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

Revision as of 14:42, 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 "

Hello %s %s

" % (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

@@ Line 1: / Line 1: @@
+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
+<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