|
Prev Up Next
Here is an example Scheme CGI script,
testcgi.scm, that outputs the settings of some
commonly used CGI environment variables. This
information is returned as a new, freshly created, page
to the browser. The returned page is simply whatever
the CGI script writes to its standard output. This is
how CGI scripts talk back to whoever called them -- by
giving them a new page.
Note that the script first outputs the line
content-type: text/plain
followed by a blank line. This is standard ritual
for a web server serving up a page. These two lines
aren't part of what is actually displayed as the page.
They are there to inform the browser that the page being sent
is plain (ie, un-marked-up) text, so the browser can
display it appropriately. If we were producing text
marked up in HTML, the
content-type would be
text/html.
The script testcgi.scm:
#!/bin/sh
":";exec /usr/local/bin/mzscheme -r $0 "$@"
;Identify content-type as plain text.
(display "content-type: text/plain") (newline)
(newline)
;Generate a page with the requested info. This is
;done by simply writing to standard output.
(for-each
(lambda (env-var)
(display env-var)
(display " = ")
(display (or (getenv env-var) ""))
(newline))
'("AUTH_TYPE"
"CONTENT_LENGTH"
"CONTENT_TYPE"
"DOCUMENT_ROOT"
"GATEWAY_INTERFACE"
"HTTP_ACCEPT"
"HTTP_REFERER" ; sic
"HTTP_USER_AGENT"
"PATH_INFO"
"PATH_TRANSLATED"
"QUERY_STRING"
"REMOTE_ADDR"
"REMOTE_HOST"
"REMOTE_IDENT"
"REMOTE_USER"
"REQUEST_METHOD"
"SCRIPT_NAME"
"SERVER_NAME"
"SERVER_PORT"
"SERVER_PROTOCOL"
"SERVER_SOFTWARE"))
testcgi.scm can be called directly by opening it on
a browser. The URL is:
http://www.foo.org/cgi-bin/testcgi.scm
Alternately, testcgi.scm can occur as a link in an
HTML file, which you can click. Eg,
... To view some common CGI environment variables, click
<a href="http://www.foo.org/cgi-bin/testcgi.scm">here</a>.
...
However testcgi.scm is launched, it will produce a
plain text page containing the settings of the
environment variables. An example output:
AUTH_TYPE =
CONTENT_LENGTH =
CONTENT_TYPE =
DOCUMENT_ROOT = /home/httpd/html
GATEWAY_INTERFACE = CGI/1.1
HTTP_ACCEPT = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*
HTTP_REFERER =
HTTP_USER_AGENT = Mozilla/3.01Gold (X11; I; Linux 2.0.32 i586)
PATH_INFO =
PATH_TRANSLATED =
QUERY_STRING =
REMOTE_HOST = 127.0.0.1
REMOTE_ADDR = 127.0.0.1
REMOTE_IDENT =
REMOTE_USER =
REQUEST_METHOD = GET
SCRIPT_NAME = /cgi-bin/testcgi.scm
SERVER_NAME = localhost.localdomain
SERVER_PORT = 80
SERVER_PROTOCOL = HTTP/1.0
SERVER_SOFTWARE = Apache/1.2.4
Prev Up Next | 
