User:Emily/Prototyping/Trimester 03/03
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> </source>
- 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)