1 Updated: July 3, 2012 (http://curl.haxx.se/docs/http-cookies.html)
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13 1.2 Cookies saved to disk
14 1.3 Cookies with curl the command line tool
15 1.4 Cookies with libcurl
16 1.5 Cookies with javascript
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24 HTTP cookies are pieces of 'name=contents' snippets that a server tells the
25 client to hold and then the client sends back those the server on subsequent
26 requests to the same domains/paths for which the cookies were set.
28 Cookies are either "session cookies" which typically are forgotten when the
29 session is over which is often translated to equal when browser quits, or
30 the cookies aren't session cookies they have expiration dates after which
31 the client will throw them away.
33 Cookies are set to the client with the Set-Cookie: header and are sent to
34 servers with the Cookie: header.
36 For a very long time, the only spec explaining how to use cookies was the
37 original Netscape spec from 1994: http://curl.haxx.se/rfc/cookie_spec.html
39 In 2011, RFC6265 (http://www.ietf.org/rfc/rfc6265.txt) was finally published
40 and details how cookies work within HTTP.
42 1.2 Cookies saved to disk
44 Netscape once created a file format for storing cookies on disk so that they
45 would survive browser restarts. curl adopted that file format to allow
46 sharing the cookies with browsers, only to see browsers move away from that
47 format. Modern browsers no longer use it, while curl still does.
49 The netscape cookie file format stores one cookie per physical line in the
50 file with a bunch of associated meta data, each field separated with
51 TAB. That file is called the cookiejar in curl terminology.
53 When libcurl saves a cookiejar, it creates a file header of its own in which
54 there is a URL mention that will link to the web version of this document.
56 1.3 Cookies with curl the command line tool
58 curl has a full cookie "engine" built in. If you just activate it, you can
59 have curl receive and send cookies exactly as mandated in the specs.
65 tell curl a file to read cookies from and start the cookie engine, or if
66 it isn't a file it will pass on the given string. -b name=var works and so
69 -j, --junk-session-cookies
71 when used in combination with -b, it will skip all "session cookies" on
72 load so as to appear to start a new cookie session.
76 tell curl to start the cookie engine and write cookies to the given file
79 1.4 Cookies with libcurl
81 libcurl offers several ways to enable and interface the cookie engine. These
82 options are the ones provided by the native API. libcurl bindings may offer
83 access to them using other means.
87 Is used when you want to specify the exact contents of a cookie header to
92 Tell libcurl to activate the cookie engine, and to read the initial set of
93 cookies from the given file. Read-only.
97 Tell libcurl to activate the cookie engine, and when the easy handle is
98 closed save all known cookies to the given cookiejar file. Write-only.
102 Provide detailed information about a single cookie to add to the internal
103 storage of cookies. Pass in the cookie as a HTTP header with all the
104 details set, or pass in a line from a netscape cookie file. This option
105 can also be used to flush the cookies etc.
109 Extract cookie information from the internal cookie storage as a linked
112 1.5 Cookies with javascript
114 These days a lot of the web is built up by javascript. The webbrowser loads
115 complete programs that render the page you see. These javascript programs
116 can also set and access cookies.
118 Since curl and libcurl are plain HTTP clients without any knowledge of or
119 capability to handle javascript, such cookies will not be detected or used.
121 Often, if you want to mimic what a browser does on such web sites, you can
122 record web browser HTTP traffic when using such a site and then repeat the
123 cookie operations using curl or libcurl.