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CGI: URL Encoding: Difference between revisions
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(Created page with "{{Nav CGI}} '''URL Encoding''' Dynamic pages are not all about flashing images and changing content it also includes user interaction. More specifically user data sent to your w...") |
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'''URL Encoding''' | '''URL Encoding''' | ||
Dynamic pages are not all about flashing images and changing content | Dynamic pages are not all about flashing images and changing content. They also can include user interaction, such as user data sent to your web page for processing. Data is sent in a special format referred to as URL encoding. This page provides an overview of URL encoding and how to extract data sent to the server. | ||
__TOC__ | __TOC__ | ||
==Encoding== | ==Encoding== | ||
Data arrives with a page request tagged with either GET or POST markers; it may have been initiated by a user | Data arrives with a page request tagged with either GET or POST markers; it may have been initiated by a user filling in a form or by a crafted link from a previous request. The data is a string of ASCII characters included with the URL; certain characters have a special meaning and are encoded before being sent. | ||
===Table of common special characters=== | ===Table of common special characters=== | ||
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===Browser encoding=== | ===Browser encoding=== | ||
A browser automatically encodes data from a form | A browser automatically encodes data from a form, but data included with links must be pre-coded. | ||
{| | {| | ||
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Scripting languages provide URL Encoding and Decoding functions. | Scripting languages provide URL Encoding and Decoding functions. | ||
The table on the right lists three script languages and their functions: | |||
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{|cellpadding="4" cellspacing="1" style="background:#000000;" | {|cellpadding="4" cellspacing="1" style="background:#000000;" | ||
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|} | |} | ||
|} | |} | ||
==Environment variables== | ==Environment variables== | ||
When Apache runs a CGI script it passes its current set of environment variables to the script. Included in these are the data sent and method (GET or POST) used for sending this data. Using these environment variables name-value pairs can be extracted. | When Apache runs a CGI script it passes its current set of environment variables to the script. Included in these are the data sent and method (GET or POST) used for sending this data. Using these environment variables, name-value pairs can be extracted. | ||
===Test Script 6 - Display environment variables=== | ===Test Script 6 - Display environment variables=== | ||
{| | {| | ||
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The script produces output as shown on right. | The script produces output as shown on right. | ||
Your data displayed will differ what is of interest are the variable names passed to a script. Of particular importance are the variables REQUEST_METHOD and QUERY_STRING | Your data displayed will differ but what is of interest are the variable names passed to a script. Of particular importance are the variables REQUEST_METHOD and QUERY_STRING. These allow data sent with the page request to be extracted. | ||
Remember a query string is appended to a URL and sets the method to GET. This information is available via the environment variables. | Remember that a query string is appended to a URL and sets the method to GET. This information is available via the environment variables. | ||
POST data can be relatively long and exceed the allowed environment variable length. Because of this it is treated differently and not accessible via an environment variable. Instead it is sent directly to the standard input stream | POST data can be relatively long and exceed the allowed environment variable length. Because of this it is treated differently and is not accessible via an environment variable. Instead it is sent directly to the standard input stream, allowing it to be captured in a user defined variable. | ||
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<pre> | <pre> | ||
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</pre> | </pre> | ||
'''Note:''' The default method is GET attempting to read | '''Note:''' The default method is GET; attempting to read POST data when the method is set to GET results in the following error: "Input past end of file" Therefore, before reading POST data, always check that the method is set to POST. | ||
==Test Script 7 - Raw data form example== | ==Test Script 7 - Raw data form example== | ||
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'''Raw data test script:''' | '''Raw data test script:''' | ||
This script contains two forms | This script contains two forms. These send data either using GET or POST. It displays the method used and data sent. Data is displayed raw, meaning that it is not decoded or separated into variables. | ||
* Create a new file '''test7.vbs''' with content as shown on right. | * Create a new file '''test7.vbs''' with content as shown on right. | ||
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English | English | ||
</pre> | </pre> | ||
This gives encoded string as shown below: | This gives the encoded string as shown below: | ||
<pre> | <pre> | ||
text=Cat++%26+dog%3D50a%25&Language=English | text=Cat++%26+dog%3D50a%25&Language=English | ||
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</pre> | </pre> | ||
|} | |} | ||
==Data organisation== | ==Data organisation== | ||
Data is organised as '''variable''' special character "=" '''value''' pairs | Data is organised as '''variable''' special character "=" '''value''' pairs. These pairs are concatenated using the special character '''&'''. Any special characters appearing in the value string are encoded. It’s an elegant structure making it easy to extract variables and their associated data. | ||
* Using the above string as an example: text=Cat++%26+dog%3D50a%25&Language=English | * Using the above string as an example: text=Cat++%26+dog%3D50a%25&Language=English | ||
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** array_data[Language] = "English | ** array_data[Language] = "English | ||
===Test Script 8 - Function Get CGI variables=== | ===Test Script 8 - Function Get CGI variables=== | ||
{| | {| | ||
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'''Get CGI variables test script:''' | '''Get CGI variables test script:''' | ||
This script contains two forms | This script contains two forms. These send data either using GET or POST. It uses a function to separate variables sent and decodes their corresponding values which are then displayed. | ||
* Create a new file '''test8.vbs''' with content as shown on right. | * Create a new file '''test8.vbs''' with content as shown on right. | ||
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* Enter: <nowiki>http://localhost:8081/vbs_test/test8.vbs</nowiki> into browser. | * Enter: <nowiki>http://localhost:8081/vbs_test/test8.vbs</nowiki> into browser. | ||
Click either the Get or Post buttons encoded and decoded data | Click either the Get or Post buttons; encoded and decoded data are displayed. | ||
'''Note''' After testing the encoded data display section can be removed from the function. | '''Note:''' After testing the encoded data display, this section can be removed from the function. | ||
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*This array is scanned using a '''for''' loop. Each variable-value pair is split using '''split(variable_array(i), "=")''' | *This array is scanned using a '''for''' loop. Each variable-value pair is split using '''split(variable_array(i), "=")''' | ||
*The '''cgi_variable(0)''' part is used | *The '''cgi_variable(0)''' part is used directly for the index while '''cgi_variable(1)''' requires further processing. | ||
*First the special character "+" is replaced with a space and the result decoded. | *First the special character "+" is replaced with a space and the result decoded. | ||
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*The index '''cgi_variable(0)''' and value '''decoded_value''' are added to the dictionary. | *The index '''cgi_variable(0)''' and value '''decoded_value''' are added to the dictionary. | ||
*Finally the function returns the dictionary | *Finally, the function returns the dictionary. | ||
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<pre> | <pre> | ||
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|} | |} | ||
== Summary == | == Summary == | ||
URL encoding and decoding is a very important part of creating dynamic web sites. Although the above is not a definitive guide it provides enough detail to get you up and running. | URL encoding and decoding is a very important part of creating dynamic web sites. Although the above is not a definitive guide, it provides enough detail to get you up and running. | ||
Of particular importance is the Get CGI variables function | Of particular importance is the Get CGI variables function. You can use this as is, alternatively roll your own or use a third party version. A better solution is to use a class. This is covered on the [[CGI: VBScript CGI Property Class 1|VBScript CGI Property Class]] page | ||
At this stage you currently have enough information to creative dynamic web pages written in VBScript! Test script eight is a working example of a dynamic web page. Perhaps you would prefer writing your script in JavaScript (JScript) this is covered next. | At this stage you currently have enough information to creative dynamic web pages written in VBScript! Test script eight is a working example of a dynamic web page. Perhaps you would prefer writing your script in JavaScript (JScript) this is covered next. | ||
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==Where to next== | ==Where to next== | ||
[[CGI: JavaScript CGI| | The [[CGI: JavaScript CGI|next page]] covers JavaScript (JScript) CGI. | ||
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[[Category: Tutorials]] | [[Category: Tutorials]] | ||
[[Category: How To]] | [[Category: How To]] | ||
[[Category: Mini Servers]] | [[Category: Mini Servers]] | ||