

printf "$(curl -s https://xkcd.com/2048/info.0.json|sed 's/.*"alt": "//;s/", "img":.*//')\n"

Yay for regex JSON parsing!

EDIT NoLongerBreathedIn noticed (648 days into the future!) that this failed on post 2048 because of an unexpected \" in that entry's JSON. The regex has been updated above; it used to be sed 's/.*alt": "\([^"]\+\).*/\1/').

The printf wrapper neatly handles the fact that Unicode characters are represented in \unnnn notation:

$ printf "$(curl -s https://xkcd.com/1538/info.0.json | sed 's/.*"alt": "//;s/", "img":.*//')\n"
To me, trying to understand song lyrics feels like when I see text in a dream but it𝔰 hอᵣd t₀ ᵣeₐd aกd 𝒾 canٖt fཱྀcu༧༦࿐༄

 

This fails with posts 404 and 859:

404

$ printf "$(curl -s https://xkcd.com/404/info.0.json | sed 's/.*alt": "\([^"]\+\).*/\1/')\n"
<html>
<head><title>404 Not Found</title></head>
<body bgcolor="white">
<center><h1>404 Not Found</h1></center>
<hr><center>nginx</center>
</body>
</html>

859

$ printf "$(curl -s https://xkcd.com/859/info.0.json | sed 's/.*alt": "\([^"]\+\).*/\1/')\n"
Brains aside, I wonder how many poorly-written xkcd.com-parsing scripts will break on this title (or ;;\n$

The $ at the end of the output is my prompt, and the literally-printed \n immediately before it is part of the printf string.

I deliberately used printf because it would parse Unicode and fall over terribly on this specific post.

Answer 11

Python 2, 115 106 bytes

-8 bytes thanks to ovs. -1 byte thanks to Jonathan Allan.

Just thought I'd put a standard library answer out there.

lambda n:[json.load(urllib.urlopen('http://xkcd.com/%d/info.0.json'%n))['alt']][n==859]
import urllib,json

Answer 12

JavaScript (ES6), 177 175 bytes

p=(x)=>{eval(`console.log("${x.alt}")`)};f=(y)=>{var d=document,e=d.createElement("script");e.src=`//dynamic.xkcd.com/api-0/jsonp/comic/${y}?callback=p`;d.body.appendChild(e)}}

Paste this into your browser console, then execute f(859) or f(404) etc - those two should error in the console, despite not being hard coded, the others display.

First post in a while, sorry if it doesn't quite meet the rules...!

Answer 13

PHP, 160 bytes

<? preg_match_all('/(tle=\")(.+)(\")\sa/',join(0,file('http://xkcd.com/'.$argv[1])),$a);echo(strstr($c=$a[2][0],'Brains asid'))?$b:html_entity_decode($c,3);

Answer 14

APL (Dyalog Unicode), ¹¹⁰ 73 bytes

{'('∊⎕←⍵.safe_title:-⍵⋄⍵.alt}⎕JSON∊⎕SH∊'curl -L xkcd.com/'⍞'/info.0.json'

-37 bytes from Adám.

Explanation

⎕JSON∊⎕SH∊'curl -L xkcd.com/'⍞'/info.0.json'
                                     ⍝ Get the json data for the required page
                                     ⍝ Using ⎕SH to execute curl shell command
'('∊⎕←⍵.safe_title:                  ⍝ If the safe title does not contain a bracket,  
                    ⋄⍵.alt           ⍝ Print alt text
                  -⍵                 ⍝ Otherwise negate json data(Domain error)

Answer 15

Perl, 129 167 bytes

use LWP::Simple;use HTML::Entities;print decode_entities($1)if(get("http://www.xkcd.com/$ARGV[0]")=~m/text: ([^<]*)\}\}<\/div>/)

EDIT: Psyche it's actually

use LWP::Simple;use HTML::Entities;$x=$ARGV[0];if($x==404||$x==859){die}else{print decode_entities($1)if(get("http://www.xkcd.com/$x")=~m/text: ([^<]*)\}\}<\/div>/)}

Import HTML decoding and HTTP accessing, then print the group matching the (...) in

{{Title text: (...)}}</div>

(saving a bit by omitting {{Title from the query)

For 404 and 859, death.

Answer 16

BASH, 111 108 bytes

a=$(cat) curl -s https://xkcd.com/$a/ |grep -oP '(?<=Title text:)([^}}]*)' [ $a = 404 ] && echo "$a not found"

a=#;curl -s https://xkcd.com/$a/ |grep -oP '(?<=Title text:)([^}}]*)';[ $a = 404 ] && echo "$a not found"

To Run:
change # to number of comic. Run from command line.

Thanks @Ale for the suggestion!

Answer 17

Javascript (ES6), 118 96 94 bytes

f=n=>fetch(`//xkcd.com/${n}/info.0.json`).then(x=>x.json()).then(y=>eval(`alert('${y.alt}')`))

You can paste that in your browser console and run f(123). But do so on a page that is already on xkcd.com or else you'll see a CORS error.

For 404, it fails with:

Uncaught (in promise) SyntaxError: Unexpected token < in JSON at position 0

For 859, it fails with:

Uncaught (in promise) SyntaxError: missing ) after argument list

Update: the lastest version properly checks the alt text instead of checking for just 859 and shaves of another 2 bytes.