More CGI Programming

1
More CGI Programming

• Here-docs
• Multiple Submits
• Cookies
• Emailing
• File Uploading

2
Things to Try if your CGI doesnt work

• Run your script on the command line look for
  compiler errors
• make sure proper permissions are set on file
  rwx------
• Make sure proper permissions are set on
  directory rwxr-xr-x
• look in error logs /servers/cgi2/logs/apache/erro
  r.log
• make sure Windows isnt causing problems
• dos2unix ltoldfilegt ltnewfilegt

3
Here-Doc

• A special way of printing out large amounts of
  text
• This can actually be done in any Perl program,
  but I find it most useful in CGI, when you have
  to print large amounts of HTML
• print ltltHTML_END
• lthtmlgtltheadgt
• lttitlegttitlelt/titlegt
• ltheadgt
• ltbodygt
• ...
• HTML_END

4
Here-Doc notes

• The ending Here-Doc marker must be on a line
  containing the marker followed by a newline.
  NOTHING ELSE.
• Output will be formatted exactly as you type it,
  including newlines, spaces, and tabs
• If starting marker is enclosed in double-quotes,
  or not enclosed in quotes, all variables will be
  interpolated
• If starting marker enclosed in single-quotes,
  variables will not be interpolated
• By convention, the Here-Doc marker is in all
  caps, much like File Handles.
• This is convention, not a Perl specification

5
Deciding Where to Go

• What if you want to have more than one
  functionality on your form? In other words, have
  more than one button the user can push.
• We saw last week in the dump() example that the
  name and value of the submit button are passed as
  parameters.
• This is useful.

6
Multiple Submits

• Just as you can have many different text fields
  or checkboxes, you can have different submit
  buttons
• Make sure you give each submit a different name.
• Only the submit button that is pressed will be
  passed as a parameter.
• Check to see if this parameter exists.
• ltinput typesubmit nameSubmit1 valueGo Here!gt
• ltinput typesubmit nameSubmit2 valueGo
  There!gt
• if (param(Submit1))
• elsif (param(Submit2))
• else

7
Importing Variables

• It can be tedious (and inefficient) to make
  several calls to param() to keep getting the same
  parameter value.
• Wed like to be able to refer to those parameters
  as normal Perl variables.
• Well, thanks to CGI.pm, we can
• import_names() takes current parameter list and
  creates scalar and array variable for each
  parameter name, with the parameters value(s)
• scalar is first value with that name, array is
  all
• defaults to being imported to namespace Q
• You can change it by passing a string into
  import_names()
• it wont allow you to import into main

8
import_names()

• From the inputs example last week, if outputs.cgi
  called import_names, the following variables
  would spring into existance, with the following
  values
• QMyText ? This is a text field
• _at_QMyText ? (This is a text field)
• Qfruits ? Apples
• _at_Qfruits ? (Apples, Oranges)
• (assuming both boxes were checked)
• Qcolors ? blue
• _at_Qcolors ? (blue)
• etc

9
File Uploading

• Another input method we did not talk about last
  week is a file-upload field.
• To use file-uploading feature, you must use a
  special kind of form.
• Add ENCTYPEmultipart/form-data to ltformgt
• Or, start_multipart_form() instead of
  start_form()
• ltinput typefile nameuploadedgt
• filefield(-namegtuploaded)
• Creates a field in which the user can enter the
  name of the file to send to the server. Also
  creates a Browse button to search the local
  machine.
• User enters name or path of a file to upload.
• The form is submitted, and the CGI script can
  then access this file.

10
Getting the File

• To get the name of the file the user wants to
  upload, use the param() function.
• file param(uploaded)
• If you use file as a string, it will be the name
  of the file.
• If you use file as a filehandle, it will be a
  link to the actual file.
• print Contents of file file areltbrgt\n
• foreach line (ltfilegt)
• print lineltbrgt

11
Thats Great for Text Files

• But users can upload any kind of file.
• You need to find out what kind of file it was.
• uploadInfo() function. Returns a reference to a
  hash containing info about the file.
• file param(uploaded)
• info uploadInfo(file)
• type info-gtContent-Type
• type may contain text/html, text/plain,
  image/jpeg, etc etc

12
If File is not Text

• Need a function to read from binary files.
• read(filename, buffer, size)
• filename?filehandle to read
• buffer?scalar in which to store data
• size?max number of bytes to read
• returns number of bytes read
• file param(uploaded)
• open UPLOAD, gtbinary.jpg
• while (numread(file,buf,1024))
• print UPLOAD buf
• close UPLOAD
• This is not CGI-specific. read() can be used in
  any Perl-script as an alternative to ltgt

13
Emailing from your CGI Script

• In actuality, you can use this process to email
  from any Perl program.
• I just feel like teaching it now.
• Note that this will be a Unix-specific (in fact,
  RPI CS dept specific) lecture. There are ways
  to accomplish the same thing on Windows, but
  were not going into it.

14
sendmail

• barebones emailing program. No friendly user
  interface whatsoever.
• standard with most Unix distributions.
• on RPI CS system, located in /usr/lib/
• but on cgi2.cs, located in /usr/sbin/
• We need to run it with the t flag. This tells
  the program to search the message for the To,
  Cc, Bcc, etc
• For more information, man sendmail

15
Pipes review

• As we learned weeks ago, Pipes are one way to get
  your perl script to run an external program.
• You can open a pipe to another program or process
  in almost the same way you open a file.
• A pipe is a connection between your program and
  another executable program. You can feed it
  input as though you were writing to the file
• Instead of lt, gt, or gtgt, use the character in
  front of file name.
• open (PROG, myprogram.exe) or die Cannot
  open program

16
Put Them Together

• open (MAIL, /usr/sbin/sendmail t) die
  Cannot begin mail program
• print MAIL From lallip\_at_cs.rpi.edu\n
• print MAIL To president\_at_rpi.edu\n
• print MAIL Subject I want a raise!\n
• print MAIL You know, Dr. J, Im not quite sure
  this is really worth it. \n
• close MAIL

17
Cookies

• Love them or hate them, they exist. And youll
  learn how to use them.
• learning to use them responsibly is left as an
  exercise to the reader
• A cookie is a (usually very small) piece of text
  that a server sends to a web browser for later
  retrieval.
• Can be used to track a users preferences, or
  any other information the user has told the
  server.

18
To Set a Cookie

• Create the cookie
• cookie() function. Takes many (mostly optional)
  parameters
• -namegt Name of the cookie
• -valuegt Value of the cookie can be any
  scalar, including array reference or hash
  reference
• -expiresgt Expiration date/time of the cookie
• -pathgt Path to which cookie will be returned
• -domaingt Domain to which cookie will be returned
• -securegt 1 if cookie returned to SSL only

19
Cookie Expiration

• Expires absolute or relative time for cookie to
  expire
• 30s ? in 30 seconds
• 10m ? in 10 minutes
• 1h ? in one hour
• -1d ? yesterday (ASAP)
• now ? immediately
• 3M ? in 3 Months
• 10y ? in 10 Years
• Wed, 13-Apr-2003 180000 GMT ? On Wednesday,
  4/13/2003 at 6pm GMT.

20
Cookie Path

• region of server to check before sending back
  the cookie.
• If I set a cookie with -path gt /perl/s03/
• Then only CGI scripts in /perl/f03 (and its
  subdirectories) will receive the cookie.
• By default, path is equal to the path of the
  current CGI script.
• To send cookie to all CGI scripts on server,
  specify -path gt /

21
Cookie Domain

• domain (or partial domain) to which to send
  cookie back
• must contain at least 2 periods (so one cant
  send a cookie to all .com domains)
• if I set cookies -domain gt .rpi.edu, cookie
  will be sent to scripts on www.rpi.edu,
  www.cs.rpi.edu, cgi.cs.rpi.edu, etc
• if set to .cs.rpi.edu, cookie only sent to
  www.cs.rpi.edu, cgi.cs.rpi.edu, cgi2.cs.rpi.edu,
  etc
• if set to www.cs.rpi.edu, cookie sent only to
  pages on www.cs.rpi.edu
• Note that both domain and path must match cookie
  parameters in order to be sent.

22
Cookie Created, Now Set it.

• cookie cookie( ... )
• print header(-cookiegtcookie)
• To set more than one cookie, use array reference
• cookie1 cookie (...)
• cookie2 cookie (...)
• print header(-cookiegtcookie1, cookie2)

23
Retrieve the Cookies

• Once again, use the cookie() function.
• This time, dont use any value parameters. Just
  give the name
• mycookie cookie(lallip)
• mycookie now has value of the cookie named
  lallip.

24
Coming Weeks

• HW5 due Tuesday, 4/8, 115959pm EDT
• NO CLASS Wednesay, 4/9 - GMWeek
• HW6 will be posted Wednesday, 4/9, mid-day
• Class Wednesday 4/16 is on GUI with Perl/Tk
• HW6 due Tuesday, 4/22, 115959pm EDT
• Wednesday, 4/23 is a review for the Final Exam
• Come prepared with questions
• Well do Course Evaluations first, for those who
  dont want to stay for the review.
• FINAL EXAM is Wednesday, 4/30
• 400pm-600pm, in Sage 5101 and Troy 2012