Perl

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Perl
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Common Gateway Interface (CGI)

• Set of protocols through which CGI scripts
  interact with
• Web servers
• clients (e.g., Web browsers).
• These protocols often are used to generate
  dynamic Web content based on client input.

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Common Gateway Interface (CGI)

• It is "common" in the sense that
• it is not specific to any particular operating
  system or
• to any programming language
• Yet, from the beginning, Perl has been the
  language of choice for CGI programming, because
  of its powerful text-processing capabilities

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Protocol

• A set of rules to establish, maintain and close
  communications between two entities
• Networking protocols establish connections
  to/through a specific service port on the server
• An IP address and port number combination is
  necessary
• Port number implies a specific service

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Simple GET transaction

• Generated by typing a URL in your browser
• http//www.utdallas.edu/rml021000/index.html
• Which is decomposed into
• www.utdallas.edu as the IP address equivalent
• http as the protocol/type-of-service
• The directory/file combination

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HTTP request

• The browser sends an HTTP request message to the
  server.
• GET /rml021000/index.html HTTP/1.0
• The word GET indicates that the client wishes to
  get a resource.

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Server responds

• The server responds indicating the HTTP version,
  followed by a numeric code and the status of the
  transaction.
• HTTP/1.0 200 OK
• HTTP/1.0 404 Not found

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HTTP header

• If the server sends an text document the HTTP
  header is Content-type
  text/txt
• If the server sends an HTML document the HTTP
  header is Content-type
  text/html
• If the server sends an image file the HTTP header
  is
  Content-type image/gif

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Client-side browser

• The connection is terminated when the transfer of
  the resource is complete.
• The client-side browser interprets the HTML it
  receives and displays the results.

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Static Web pages

• lthtmlgt
• lttitlegt My portfolio lt/titlegt
• ltBODY BGCOLORORANGE TEXTBROWNgt
• ltpgt Hello this is my page lt/pgt
• ltpgt My name is Rafael lt/pgt
• ltpgt the date is Jul 15, 2004lt/pgt
• ltpgt This is my portfolio lt/pgt
• ltulgt
• ltligt ltA HREFproject1.htmlgtproject 1lt/Agt
• ltligt ltA HREFproject2.htmlgtproject 2 lt/Agt
• lt/ulgt
• lt/bodygt
• lt/htmlgt

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Dynamic web pages

• CGI scripts (sh, perl, c, c...) helps us in the
  creation of dynamic web pages.
• CGI allows us to redirect the output of a script
  to the server, which can send the output to a
  client's browser.

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ex1.pl localtime()

• !/usr/bin/perl
• first example
• print "Content-type text/html\n\n"
• print "ltHTMLgt"
• print "ltHEADltTITLEgtDatelt/TITLEgtlt/HEADgt"
• print "ltBODYgt"
• print scalar (localtime() )
• print "lt/BODYgtlt/HTMLgt"

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• When a Perl program is executed as a CGI script,
  the standard output is redirected to the Web
  browser client.
• To execute the program, you must place the Perl
  file in your Web server's cgi-bin directory.
• In apache this is /public_html/cgi-bin

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Executing the perl script

• You can execute the program by typing in your
  browser's Address or Location field the following
  line
• http//www.utdallas.edu/cgi-bin/cgiwrap/userid/per
  lscript
• http//www.utdallas.edu/cgi-bin/cgiwrap/rml021000/
  ex1.pl
• or
• http//www.utdallas.edu/userid/cgi-bin/perlscript
  
• http//www.utdallas.edu/rml021000/cgi-bin/ex1.pl

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ex2.pl

• !/usr/bin/perl
• print "Content-type text/html\n\n"
• print "ltHTMLgt"
• print "ltHEADgt
• print "ltTITLEgtMY PAGElt/TITLEgt"
• print "lt/HEADgt"
• print "ltBODY BGCOLORORANGE TEXTBROWNgt"
• print "ltH2gtHello, welcome to my pagelt/H2gt"
• print "ltPgt"
• print "ltFONT FACEHELVETICA COLORWHITEgtMy name
  is Rafaellt/FONTgt"
• print "lt/BODYgtlt/HTMLgt"

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Use of CGI.pm

• In the following examples, we will introduce the
  use of the CGI.pm module to generate dynamic
  HTML
• CGI.pm contains a set of functions for
  simplifying the creation of CGI scripts
• To use them we include the statement
• use CGI
• in our programs

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ex3.pl

• !/usr/bin/perl
• use CGI
• my query CGI-gtnew()
• print query-gtheader("text/html"),
• query-gtstart_html(-title gt"MY PAGE",
• -bgcolor gt ORANGE",
• -text gt BROWN"),
• query-gth2("Hello, welcome to my page"),
• query-gtp( "My name is Rafael" ),
• query-gtend_html

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ex3a.pl

• !/usr/bin/perl
• use CGI
• my query CGI-gtnew()
• print query-gtheader("text/html")
• print ltlt END_HERE
• lthtmlgtltHEADgtltTITLEgtMy PAGElt/TITLEgtlt/HEADgt
• ltBODY BGCOLORORANGE TEXTBROWNgt
• ltH2gtHello, Welcome to my pagelt/H2gt
• ltPgt My name is Rafaellt/Pgt
• lt/BODYgt
• lt/HTMLgt
• END_HERE

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import tag standard

• It denotes the standard function set within
  CGI.pm
• qw operator to make it easy to add additional
  tags or functions later
• Functions (such as header) can be called directly
  (without prefix)

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ex4.pl

• !/usr/bin/perl
• use CGI qw(standard)
• print header("text/html"),
• start_html(-title gt"MY PAGE",
• -bgcolor gt ORANGE",
• -text gt BROWN"),
• h2("Hello, welcome to my page"),
• p( "My name is Rafael" ),
• end_html

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HTML forms to send input

• HTML provides the ability to include forms to
  input information to be sent to a CGI script
• The ltformgt tag takes two attributes
• action, The call to a CGI script to process the
  form data
• method, which normally is either GET or POST

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ex5.html

• ltHTMLgt
• lttitlegtCGI TESTlt/titlegt
• ltBODYgt
• ltpgtWrite your name
• ltform method "get" action"http//www.utdallas.e
  du/cgi-bin/cgiwrap/mxs015000/ex5.pl"gt
• ltinput type"text" name"word"gt
• ltinput type"submit" value"submit word"gt
• lt/formgt
• lt/BODYgt
• lt/HTMLgt

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ENV and QUERY_STRING

• The ENV hash is a built-in hashtable in Perl
  that contains the names and values of all the
  environment variables
• Using GET with an HTML form passes data to the
  CGI script through an environment variable
  (QUERY_STRING)

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ex5.pl

• !/usr/local/bin/perl
• use warnings
• use CGI qw(standard )
• our ( name, value ) split( '',
  ENV'QUERY_STRING' )
• print header(),
• start_html(-title gt'Results')
• if ( name eq 'word' )
• print p ('Your word is ', b(value))
• print end_html

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split

• The environment variable QUERY_STRING provides
  data to my CGI script by appending it to a URL in
  a GET request, following a question mark (?)
• http//www.utdallas.edu/rml021000/cgi-bin/ex5.pl
  ?wordTechnology
• We call split to break the pair at the equals
  sign into a name and a value

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ex6.pl

• !/usr/bin/perl
• use warnings
• use CGI qw( standard )
• our ( name, value ) split( '', ENV
  'QUERY_STRING' )
• print name
• print header(),
• start_html(-title gt'Using GET with
  forms')
• print p( 'Write your name ' )
• print 'ltform method "get" action"http//www.utd
  allas.edu/cgi-bin/cgiwrap/mxs015000/ex6.pl"gt',
• 'ltinput type"text" name"word"gt',
• 'ltinput type"submit" value"submit
  word"gt',
• 'lt/formgt'
• if ( name eq 'word' )
• print p ('Your word is ', b(value))
• print end_html

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GET vs. POST

• The GET method passes data to the CGI script via
  the QUERY_STRING variable
• A GET request sends form contents as part of the
  URL, a POST request posts form contents to the
  end of the HTTP request
• A GET request can be cached by the browser on the
  client, a POST cant

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POST method

• The POST method sends data to the CGI script via
  standard input (still in name-value pairs
  connected by equals signs)
• Function read is used to read from standard input
  CONTENT_LENGTH characters and store them in the
  data variable
• data is the source for the split, instead of
  QUERY_STRING

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ex7.pl

• !/usr/bin/perl
• use warnings
• use strict
• use CGI qw( standard )
• our ( data, name, value )
• read( STDIN, data, ENV 'CONTENT_LENGTH' )
• ( name, value ) split( '', data )
• print header(), start_html( 'Using POST with
  forms' )
• print p( 'Enter one of your favorite words here
  ' )
• print 'ltform method "POST" action ex7.pl"gt'
• print 'ltinput type "text" name "word"gt'
• print 'ltinput type "submit" value "Submit
  word"gt'
• print 'lt/formgt'
• if ( name eq 'word' )
• print p( 'Your word is ', b( value ) )
• print end_html()

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Using CGI.pm shortcuts

• Function param takes as argument the name of the
  form field and returns its value
• No read, split or URL decoding is required and
  param works with GET or POST

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ex8.pl

• !/usr/bin/perl
• use warnings
• use CGI qw( standard )
• my word param( "word" )
• print header(), start_html( 'Using CGI.pm with
  forms' )
• print p( 'Enter one of your favorite words here
  ' )
• print start_form(), textfield( "word" )
• print submit( "Submit word" ), end_form()
• print p( 'Your word is ', b( word ) ) if word
• print end_html()

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Shortcut functions

• start_form generates the ltformgt tag and defaults
  to the POST method. If no action is given
  explicitly, the script calls itself
• textfield generates HTML equivalent to ltinput
  type text name wordgt
• submit creates a submit button with the argument
  as label

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cgi-env.pl

• !/usr/bin/perl -wT
• use strict
• my env_info (
• SERVER_SOFTWARE gt "the server software",
• SERVER_NAME gt "the server hostname
  or IP address",
• GATEWAY_INTERFACE gt "the CGI specification
  revision",
• SERVER_PROTOCOL gt "the server protocol
  name",
• SERVER_PORT gt "the port number for
  the server",
• REQUEST_METHOD gt "the HTTP request
  method",
• PATH_INFO gt "the extra path info",
• PATH_TRANSLATED gt "the extra path info
  translated",
• DOCUMENT_ROOT gt "the server document
  root directory",
• SCRIPT_NAME gt "the script name",
• QUERY_STRING gt "the query string",
• REMOTE_HOST gt "the hostname of the
  client",

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cgi-env.pl

• REMOTE_ADDR gt "the IP address of the
  client",
• AUTH_TYPE gt "the authentication
  method",
• REMOTE_USER gt "the authenticated
  username",
• REMOTE_IDENT gt "the remote user is
  (RFC 931) ",
• CONTENT_TYPE gt "the media type of the
  data",
• CONTENT_LENGTH gt "the length of the
  request body",
• HTTP_ACCEPT gt "the media types the
  client accepts",
• HTTP_USER_AGENT gt "the browser the
  client is using",
• HTTP_REFERER gt "the URL of the
  referring page",
• HTTP_COOKIE gt "the cookie(s) the
  client sent"
• )

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cgi-env.pl

• print "Content-type text/html\n\n"
• print ltltEND_OF_HEADING
• ltHTMLgt
• ltHEADgt
• ltTITLEgtA List of Environment
  Variableslt/TITLEgt
• lt/HEADgt
• ltBODYgt
• ltH1gtCGI Environment Variableslt/H1gt
• ltTABLE BORDER1gt
• ltTRgt
• ltTHgtVariable Namelt/THgt
• ltTHgtDescriptionlt/THgt
• ltTHgtValuelt/THgt
• lt/TRgt
• END_OF_HEADING

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cgi-env.pl

• my name
• Add additional variables defined by web server
  or browser
• foreach name ( keys ENV )
• env_infoname "an extra variable
  provided by this server"
• unless exists env_infoname
• foreach name ( sort keys env_info )
• my info env_infoname
• my value ENVname "ltIgtNot
  Definedlt/Igt"
• print "ltTRgtltTDgtltBgtnamelt/Bgtlt/TDgtltTDgtinfolt/TDgt
  ltTDgtvaluelt/TDgtlt/TRgt\n"
• print "lt/TABLEgt\n"
• print "lt/BODYgtlt/HTMLgt\n"