HTML: Parsing Library

8.15

HTML: Parsing Library🔗ℹ

The html library provides functions to read conformant HTML4 documents and structures to represent them. Since html assumes documents are conformant and is restricted to the older specific, it should be viewed as a legacy library. We suggest using the html-parsing package for modern Web scraping.

procedure
(read-xhtml port) → html?
port : input-port?
procedure
(read-html port) → html?
port : input-port?

Reads (X)HTML from a port, producing an html instance.

procedure
(read-html-as-xml port) → (listof content/c)
port : input-port?

Reads HTML from a port, producing a list of XML content, each of which could be turned into an X-expression, if necessary, with xml->xexpr.

parameter
(read-html-comments) → boolean?
(read-html-comments v) → void?
v : any/c

If v is not #f, then comments are read and returned. Defaults to #f.

parameter
(use-html-spec) → boolean?
(use-html-spec v) → void?
v : any/c

If v is not #f, then the HTML must respect the HTML specification with regards to what elements are allowed to be the children of other elements. For example, the top-level "<html>" element may only contain a "<body>" and "<head>" element. Defaults to #t.

1 Example🔗ℹ

(module html-example racket

 ; Some of the symbols in html and xml conflict with
 ; each other and with racket/base language, so we prefix
 ; to avoid namespace conflict.
 (require (prefix-in h: html)
 (prefix-in x: xml))

 (define an-html
 (h:read-xhtml
 (open-input-string
 (string-append
 "<html><head><title>My title</title></head><body>"
 "Hello worldTesting!"
 "</body></html>"))))

 ; extract-pcdata: html-content/c -> (listof string)
 ; Pulls out the pcdata strings from some-content.
 (define (extract-pcdata some-content)
 (cond [(x:pcdata? some-content)
 (list (x:pcdata-string some-content))]
 [(x:entity? some-content)
 (list)]
 [else
 (extract-pcdata-from-element some-content)]))

 ; extract-pcdata-from-element: html-element -> (listof string)
 ; Pulls out the pcdata strings from an-html-element.
 (define (extract-pcdata-from-element an-html-element)
 (match an-html-element
 [(struct h:html-full (attributes content))
 (apply append (map extract-pcdata content))]

 [(struct h:html-element (attributes))
 '()]))

 (printf "~s\n" (extract-pcdata an-html)))

> (require 'html-example)
("My title" "Hello world" "Testing" "!")

2 HTML Structures🔗ℹ

pcdata, entity, and attribute are defined in the xml documentation.

value
html-content/c : contract?

A html-content/c is either

struct
(struct html-element (attributes)
#:extra-constructor-name make-html-element)
attributes : (listof attribute)

Any of the structures below inherits from html-element.

struct
(struct html-full struct:html-element (content)
#:extra-constructor-name make-html-full)
content : (listof html-content/c)

Any html tag that may include content also inherits from html-full without adding any additional fields.

struct
(struct mzscheme html-full ()
#:extra-constructor-name make-mzscheme)

A mzscheme is special legacy value for the old documentation system.

struct
(struct html html-full ()
#:extra-constructor-name make-html)

A html is (make-html (listof attribute) (listof Contents-of-html))

A Contents-of-html is either

body
head

struct
(struct div html-full ()
#:extra-constructor-name make-div)

A div is (make-div (listof attribute) (listof G2))

struct
(struct center html-full ()
#:extra-constructor-name make-center)

A center is (make-center (listof attribute) (listof G2))

struct
(struct blockquote html-full ()
#:extra-constructor-name make-blockquote)

A blockquote is (make-blockquote (listof attribute) (listof G2))

struct
(struct ins html-full ()
#:extra-constructor-name make-ins)

An Ins is (make-ins (listof attribute) (listof G2))

struct
(struct del html-full ()
#:extra-constructor-name make-del)

A del is (make-del (listof attribute) (listof G2))

struct
(struct dd html-full ()
#:extra-constructor-name make-dd)

A dd is (make-dd (listof attribute) (listof G2))

struct
(struct li html-full ()
#:extra-constructor-name make-li)

A li is (make-li (listof attribute) (listof G2))

struct
(struct th html-full ()
#:extra-constructor-name make-th)

A th is (make-th (listof attribute) (listof G2))

struct
(struct td html-full ()
#:extra-constructor-name make-td)

A td is (make-td (listof attribute) (listof G2))

struct
(struct iframe html-full ()
#:extra-constructor-name make-iframe)

An iframe is (make-iframe (listof attribute) (listof G2))

struct
(struct noframes html-full ()
#:extra-constructor-name make-noframes)

A noframes is (make-noframes (listof attribute) (listof G2))

struct
(struct noscript html-full ()
#:extra-constructor-name make-noscript)

A noscript is (make-noscript (listof attribute) (listof G2))

struct
(struct style html-full ()
#:extra-constructor-name make-style)

A style is (make-style (listof attribute) (listof pcdata))

struct
(struct script html-full ()
#:extra-constructor-name make-script)

A script is (make-script (listof attribute) (listof pcdata))

struct
(struct basefont html-element ()
#:extra-constructor-name make-basefont)

A basefont is (make-basefont (listof attribute))

struct
(struct br html-element ()
#:extra-constructor-name make-br)

A br is (make-br (listof attribute))

struct
(struct area html-element ()
#:extra-constructor-name make-area)

An area is (make-area (listof attribute))

struct
(struct alink html-element ()
#:extra-constructor-name make-alink)

A alink is (make-alink (listof attribute))

struct
(struct img html-element ()
#:extra-constructor-name make-img)

An img is (make-img (listof attribute))

struct
(struct param html-element ()
#:extra-constructor-name make-param)

A param is (make-param (listof attribute))

struct
(struct hr html-element ()
#:extra-constructor-name make-hr)

A hr is (make-hr (listof attribute))

struct
(struct input html-element ()
#:extra-constructor-name make-input)

An input is (make-input (listof attribute))

struct
(struct col html-element ()
#:extra-constructor-name make-col)

A col is (make-col (listof attribute))

struct
(struct isindex html-element ()
#:extra-constructor-name make-isindex)

An isindex is (make-isindex (listof attribute))

struct
(struct base html-element ()
#:extra-constructor-name make-base)

A base is (make-base (listof attribute))

struct
(struct meta html-element ()
#:extra-constructor-name make-meta)

A meta is (make-meta (listof attribute))

struct
(struct option html-full ()
#:extra-constructor-name make-option)

An option is (make-option (listof attribute) (listof pcdata))

struct
(struct textarea html-full ()
#:extra-constructor-name make-textarea)

A textarea is (make-textarea (listof attribute) (listof pcdata))

struct
(struct title html-full ()
#:extra-constructor-name make-title)

A title is (make-title (listof attribute) (listof pcdata))

struct
(struct head html-full ()
#:extra-constructor-name make-head)

A head is (make-head (listof attribute) (listof Contents-of-head))

A Contents-of-head is either

base
isindex
alink
meta
object
script
style
title

struct
(struct tr html-full ()
#:extra-constructor-name make-tr)

A tr is (make-tr (listof attribute) (listof Contents-of-tr))

A Contents-of-tr is either

struct
(struct colgroup html-full ()
#:extra-constructor-name make-colgroup)

A colgroup is (make-colgroup (listof attribute) (listof col))

struct
(struct thead html-full ()
#:extra-constructor-name make-thead)

A thead is (make-thead (listof attribute) (listof tr))

struct
(struct tfoot html-full ()
#:extra-constructor-name make-tfoot)

A tfoot is (make-tfoot (listof attribute) (listof tr))

struct
(struct tbody html-full ()
#:extra-constructor-name make-tbody)

A tbody is (make-tbody (listof attribute) (listof tr))

struct
(struct tt html-full ()
#:extra-constructor-name make-tt)

A tt is (make-tt (listof attribute) (listof G5))

struct
(struct i html-full ()
#:extra-constructor-name make-i)

An i is (make-i (listof attribute) (listof G5))

struct
(struct b html-full ()
#:extra-constructor-name make-b)

A b is (make-b (listof attribute) (listof G5))

struct
(struct u html-full ()
#:extra-constructor-name make-u)

An u is (make-u (listof attribute) (listof G5))

struct
(struct s html-full ()
#:extra-constructor-name make-s)

A s is (make-s (listof attribute) (listof G5))

struct
(struct strike html-full ()
#:extra-constructor-name make-strike)

A strike is (make-strike (listof attribute) (listof G5))

struct
(struct big html-full ()
#:extra-constructor-name make-big)

A big is (make-big (listof attribute) (listof G5))

struct
(struct small html-full ()
#:extra-constructor-name make-small)

A small is (make-small (listof attribute) (listof G5))

struct
(struct em html-full ()
#:extra-constructor-name make-em)

An em is (make-em (listof attribute) (listof G5))

struct
(struct strong html-full ()
#:extra-constructor-name make-strong)

A strong is (make-strong (listof attribute) (listof G5))

struct
(struct dfn html-full ()
#:extra-constructor-name make-dfn)

A dfn is (make-dfn (listof attribute) (listof G5))

struct
(struct code html-full ()
#:extra-constructor-name make-code)

A code is (make-code (listof attribute) (listof G5))

struct
(struct samp html-full ()
#:extra-constructor-name make-samp)

A samp is (make-samp (listof attribute) (listof G5))

struct
(struct kbd html-full ()
#:extra-constructor-name make-kbd)

A kbd is (make-kbd (listof attribute) (listof G5))

struct
(struct var html-full ()
#:extra-constructor-name make-var)

A var is (make-var (listof attribute) (listof G5))

struct
(struct cite html-full ()
#:extra-constructor-name make-cite)

A cite is (make-cite (listof attribute) (listof G5))

struct
(struct abbr html-full ()
#:extra-constructor-name make-abbr)

An abbr is (make-abbr (listof attribute) (listof G5))

struct
(struct acronym html-full ()
#:extra-constructor-name make-acronym)

An acronym is (make-acronym (listof attribute) (listof G5))

struct
(struct sub html-full ()
#:extra-constructor-name make-sub)

A sub is (make-sub (listof attribute) (listof G5))

struct
(struct sup html-full ()
#:extra-constructor-name make-sup)

A sup is (make-sup (listof attribute) (listof G5))

struct
(struct span html-full ()
#:extra-constructor-name make-span)

A span is (make-span (listof attribute) (listof G5))

struct
(struct bdo html-full ()
#:extra-constructor-name make-bdo)

A bdo is (make-bdo (listof attribute) (listof G5))

struct
(struct font html-full ()
#:extra-constructor-name make-font)

A font is (make-font (listof attribute) (listof G5))

struct
(struct p html-full ()
#:extra-constructor-name make-p)

A p is (make-p (listof attribute) (listof G5))

struct
(struct h1 html-full ()
#:extra-constructor-name make-h1)

A h1 is (make-h1 (listof attribute) (listof G5))

struct
(struct h2 html-full ()
#:extra-constructor-name make-h2)

A h2 is (make-h2 (listof attribute) (listof G5))

struct
(struct h3 html-full ()
#:extra-constructor-name make-h3)

A h3 is (make-h3 (listof attribute) (listof G5))

struct
(struct h4 html-full ()
#:extra-constructor-name make-h4)

A h4 is (make-h4 (listof attribute) (listof G5))

struct
(struct h5 html-full ()
#:extra-constructor-name make-h5)

A h5 is (make-h5 (listof attribute) (listof G5))

struct
(struct h6 html-full ()
#:extra-constructor-name make-h6)

A h6 is (make-h6 (listof attribute) (listof G5))

struct
(struct q html-full ()
#:extra-constructor-name make-q)

A q is (make-q (listof attribute) (listof G5))

struct
(struct dt html-full ()
#:extra-constructor-name make-dt)

A dt is (make-dt (listof attribute) (listof G5))

struct
(struct legend html-full ()
#:extra-constructor-name make-legend)

A legend is (make-legend (listof attribute) (listof G5))

struct
(struct caption html-full ()
#:extra-constructor-name make-caption)

A caption is (make-caption (listof attribute) (listof G5))

struct
(struct table html-full ()
#:extra-constructor-name make-table)

A table is (make-table (listof attribute) (listof Contents-of-table))

A Contents-of-table is either

caption
col
colgroup
tbody
tfoot
thead

struct
(struct button html-full ()
#:extra-constructor-name make-button)

A button is (make-button (listof attribute) (listof G4))

struct
(struct fieldset html-full ()
#:extra-constructor-name make-fieldset)

A fieldset is (make-fieldset (listof attribute) (listof Contents-of-fieldset))

A Contents-of-fieldset is either

legend
G2

struct
(struct optgroup html-full ()
#:extra-constructor-name make-optgroup)

An optgroup is (make-optgroup (listof attribute) (listof option))

struct
(struct select html-full ()
#:extra-constructor-name make-select)

A select is (make-select (listof attribute) (listof Contents-of-select))

A Contents-of-select is either

optgroup
option

struct
(struct label html-full ()
#:extra-constructor-name make-label)

A label is (make-label (listof attribute) (listof G6))

struct
(struct form html-full ()
#:extra-constructor-name make-form)

A form is (make-form (listof attribute) (listof G3))

struct
(struct ol html-full ()
#:extra-constructor-name make-ol)

An ol is (make-ol (listof attribute) (listof li))

struct
(struct ul html-full ()
#:extra-constructor-name make-ul)

An ul is (make-ul (listof attribute) (listof li))

struct
(struct dir html-full ()
#:extra-constructor-name make-dir)

A dir is (make-dir (listof attribute) (listof li))

struct
(struct menu html-full ()
#:extra-constructor-name make-menu)

A menu is (make-menu (listof attribute) (listof li))

struct
(struct dl html-full ()
#:extra-constructor-name make-dl)

A dl is (make-dl (listof attribute) (listof Contents-of-dl))

A Contents-of-dl is either

struct
(struct pre html-full ()
#:extra-constructor-name make-pre)

A pre is (make-pre (listof attribute) (listof Contents-of-pre))

A Contents-of-pre is either

struct
(struct object html-full ()
#:extra-constructor-name make-object)

An object is (make-object (listof attribute) (listof Contents-of-object-applet))

struct
(struct applet html-full ()
#:extra-constructor-name make-applet)

An applet is (make-applet (listof attribute) (listof Contents-of-object-applet))

A Contents-of-object-applet is either

param
G2

struct
(struct -map html-full ()
#:extra-constructor-name make--map)

A Map is (make--map (listof attribute) (listof Contents-of-map))

A Contents-of-map is either

area
fieldset
form
isindex
G10

struct
(struct a html-full ()
#:extra-constructor-name make-a)

An a is (make-a (listof attribute) (listof Contents-of-a))

A Contents-of-a is either

label
G7

struct
(struct address html-full ()
#:extra-constructor-name make-address)

An address is (make-address (listof attribute) (listof Contents-of-address))

A Contents-of-address is either

struct
(struct body html-full ()
#:extra-constructor-name make-body)

A body is (make-body (listof attribute) (listof Contents-of-body))

A Contents-of-body is either

A G12 is either

button
iframe
input
select
textarea

A G11 is either

a
label
G12

A G10 is either

address
blockquote
center
dir
div
dl
h1
h2
h3
h4
h5
h6
hr
menu
noframes
noscript
ol
p
pre
table
ul

A G9 is either

abbr
acronym
b
bdo
br
cite
code
dfn
em
i
kbd
-map
pcdata
q
s
samp
script
span
strike
strong
tt
u
var

A G8 is either

applet
basefont
big
font
img
object
small
sub
sup
G9

A G7 is either

A G6 is either

A G5 is either

label
G6

A G4 is either

A G3 is either

fieldset
isindex
G4
G11

A G2 is either

form
G3