NAME¶
ncgi - Procedures to manipulate CGI values.
SYNOPSIS¶
package require
Tcl 8.2
package require
ncgi ?1.3?
::ncgi::cookie cookie
::ncgi::decode str
::ncgi::empty name
::ncgi::exists name
::ncgi::encode string
::ncgi::header ?
type?
args
::ncgi::import cginame ?
tclname?
::ncgi::importAll args
::ncgi::importFile cmd cginame ?
filename?
::ncgi::input ?
fakeinput? ?
fakecookie?
::ncgi::multipart type query
::ncgi::nvlist
::ncgi::names
::ncgi::parse
::ncgi::parseMimeValue value
::ncgi::query
::ncgi::redirect url
::ncgi::reset query type
::ncgi::setCookie args
::ncgi::setDefaultValue key defvalue
::ncgi::setDefaultValueList key defvaluelist
::ncgi::setValue key value
::ncgi::setValueList key valuelist
::ncgi::type
::ncgi::urlStub ?
url?
::ncgi::value key ?
default?
::ncgi::valueList key ?
default?
DESCRIPTION¶
The
ncgi package provides commands that manipulate CGI values. These are
values that come from Web forms and are processed either by CGI scripts or web
pages with embedded Tcl code. Use the
ncgi package to query these
values, set and get cookies, and encode and decode www-url-encoded values.
In the simplest case, a CGI script first calls
::ncgi::parse and then
calls
::ncgi::value to get different form values. If a CGI value is
repeated, you should use
::ncgi::valueList to get back the complete
list of values.
An alternative to
::ncgi::parse is
::ncgi::input, which has
semantics similar to Don Libes'
cgi_input procedure.
::ncgi::input restricts repeated CGI values to have names that end with
"List". In this case,
::ncgi::value will return the complete
list of values, and
::ncgi::input will raise errors if it find repeated
form elements without the right name.
The
::ncgi::reset procedure can be used in test suites and Web servers to
initialize the source of the CGI values. Otherwise the values are read in from
the CGI environment.
The complete set of procedures is described below.
- ::ncgi::cookie cookie
- Return a list of values for cookie, if any. It is
possible that more than one cookie with the same name can be present, so
this procedure returns a list.
- ::ncgi::decode str
- Decode strings in www-url-encoding, which represents
special characters with a %xx sequence, where xx is the character code in
hex.
- ::ncgi::empty name
- Returns 1 if the CGI variable name is not present or
has the empty string as its value.
- ::ncgi::exists name
- The return value is a boolean. It returns 0 if the
CGI variable name is not present, and 1 otherwise.
- ::ncgi::encode string
- Encode string into www-url-encoded format.
- ::ncgi::header ?type? args
- Output the CGI header to standard output. This emits a
Content-Type: header and additional headers based on args, which is
a list of header names and header values. The type defaults to
"text/html".
- ::ncgi::import cginame ?tclname?
- This creates a variable in the current scope with the value
of the CGI variable cginame. The name of the variable is
tclname, or cginame if tclname is empty
(default).
- ::ncgi::importAll args
- This imports several CGI variables as Tcl variables. If
args is empty, then every CGI value is imported. Otherwise each CGI
variable listed in args is imported.
- ::ncgi::importFile cmd cginame
?filename?
- This provides information about an uploaded file from a
form input field of type file with name cginame. cmd
can be one of -server -client, -type or
-data.
- -client cginame
- returns the filename as sent by the client.
- -type cginame
- returns the mime type of the uploaded file.
- -data cginame
- returns the contents of the file.
- -server cginame filename
- writes the file contents to a local temporary file (or
filename if supplied) and returns the name of the file. The caller
is responsible for deleting this file after use.
- ::ncgi::input ?fakeinput?
?fakecookie?
- This reads and decodes the CGI values from the environment.
It restricts repeated form values to have a trailing "List" in
their name. The CGI values are obtained later with the
::ncgi::value procedure.
- ::ncgi::multipart type query
- This procedure parses a multipart/form-data query.
This is used by ::ncgi::nvlist and not normally called directly. It
returns an alternating list of names and structured values. Each structure
value is in turn a list of two elements. The first element is meta-data
from the multipart/form-data structure. The second element is the form
value. If you use ::ncgi::value you just get the form value. If you
use ::ncgi::valueList you get the structured value with meta data
and the value.
The type is the whole Content-Type, including the parameters like
boundary. This returns a list of names and values that describe the
multipart data. The values are a nested list structure that has some
descriptive information first, and the actual form value second. The
descriptive information is list of header names and values that describe
the content.
- ::ncgi::nvlist
- This returns all the query data as a name, value list. In
the case of multipart/form-data, the values are structured as described in
::ncgi::multipart.
- ::ncgi::names
- This returns all names found in the query data, as a list.
::ncgi::multipart.
- ::ncgi::parse
- This reads and decodes the CGI values from the environment.
The CGI values are obtained later with the ::ncgi::value procedure.
IF a CGI value is repeated, then you should use ::ncgi::valueList
to get the complete list of values.
- ::ncgi::parseMimeValue value
- This decodes the Content-Type and other MIME headers that
have the form of "primary value; param=val; p2=v2" It returns a
list, where the first element is the primary value, and the second element
is a list of parameter names and values.
- ::ncgi::query
- This returns the raw query data.
- ::ncgi::redirect url
- Generate a response that causes a 302 redirect by the Web
server. The url is the new URL that is the target of the redirect.
The URL will be qualified with the current server and current directory,
if necessary, to convert it into a full URL.
- ::ncgi::reset query type
- Set the query data and Content-Type for the current CGI
session. This is used by the test suite and by Web servers to initialize
the ncgi module so it does not try to read standard input or use
environment variables to get its data. If neither query or
type are specified, then the ncgi module will look in the
standard CGI environment for its data.
- ::ncgi::setCookie args
- Set a cookie value that will be returned as part of the
reply. This must be done before ::ncgi::header or
::ncgi::redirect is called in order for the cookie to be returned
properly. The args are a set of flags and values:
- -name name
- -value value
- -expires date
- -path path restriction
- -domain domain restriction
- ::ncgi::setDefaultValue key defvalue
- Set a CGI value if it does not already exists. This affects
future calls to ::ncgi::value (but not future calls to
::ncgi::nvlist). If the CGI value already is present, then this
procedure has no side effects.
- ::ncgi::setDefaultValueList key
defvaluelist
- Like ::ncgi::setDefaultValue except that the value
already has list structure to represent multiple checkboxes or a
multi-selection.
- ::ncgi::setValue key value
- Set a CGI value, overriding whatever was present in the CGI
environment already. This affects future calls to ::ncgi::value
(but not future calls to ::ncgi::nvlist).
- ::ncgi::setValueList key valuelist
- Like ::ncgi::setValue except that the value already
has list structure to represent multiple checkboxes or a
multi-selection.
- ::ncgi::type
- Returns the Content-Type of the current CGI values.
- ::ncgi::urlStub ?url?
- Returns the current URL, but without the protocol, server,
and port. If url is specified, then it defines the URL for the
current session. That value will be returned by future calls to
::ncgi::urlStub
- ::ncgi::value key ?default?
- Return the CGI value identified by key. If the CGI
value is not present, then the default value is returned instead.
This value defaults to the empty string.
If the form value key is repeated, then there are two cases: if
::ncgi::parse was called, then ::ncgi::value only returns
the first value associated with key. If ::ncgi::input was
called, then ::ncgi::value returns a Tcl list value and key
must end in "List" (e.g., "skuList"). In the case of
multipart/form-data, this procedure just returns the value of the form
element. If you want the meta-data associated with each form value, then
use ::ncgi::valueList.
- ::ncgi::valueList key ?default?
- Like ::ncgi::value, but this always returns a list
of values (even if there is only one value). In the case of
multipart/form-data, this procedure returns a list of two elements. The
first element is meta-data in the form of a parameter, value list. The
second element is the form value.
EXAMPLES¶
Uploading a file
HTML:
<html>
<form action="/cgi-bin/upload.cgi" method="POST" enctype="multipart/form-data">
Path: <input type="file" name="filedata"><br>
Name: <input type="text" name="filedesc"><br>
<input type="submit">
</form>
</html>
TCL: upload.cgi
#!/usr/local/bin/tclsh
::ncgi::parse
set filedata [::ncgi::value filedata]
set filedesc [::ncgi::value filedesc]
puts "<html> File uploaded at <a href=\"/images/$filedesc\">$filedesc</a> </html>"
set filename /www/images/$filedesc
set fh [open $filename w]
puts -nonewline $fh $filedata
close $fh
BUGS, IDEAS, FEEDBACK¶
This document, and the package it describes, will undoubtedly contain bugs and
other problems. Please report such in the category
ncgi of the
Tcllib SF Trackers [
http://sourceforge.net/tracker/?group_id=12883].
Please also report any ideas for enhancements you may have for either package
and/or documentation.
SEE ALSO¶
html
KEYWORDS¶
CGI, cookie, form, html
CATEGORY¶
CGI programming