19 Cookie: HTTP Client Storage

(require net/cookie)

The net/cookie library provides utilities for using cookies as specified in RFC 2109 [RFC2109].

19.1 Functions

(cookie? v) → boolean?

v : any/c

Returns #t if v represents a cookie, #f otherwise.

(set-cookie name value) → cookie?

name : string?

value : string?

Creates a new cookie, with default values for required fields.

(cookie:add-comment cookie comment) → cookie?

cookie : cookie?

comment : string?

Modifies cookie with a comment, and also returns cookie.

(cookie:add-domain cookie domain) → cookie?

cookie : cookie?

domain : string?

Modifies cookie with a domain, and also returns cookie. The domain must match a prefix of the request URI.

(cookie:add-max-age cookie seconds) → cookie?

cookie : cookie?

seconds : exact-nonnegative-integer?

Modifies cookie with a maximum age, and also returns cookie. The seconds argument is number of seconds that a client should retain the cookie.

(cookie:add-path cookie path) → cookie?

cookie : cookie?

path : string?

Modifies cookie with a path, and also returns cookie.

(cookie:secure cookie secure) → cookie?

cookie : cookie?

secure : boolean?

Modifies cookie with a security flag, and also returns cookie.

(cookie:version cookie version) → cookie?

cookie : cookie?

version : exact-nonnegative-integer?

Modifies cookie with a version, and also returns cookie. The default is the only known incarnation of HTTP cookies: 1.

(print-cookie cookie) → string?

cookie : cookie?

Prints cookie to a string. Empty fields do not appear in the output except when there is a required default.

(get-cookie name cookies) → (listof string?)

name : string?

cookies : string?

Returns a list with all the values (strings) associated with name.

The method used to obtain the "Cookie" header depends on the web server. It may be an environment variable (CGI), or you may have to read it from the input port (FastCGI), or maybe it comes in an initial-request structure, etc. The get-cookie and get-cookie/single procedure can be used to extract fields from a "Cookie" field value.

(get-cookie/single name cookies) → (or/c string? false/c)

name : string?

cookies : string?

Like get-cookie, but returns the just first value string associated to name, or #f if no association is found.

(struct   (cookie-error exn:fail)   ())

Raised for errors when handling cookies.

19.2 Examples

19.2.1 Creating a cookie

(let ((c (cookie:add-max-age

(cookie:add-path

(set-cookie "foo" "bar")

"/servlets")

3600)))

(print-cookie c))

Produces

  "foo=bar; Max-Age=3600; Path=/servlets; Version=1"

To use this output in a “regular” CGI, instead of the last line use:

  (display (format "Set-Cookie: ~a" (print-cookie c)))

and to use with the PLT Web Server, use:

(make-response/full code message (current-seconds) mime

`((Set-Cookie . ,(print-cookie c)))

body)

19.2.2 Parsing a cookie

Imagine your Cookie header looks like this:

> (define cookies       "test2=2; test3=3; xfcTheme=theme6; xfcTheme=theme2")

Then, to get the values of the xfcTheme cookie, use

> (get-cookie "xfcTheme" cookies)

("theme6" "theme2")

> (get-cookie/single "xfcTheme" cookies)

"theme6"

If you try to get a cookie that simply is not there:

> (get-cookie/single "foo" cookies)

#f

> (get-cookie "foo" cookies)

()

Note that not having a cookie is normally not an error. Most clients won’t have a cookie set then first arrive at your site.

19.3 Cookie Unit

(require net/cookie-unit)

cookie@ : unit?

Imports nothing, exports cookie^.

19.4 Cookie Signature

(require net/cookie-sig)

cookie^ : signature

Includes everything exported by the net/cookie module.