User:Emily/Prototyping/Trimester 03/03: Difference between revisions

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CGI Basics
: understanding--> set up the HTTP server so that whatever a file in a certain directory is requested that file is not sent back instead it is executed as a program, and whatever that program outputs is sent back for your browser to display("Content-Type: text/html").
:CGI programs can be python script, shell script, perl, c or c++ program ...
:Get Method
::url-->
<source lang=python>
"content-type: text/html\r\n\r\n"
print "<h2> Hello %s %s</h2>" % (first_name, last_name)
</source>
::form-->
<source lang=python>
<form action="..." method="get">
<input type="text" name="..." />
<input type="submit" value="submit" />
</form>
</source>
:Post Method (send information as separate message instead of a text string)
::form-->
<source lang=python>
<form action="..." method="post">... </form>
</source>
::checkbox-->
<source lang=python>
<form action="..." method="post" target="_blank">
<input type="checkbox" name="..." value="on"/>
<input type="submit" value="submit" />
</form>
</source>
::radio button-->
<source lang=python>
<form action="..." method="post" target="_blank">
<input type="radio" name="..." value="on"/>
<input type="submit" value="submit" />
</form>
</source>
::TextArea-->
<source lang=python>
<form action="..." method="post" target="_blank">
<textarea name="textcontent" cols="40" rows="4"/> type your text here </textarea><input type="submit" value="submit" />
</form>
</source>
::drop down box-->
<source lang=python>
<form action="/cgi-bin/dropdown.py" method="post" target="_blank">
<select name="dropdown">
<option value="Maths" selected>Maths</option>
<option value="Physics">Physics</option>
</select>
<input type="submit" value="Submit"/>
</form>
</source>
:CGI
<source lang=python>
#!/usr/bin/python
# Import modules for CGI handling
import cgi, cgitb
# Create instance of FieldStorage
form = cgi.FieldStorage()
# Get data from fields
if form.getvalue('dropdown'):
  subject = form.getvalue('dropdown')
else:
  subject = "Not entered"
print "Content-type:text/html\r\n\r\n"
print "<html>"
print "<head>"
print "<title>Dropdown Box - Sixth CGI Program</title>"
print "</head>"
print "<body>"
print "<h2> Selected Subject is %s</h2>" % subject
print "</body>"
print "</html>"
</source>
:cookies
:file upload
:file download
----
HTTP server -- programs (CGI scripts) -- interface (user input submitted through HTML<form>or<isindex>element) --> generate web content
HTTP server -- programs (CGI scripts) -- interface (user input submitted through HTML<form>or<isindex>element) --> generate web content


Line 23: Line 107:


the following code checks that the fields are set to a non-empty string
the following code checks that the fields are set to a non-empty string
<source lang=python>
  if "***" not in form or "###" not in form:
  if "***" not in form or "###" not in form:
     print "<H1>Error</H1>"
     print "Error"
     print "please fill in *** and ### fields"
     print "please fill in *** and ### fields"
     return
     return
  print "<p>***:", form["***"].value
  print "<p>***:", form["***"].value
  print "<p>###:", form["###"].value
  print "<p>###:", form["###"].value
</source>


if the submitted form data contains more than one field with the same name -->form[key] is not a FieldStorage or MiniFieldStorage instance but a list of such instances; form.getvalue(key) return a list of strings; getlist()method, always returns a list of values
if the submitted form data contains more than one field with the same name -->form[key] is not a FieldStorage or MiniFieldStorage instance but a list of such instances; form.getvalue(key) return a list of strings; getlist()method, always returns a list of values
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Link: https://docs.python.org/2/library/cgi.html
Link: https://docs.python.org/2/library/cgi.html
:https://pzwiki.wdka.nl/mediadesign/How_am_I_being_served

Latest revision as of 14:48, 4 May 2015

CGI Basics

understanding--> set up the HTTP server so that whatever a file in a certain directory is requested that file is not sent back instead it is executed as a program, and whatever that program outputs is sent back for your browser to display("Content-Type: text/html").
CGI programs can be python script, shell script, perl, c or c++ program ...
Get Method
url-->
 "content-type: text/html\r\n\r\n" 
print "<h2> Hello %s %s</h2>" % (first_name, last_name)
form-->
<form action="..." method="get"> 
<input type="text" name="..." /> 
<input type="submit" value="submit" /> 
</form>
Post Method (send information as separate message instead of a text string)
form-->
<form action="..." method="post">... </form>
checkbox-->
<form action="..." method="post" target="_blank">
<input type="checkbox" name="..." value="on"/> 
<input type="submit" value="submit" /> 
</form>
radio button-->
<form action="..." method="post" target="_blank">
<input type="radio" name="..." value="on"/> 
<input type="submit" value="submit" /> 
</form>
TextArea-->
<form action="..." method="post" target="_blank">
<textarea name="textcontent" cols="40" rows="4"/> type your text here </textarea><input type="submit" value="submit" /> 
</form>
drop down box-->
<form action="/cgi-bin/dropdown.py" method="post" target="_blank">
<select name="dropdown">
<option value="Maths" selected>Maths</option>
<option value="Physics">Physics</option>
</select>
<input type="submit" value="Submit"/>
</form>
CGI
#!/usr/bin/python

# Import modules for CGI handling 
import cgi, cgitb 

# Create instance of FieldStorage 
form = cgi.FieldStorage() 

# Get data from fields
if form.getvalue('dropdown'):
   subject = form.getvalue('dropdown')
else:
   subject = "Not entered"

print "Content-type:text/html\r\n\r\n"
print "<html>"
print "<head>"
print "<title>Dropdown Box - Sixth CGI Program</title>"
print "</head>"
print "<body>"
print "<h2> Selected Subject is %s</h2>" % subject
print "</body>"
print "</html>"
cookies
file upload
file download


HTTP server -- programs (CGI scripts) -- interface (user input submitted through HTML<form>or<isindex>element) --> generate web content 

python -m CGIHTTPSever
structure of CGI
web server, processes requests via HTTP (Hypertext Transfer Protocol)
process user input submitted through an HTML <FORM> or <ISINDEX> element
cgi_directories [' /cgi-bin', ' /htbin'] containing CGI scripts (server's special cgi-bin directory)
output - CGI script consists of two sections, separated by a blank line.
print "Content-Type: text/html" # header, telling what kind of data is following (HTML is following)
print                                          # blank line, end of headers
print "<TITLE>CGI script output</TITLE>"
print "Hello Morld"  #html, nice formatting
using cgi module
import cgitb
cgitb.enable() # display detailed reports in web browser
cgitb.enable(display=0, logdir="/path/to/logdir") #have the reports saved to files

= to get at submitted form data

FieldStorage class --> can be indexed like a Python dictionary (in operator; support the standard dictionary method keys(), and built-in function len()) 

form = cgi.FieldStorage()

the following code checks that the fields are set to a non-empty string 

 if "***" not in form or "###" not in form:
     print "Error"
     print "please fill in *** and ### fields"
     return
 print "<p>***:", form["***"].value
 print "<p>###:", form["###"].value

if the submitted form data contains more than one field with the same name -->form[key] is not a FieldStorage or MiniFieldStorage instance but a list of such instances; form.getvalue(key) return a list of strings; getlist()method, always returns a list of values 

value = form.getlist("username")
usernames = ",".join(value)

If a field represents an uploaded file ???? 

fileitem = form["userfile"]

The appropriate way to read form data values was to always use the code which checks whether the obtained value is a single value or a list of values.

compact code: 

import cgi
form = cgi.FieldStorage()
user = form.getfirst("user", "").upper()    # This way it's safe.
for item in form.getlist("item"):
    do_something(item)

Link: https://docs.python.org/2/library/cgi.html

https://pzwiki.wdka.nl/mediadesign/How_am_I_being_served
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