Fundamentals of Web Programming

1
Fundamentals ofWeb Programming

• Lecture 9 Server-Side Scripting I

2
Todays Topics

• Review server scripting
• CGI support for Perl 5 CGI.pm
• Input/output file handles
• Example dynamic file listing
• URL support for Perl 5 LWP.pm
• Example fetch a stock quote

3
Server Scripting

• Parse Environment Information
• Prepare Response Content
• Print Return HeaderContent-type ltMIME typegt,
  e.g.Content-type text/html
• Print Return Content

4
CGI Support in Perl 5

• Perl Module CGI.pmuse CGI
• Subroutine to fetch environmentCGIReadParse()
  
• Environment variables and form element values
  stored in hashlastname inlast_name
• Support for interactive debugging

5
Quick Example

• !/usr/bin/perluse CGICGIReadParse()na
  me innameprint ltltEndTextContent-type
  text/plainName nameEndTextexit 0

6
Input/Output File Handles

• Including data in your scripts is okay if
• theres not a lot of it
• it doesnt change very often
• For larger data stores, its better to use
  separate data files
• can grow over time
• can be provided by or processed by other programs

7
Input/Output File Handles

• In Perl, file input and output are accomplished
  via filehandles
• Correspond to input / output streams in other
  languages
• Basic sequence
• open a file handle for input or output
• read/write from/to the file handle
• close the file handle

8
Input/Output File Handles

• Inputopen(IN,ltguestbook.txt) read lines
  from INclose(IN)
• Outputopen(OUT,gtguestbook.txt) write lines
  to OUTclose(OUT)

9
Input/Output File Handles

• Appendopen(OUT,gtgtguestbook.txt) append
  lines to OUTclose(OUT)
• Pipe from Commandopen(LS,ls ) read lines
  from LS commandclose(LS)

10
Input/Output File Handles

• Pipe to Commandopen(SORT, sort gt
  gbsort.txt) sort lines and save in
  gbsortclose(SORT)

11
Reading Lines In

• Once open, the file handle is accessed using ltgt
  notation and the assignment operator
• How much is read depends on the type of the LHS
  expression
• Array context _at_lines ltINgt
• Scalar context line ltINgt

12
Input Examples

• Array contextopen(IN,ltgbook.txt)_at_guests
  ltINgtclose(IN)foreach guest (_at_guests)
  print guest

13
Input Examples

• Scalar contextopen(IN,ltgbook.txt)while
  (guest ltINgt) print guestclose(IN)

14
Printing Output

• Once open, the file handle is accessed using ltgt
  notation and the print or printf command
• E.g., print OUT name\n

15
Output Examples

• open(OUT,gtgbook.txt)print OUT Start new
  file.\nclose(OUT)open(OUT,gtgtgbook.txt)pr
  int OUT Add to old file.\nclose(OUT)

16
Using Pipes

• The file handle is opened by calling another
  program and piping the results as though they
  were an input file
• E.g., open(LS,ls )
• Example script listall.cgi

17
Accessing the Web

• Fetching URLs LWP.pmuse LWPSimpleurl
  http//www.cnn.comresult get(url)
• Example quote.cgi