iTP Secure WebServer System Administrator's Guide (Version 7.0)

Using Common Gateway Interface (CGI) Programs
iTP Secure WebServer System Administrator’s Guide—523346-012
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HTTP Header Variables
If more than one client header has the same name, the server creates a single
environment variable based on the common name (CN). For example, the variable for
multiple Accept: headers would be HTTP_ACCEPT. The single value assigned to this
variable would consist of the Web client headers separated by commas. For example,
if the multiple client headers are:
Accept: image/gif
Accept: image/jpeg
the server would assign the value:
image/gif, image/jpeg
to environment variable HTTP_ACCEPT.
The server might omit environment variables for headers it has already processed,
such as Authorization:, Content-length:, and Content-type:.
Table 8-4 lists some commonly used HTTP header environment variables.
Table 8-4. Sample HTTP Header Variables (page 1 of 2)
Sample HTTP Variable Description
HTTP_ACCEPT This variable lists the MIME headers that the Web client is
able to accept.
Format:
[ type/subtype, ] [ type/subtype, ] …
Example:
image/gif, image/jpeg
HTTP_ACCEPT_CHARSET This variable lists the character sets that the Web client is
able to accept.
Format:
[ char-set-name, ] [ char-set-name, ] …
Example:
iso-8859-5, Shift_JIS
HTTP_ACCEPT_LANGUAGE This variable lists the set of languages that the Web client
prefers as a response.
Format:
[ language, ] [ language, ] …
Example:
da, en-gb
HTTP_HOST This variable lists the IP host and port of the resource
being requested. port is required only if the value is other
than 80.
Format:
host-name[:port ]
Example:
www.w3.org:10300