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Often the server cannot do everything by itself, and makes use of external programs invoked in a common gateway interface environment. These programs are also known as CGI scripts.
The (www server-utils cgi-prep) module provide a procedure to set up
such an environment. Actually invoking the CGI script is not covered.
Return a closure encapsulating initial-bindings, a list of
pairs (name . value), where name is a symbol
listed in the following table, and value is a string unless
otherwise noted.
server-hostname
gateway-interface
server-port (integer)
request-method
path-info
path-translated
script-name
query-string
remote-host
remote-addr
authentication-type
remote-user
remote-ident
content-type
content-length (integer, or #f)
http-user-agent
http-cookie
server-software
server-protocol
http-accept-types (list of strings)
If name is not recognized, signal "unrecognized key" error.
Encapsulation includes name=value formatting.
The closure accepts these commands:
name valueEncapsulate an additional binding. name and value are as above.
#:clear!Drop the additional bindings. Note that initial bindings can never be dropped (you can always create a new closure).
#:environ-listReturn a list of strings suitable for passing to environ
or as the second argument to execle.
Any other command results in a "bad command" error.
Following is a simple example of how to use cgi-environment-manager.
A more realistic example would include port and connection management,
input validation, error handling, logging, etc. First, we set up the
manager with more-or-less constant bindings.
(define M (cgi-environment-manager
'((server-software . "FooServe/24")
(server-protocol . "HTTP/1.0")
(server-port . 80))))
Later, we add connection-specific bindings. We use receive-request
from the (www server-utils parse-request) module.
(define PORT ...) (define REQUEST (receive-request PORT)) (define UPATH (request-upath REQUEST)) (define QMARK (string-index UPATH #\?)) (define CGI (substring UPATH 0 QMARK)) (M 'script-name CGI) (M 'query-string (substring UPATH (1+ QMARK)))
Lastly, we spawn the child process, passing the constructed environment as
the second arg to execle, and drop the connection-specific bindings
afterwards.
(let ((pid (primitive-fork)))
(if (zero? pid)
(execle CGI (M #:environ-list) (list CGI)) ; child
(waitpid pid))) ; parent
(M #:clear!)
Now we can re-use M for another connection.
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