Next: cookies, Previous: filesystem, Up: Top
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 value
- Encapsulate 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-list
- Return a list of strings suitable for passing to
environ
or as the second argument toexecle
.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 read-first-line
from the parse-request module.
(define PORT ...) (define UPATH (list-ref (read-first-line PORT) 1)) (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.