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Wapp - A Web-Application Framework for TCL
========================================
1.0 Introduction
----------------
Wapp is a simple and lightweight framework that strives to simplify the
construction of web application written in TCL. The same Wapp application
can be launched in multiple ways:
* From the command-line (ex: <tt>tclsh app.tcl</tt>). In this mode,
The wapp-app find an available TCL port on localhost, starts an
in-process web server listening on that port, and then launches the
users default web browser directed at localhost:$port
* As a CGI program
* As an SCGI program
* As a stand-alone web server
All four methods of launching the application provide the same interface
to the user.
1.0 Hello World!
----------------
Wapp is designed to be easy to use. A hello-world program is as follows:
>
package require wapp
proc wapp-default {req} {
wapp "<h1>Hello, World!</h1>\n"
}
wapp-start $::argv
The application defines one or more procedures that accept HTTP requests.
For an HTTP request where the initial portion of the URI is "abcde", the
procedure named "wapp-page-abcde" will be invoked to construct the reply.
If no such procedure exists, "wapp-default" is invoked instead.
The procedure generates a reply using one or more calls to the "wapp"
command. Each "wapp" command appends new text to the reply.
The "wapp-start" command starts up the built-in web server.
To run this application, but the code above into a file named "main.tcl"
and then run type "<tt>tclsh main.tcl</tt>" at the command-line. That
should cause the "Hello, World!" page to appear in your web browser.
### 1.1 A Slightly Longer Example
Information about each HTTP request is encoded in the global ::wapp
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Wapp - A Web-Application Framework for TCL
========================================
1.0 Introduction
----------------
Wapp is a lightweight framework that strives to simplify the
construction of web application written in TCL. The same Wapp application
can be launched in multiple ways:
* From the command-line (ex: "<tt>tclsh app.tcl</tt>"). In this mode,
The wapp finds an available TCL port on localhost, starts an
in-process web server listening on that port, and then launches the
users default web browser directed at localhost:$port
* As a CGI program
* As an SCGI program
* As a stand-alone web server
All four methods use the same application code and present the same
interface to the application user.
1.0 Hello World!
----------------
Wapp is designed to be easy to use. A hello-world program is as follows:
>
package require wapp
proc wapp-default {req} {
wapp "<h1>Hello, World!</h1>\n"
}
wapp-start $::argv
The application defines one or more procedures that accept HTTP requests
and generate appropriate replies.
For an HTTP request where the initial portion of the URI is "abcde", the
procedure named "wapp-page-abcde" will be invoked to construct the reply.
If no such procedure exists, "wapp-default" is invoked instead.
The procedure generates a reply using one or more calls to the "wapp"
command. Each "wapp" command appends new text to the reply.
The "wapp-start" command starts up the built-in web server.
To run this application, copy the code above into a file named "main.tcl"
and then run type "<tt>tclsh main.tcl</tt>" at the command-line. That
should cause the "Hello, World!" page to appear in your web browser.
### 1.1 A Slightly Longer Example
Information about each HTTP request is encoded in the global ::wapp
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the same as "wapp" (it appends its argument text to the web page under
construction) except that the argument to "wapp-unsafe" is allowed to contain
TCL variable and command expansions. The "wapp" command will generate a
warning if its argument contains TCL variable or command expansions, as a
defense against accidental XSS vulnerabilities.
The /env page is implemented by the "wapp-page-env" proc. This proc
generates an HTML unordered list where each element of the list describes
a single value in the global ::wapp dict. The "wapp-escape-html"
[http://localhost:8080/env/longer/path?q1=5&title=hello+world%21]
+ **HTTP_HOST**
The hostname (or IP address) and port that the client used to create
the current HTTP request. This is the first part of the request URL.
+ **HTTP_USER_AGENT**
The name of the web-browser or other client program that generated
the current HTTP request.
+ **HTTPS**
If the HTTP request arrived of SSL, then this variable has the value "on".
For an unencrypted request, the variable does not exist.
+ **REMOTE_ADDR**
The IP address and port from which the HTTP request originated.
+ **SCRIPT_NAME**
In CGI mode, this is the name of the CGI script in the URL. In other
words, it is the initial part of the URL path that identifies the
CGI script. For other modes, this variable is an empty string.
+ **PATH_INFO**
The part of the URL path that follows the SCRIPT_NAME. For all modes
other than CGI, this is exactly the URL pathname.
+ **REQUEST_URI**
The URL for the inbound request, without the initial "http://" or
"https://" and without the HTTP_HOST.
+ **REQUEST_METHOD**
"GET" or "HEAD" or "POST"
+ **BASE_URL**
The text of the request URL through the SCRIPT_NAME. This value can
be prepended to hyperlinks to ensure that the correct page is reached by
those hyperlinks.
+ **PATH_HEAD**
The first element in the PATH_INFO. The value of PATH_HEAD is used to
select one of the "wapp-page-XXXXX" commands to run in order to generate
the output web page.
+ **PATH_TAIL**
All of PATH_INFO that follows PATH_HEAD.
+ **SELF_URL**
The URL for the current page, stripped of query parameter. This is
useful for filling in the action= attribute of forms.
### 1.3 Additional Wapp Commands
The following utility commands are available for use by applications built
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the same as "wapp" (it appends its argument text to the web page under
construction) except that the argument to "wapp-unsafe" is allowed to contain
TCL variable and command expansions. The "wapp" command will generate a
warning if its argument contains TCL variable or command expansions, as a
defense against accidental XSS vulnerabilities.
The /env page is implemented by the "wapp-page-env" proc. This proc
generates an HTML that describes the content of the ::wapp dict.
Keys that begin with "." are for internal use by Wapp and are skipped
for this display. The "wapp-escape-html"
command is like "wapp" and "wapp-unsafe" except that "wapp-escape-html"
escapes HTML markup so that it displays correctly in the output.
### 1.2 The ::wapp Global Dict
To better understand how the ::wapp dict works, try running the previous
sample program, but extend the /env URL with extra path elements and query
parameters. For example:
<http://localhost:8080/env/longer/path?q1=5&title=hello+world%21>
Notice how the query parameters in the input URL are decoded and become
elements of the ::wapp dict. The same thing occurs with POST parameters
and cookies - they are all converted into entries in the ::wapp dict
variable so that the parameters are easily accessible to page generation
procedures.
The ::wapp variable contains additional information about the request,
roughly corresponding to CGI environment variables. To prevent environment
information from overlapping and overwriting query parameters, all the
environment information uses upper-case names and all query parameters
are required to be lower case. If an input URL contains an upper-case
query parameter (or POST parameter or cookie), that parameter is silently
omitted from the ::wapp variable
The ::wapp variable contains the following environment values:
+ **HTTP\_HOST**
The hostname (or IP address) and port that the client used to create
the current HTTP request. This is the first part of the request URL.
+ **HTTP\_USER\_AGENT**
The name of the web-browser or other client program that generated
the current HTTP request.
+ **HTTPS**
If the HTTP request arrived of SSL, then this variable has the value "on".
For an unencrypted request, the variable does not exist.
+ **REMOTE\_ADDR**
The IP address and port from which the HTTP request originated.
+ **SCRIPT_NAME**
In CGI mode, this is the name of the CGI script in the URL. In other
words, it is the initial part of the URL path that identifies the
CGI script. For other modes, this variable is an empty string.
+ **PATH\_INFO**
The part of the URL path that follows the SCRIPT\_NAME. For all modes
other than CGI, this is exactly the URL pathname.
+ **REQUEST\_URI**
The URL for the inbound request, without the initial "http://" or
"https://" and without the HTTP\_HOST.
+ **REQUEST\_METHOD**
"GET" or "HEAD" or "POST"
+ **BASE\_URL**
The text of the request URL through the SCRIPT\_NAME. This value can
be prepended to hyperlinks to ensure that the correct page is reached by
those hyperlinks.
+ **PATH\_HEAD**
The first element in the PATH\_INFO. The value of PATH\_HEAD is used to
select one of the "wapp-page-XXXXX" commands to run in order to generate
the output web page.
+ **PATH\_TAIL**
All of PATH\_INFO that follows PATH\_HEAD.
+ **SELF\_URL**
The URL for the current page, stripped of query parameter. This is
useful for filling in the action= attribute of forms.
### 1.3 Additional Wapp Commands
The following utility commands are available for use by applications built
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