ncgi(3)

ncgi(3tcl) CGI Support ncgi(3tcl)

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NAME
ncgi - Procedures to manipulate CGI values.

SYNOPSIS
package require Tcl 8.4

package require ncgi ?1.4.4?

::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?

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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 re-
peated CGI values to have names that end with "List". In this case,
::ncgi::value will return the complete list of values, and ::ncgi::in-
put 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 in-
put 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 struc-
ture 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 de-
scribe the multipart data. The values are a nested list struc-
ture 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 de-
scribed 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::val-
ueList 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 el-
ement 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 redi-
rect. 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 fu-
ture 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-se-
lection.

::ncgi::setValue key value
Set a CGI value, overriding whatever was present in the CGI en-
vironment 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 cur-
rent 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 multi-
part/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 Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
also report any ideas for enhancements you may have for either package
and/or documentation.

When proposing code changes, please provide unified diffs, i.e the out-
put of diff -u.

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