Perl Training

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Perl Training

• CGI and CGI.pm

http//perlwizard.org/perl/week6
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Agenda

• Homework Review
• CGI Environmental Variables
• Hashes
• Query String
• Getting more Information
• Getting User Input from the Query String
• CGI.pm examples
• More CGI.pm functions
• Homework!!!

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Homework Problem 1

• The fibonacci number is computed by adding one
  less than the number, and two less than the
  number. Create a program that will compute the
  fibonacci number of a number.

!/usr/local/bin/perl _at_fib (0,1) sub fib
my (n) _at__ unless defined (fibn)
fibn fibn-1 fibn-2 return
fibn
Main Program foreach num (1 ..
50) printf(The fib of 2.0f is 15.0f\n,
num, fib(num)
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Bonus Homework Problem

• Create a Perl program that makes your job easier,
  or helps you do your job more efficiently.
• Come up and present what you did!!

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CGI Environmental Variables

• ENV
• ENVVARNAME Environmental Variable named
  VARNAME
• tmp ENVREMOTE_HOST Domain name of
  computer making request
• A Couple of Others
• GATEWAY_INTERFACE CGI/1.1
• HOME /
• HTTP_ACCEPT image/gif, image/jpeg, /
• HTTP_HOST www.vservers.com
• PATH_TRANSLATED /usr/local/apache/cgi-bin
• QUERY_STRING eastern
• REMOTE_ADDR 209.124.234.223
• REMOTE_HOST ratbert.lightrealm.com
• REQUEST_METHOD GET
• SCRIPT_NAME /telltime.cgi
• SERVER_NAME www.vservers.com
• SERVER_PORT 80

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Hashes (Quick Overview)

• Hashes are just like arrays, but instead of using
  numbers as an index, they use strings (called
  keys).
• myHash () Create Empty Hash
• myHashapple Hello Using the key
  apple, assign the value Hello
• myHashcharlie Goodbye Using the key
  charlie, assign Goodbye
• tmp boy
• tmp2 forever
• myHashtmp tmp2 Using the key boy,
  assign forever
• _at_AllKeys sort(keys(myHash))
• foreach key (_at_AllKeys)
• print key myHashkey\n Prints each
  key and value in order alphabetically
• according to the key (apple, boy,
  charlie).

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The Query String

• lta href/cgi-bin/telltime.cgi?centralgtCentrallt/A
  gt
• lta href/cgi-bin/telltime.cgi?easterngtEasternlt/A
  gt
• theTime time()
• desiredTimeZone ENVQUERY_STRING
• if(desiredTimeZone eq central) theTime
  3600 Add one hour
• else theTime 7200 Add two hours

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Getting more information
Results After filling in the information, the
web browser sends the information to the
myscript.pl script. It sends the information in
a URL encoded string of the form
elementnameelementvalue. The spaces are turned
into for ease of use. The different
keyvalue pairs are seperated by . An example
QUERY_STRING could be FirstNameJasonLastName
NoblecolorBlue There are more things that are
done special (s and s have to be encoded)
to the URL string before it is sent. Most of
this is done automagically.

• HTML
• lthrgt
• ltform methodpost action/cgi-bin/myscript.plgt
• First Name ltinput nameFirstName size30gtltbrgt
• Last Name ltinput nameLastName size30gtltbrgt
• Favorite Color ltselect namecolorgt
• ltoptiongtBluelt/optiongtltoptiongtRedlt/optiongt
• lt/selectgtltbrgt
• ltinput typesubmit valueSendgt
• lt/formgt
• lthrgt

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Retrieving Info from the Query_String

• if(ENVREQUEST_METHOD eq GET)
• TheResp ENVQUERY_STRING
• Variables are in a string format
• else
• read(STDIN, TheResp, ENVCONTENT_LENGTH)
• Variables are given as standard input, of
  length ENVCONTENT_LENGTH

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Everything you need for getting user input

• sub parse_form_data
• local (FORM_DATA) _at__
• local (request_method, query_string,
  _at_key_value_pairs, key_value, key, value)
• request_method ENV'REQUEST_METHOD'
• if (request_method eq "GET")
• query_string ENV'QUERY_STRING'
• elsif (request_method eq "POST")
• read (STDIN, query_string,
  ENV'CONTENT_LENGTH')
• _at_key_value_pairs split (//,
  query_string)
• foreach key_value (_at_key_value_pairs)
• (key, value) split (//, key_value)
• value tr// /
• value s/(\dA-Fa-f\dA-Fa-f)/pack
  ("C", hex (1))/eg Replace special encoding
  with appropriate letter
• key tr// / You could use
  sprintf instead
• key s/(\dA-Fa-f\dA-Fa-f)/pack
  ("C", hex (1))/eg
• if (defined(FORM_DATAkey))
• FORM_DATAkey join ("\0",
  FORM_DATAkey, value) If its already
  defined, join it together with a null

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Using parse_form_data function

• parse_form_data (arguments)
• print ltHTMLgt\nltBODY bgcolor\argumentscolor
  \gt\n
• print Hello argumentsFirstName
  argumentsLastNameltBRgt\n
• print Welcome to my home pageltBRgt\n
• print lt/BODYgt\nlt/HTMLgt\n

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CGI 101

• The Simplest little CGI in the world
• print Content-type text/html\n\n
• print Hello world!\n

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CGI.pm

• CGI.pm (sometimes simply called CGI) is a Perl
  Module that has a lot of built in functionality
  that helps you build webpages.
• Makes building large webpages faster
• Cuts down on repetitive typing (print this, print
  that...)
• It may have the functionality you need, so all
  you need to do is call a function, instead of
  figuring it out on your own

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CGI.pm (Cont.)

• !/usr/local/bin/perl
• use CGI qw(standard)
• print header(text/plain),
• Nothing to it
• After saving this to a file (/www/cgi-bin/plaintex
  t.pl), you can run this program by going to
  http//yourserver.com/cgi-bin/plaintext.pl with a
  web browser, or logging into the server itself
  and running /www/cgi-bin/plaintext.pl. By
  default it will ask you to enter arguments, just
  hit Cntrl-D when youre done inputting variables.
• Output
• Content-type text/plain
• Nothing to it!

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CGI.pm (Cont.)

• Use the HERE document
• !/usr/local/bin/perl
• use CGI qw(standard)
• header header(text/plain)
• print ltltEOF
• header
• Ode to Perl
• Perl is the best,
• Why mess with the rest,
• Ever wanted to do CGI?
• It does it on the fly!!
• EOF

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Reading in from a file

• !/usr/local/bin/perl
• use CGI qw(standard)
• FILE /usr/tmp/press_release.txt
• open(FILE, FILE) die Cant open FILE
  !\n
• print header(text/plain)
• while(ltFILEgt)
• s/DATE/20000915/g
• print
• close FILE

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An HTML Page (via CGI.pm)

• !/usr/local/bin/perl
• use CGI qw(standard)
• current_time localtime
• print header, print Content-type
  text/html\n\n
• start_html(A virtual clock), print
  ltHTMLgtltHEADgtltTITLEgtltBODYgt
• A virtual Clocklt/TITLEgtlt/HEADgtlt/BODYgt
  
• h1(A virtual clock), print ltH1gtA
  virtual clocklt/H1gt
• The current time is current_time.,
  print the string
• hr, print ltHRgt
• end_html print lt/BODYgtlt/HTMLgt

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Adding Images with CGI.pm

• img(Attributes)
• Attributes
• align alt border height width
• hspace ismap src lowsrc vspace
• usemap
• print header,
• start_html,
• img(-srcgtimages/perl.gif, -aligngtright),
• end_html

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Adding Links with CGI.pm

• a(Attributes)
• Attributes
• href name onClick onMouseOver
• target
• print header,
• start_html,
• a(-hrefgt/perl/perl2.htm, Go to week 2),
• end_html

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Unordered Lists

• !/usr/local/bin/perl
• use CGI qw(standard)
• print header,
• start_html(Vegetables),
• h1(Eat your Vegetables),
• ol(
• li(peas),
• li(broccoli),
• li(cabbage),
• li(peppers,
• ul(
• li(red),
• li(green)
• )
• ),
• ),
• hr,
• end_html

Results Content-Type text/html lt!DOCTYPE HTML
PUBLIC "-//IETF//DTD HTML//EN"gt ltHTMLgt ltHEADgt
ltTITLEgtVegetableslt/TITLEgt lt/HEADgt
ltBODYgt ltH1gtEat your Vegetableslt/H1gt
ltOLgt ltLIgtpeaslt/LIgt
ltLIgtbroccolilt/LIgt ltLIgtcabbagelt/LIgt
ltLIgtpeppers ltULgt ltLIgtredlt/LIgt
ltLIgtgreenlt/LIgt lt/ULgt lt/LIgt lt/OLgt
ltHRgt lt/BODYgt lt/HTMLgt
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Other CGI Functions
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More CGI Functions
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More information

• http//stein.cshl.org/WWW/software/CGI/
• Examples
• http//www.wiley.com/compbooks/stein/source.html
• http//www.wiley.com/compbooks/stein/
• perldoc CGI

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Homework Problem 1

• Add a CGI frontend to your bonus program that you
  created last week

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Bonus Homework Problem

• Add another item of functionality to your bonus
  problem from last week.

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Questions?