urlcp settings control what headers are sent
with requests, which can affect what document the remote web
server will return:
accept(2 arguments) Set the HTTP
Acceptheader list of acceptable/desired MIME types. Each value of the first argument (
$value1) is a MIME media range, e.g. "
text/html" or "
image/*". The corresponding value of
$value2, if given, is a "quality" value, a percentage number from 0-100. If greater than 0, the
qvalue of the corresponding media range is set to that value. If
$value2has fewer values than
$value1, the last value of
$value2, if any, is reused. See the HTTP specification for details on how these values are used by Web servers. The default
Acceptlist (if not set) is "
*/*", e.g. any type.
Accept list may affect the content type of
the document a Web server will send for a given URL, but it is no
guarantee that the requested type(s) will be returned. It is up
to the server to send the most appropriate form of a document
based on the
clearheaders(no arguments) Clear any headers set with
header(list, 2 arguments)
Set the HTTP request headers given in the first argument, to the
corresponding values in the second argument. This can be used to
set additional headers not otherwise settable. Note that cookies
are automatically handled in version 4.01.1022000000 20020521 and
later and thus
Cookie headers do not generally need to be
set in those versions.
In version 5.01.1245974000 20090625 and later, headers specified
with this setting will replace builtin headers of the same name
Host etc.), instead of causing a second copy of the
header to be sent. Note that setting/overriding builtin headers
can cause erratic behavior, as user-specified values may interfere
with library functionality. Builtin headers include
User-Agent. All of these are set
automatically by the library and/or have other
settings that are the preferred method of controlling them.
Setting an empty value for a header will clear it (prevent it from being sent). It is not possible to send the same header two or more times: later values will merely replace earlier ones and the header will be sent at most once. To send multiple values for a header, set a single value with multiple tokens according to the HTTP syntax for the given header (typically comma-separated).
ifmodsince(string) Sets the HTTP
If-Modified-Sinceheader to the given value. The argument is a time, either in Texis-parseable format or HTTP date format (
www, dd mmm yyyy hh:mm:ss GMT). If the argument is empty, the header is cancelled.
If-Modified-Since header creates a
conditional request: the document is only returned if it has been
changed since the given time, otherwise an empty document is
returned. Setting this header on a per-page basis, to the
Last-Modified value from the previous fetch, can reduce the
traffic when re-walking a site: only new documents are returned.
Note that it is up to the remote server to handle the
If-Modified-Since header, and the given time is interpreted
in its domain.
useragent(string) Sets the
User-Agentheader sent with HTTP requests. The default is a Netscape-compatible string.