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CGI Programming

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close (STOCKDATA); companyData.txt. AlphaBeta,75.0,1032. EastWest,132.00,500 ... planet = ('Mars','Jupiter','Saturn')[1]; print $planet, 'n'; foreach $element ... – PowerPoint PPT presentation

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Title: CGI Programming


1
CGI Programming
2
Forms
  • Forms enable two-way flow of information
  • Three important parts
  • The FORM tag includes the URL of the scripts
    that processes the data submitted via the form
  • The Form Elements like the fields and the menus.
  • Submit button Sends the data to the CGI script
    on the server.
  • Example
  • lt FORM ACTION-http///www.allScripts.com/cgi-bin/s
    cript1.cgi METHOD POST gt
  • ltHRgt Please share your comments on the form
    layout
  • ltTEXTAREA NAMEcomments ROWS3 COLS65 WRAPgt
    COMMETSlt/TEXTAREAgt
  • lt/HRgt
  • ltINPUT TYPEsubmit VALUEPRESS TO SUBMITgt
  • lt/FORMgt

3
  • a) Layout b) script
  • data can be gathered by a CGI script and saved
    ltform methodpost actionhttp//www.allscripts
    .com/cgi-bin/script1gtform text lt/formgt
  • ltform methodget actionURLofSCRIPTgt form
    text lt/formgt
  • single line input (text, checkbox,radio,etc)
  • multi line input (text)
  • drop-down menus
  • HTML Tutorial
  • Go to the "NCSA--Beginner's Guide to HTML"
    tutorial located at
  • http//www.ncsa.uiuc.edu/General/Internet/WWW/HTML
    PrimerAll.html
  • Quick tutorial http//www.jmarshall.com/easy/cgi/

4
CGI
  • CGI Common Gateway Interface
  • A simple protocol to communicate between web
    forms and your program.
  • Quick tutorial http//www.jmarshall.com/easy/cgi/
  • CGI program can be written in any language that
    can read from STDIN, write to STDOUT, and access
    environment variables. e.g., C, Perl, Java,
    Shell.

5
CGI Programming
  • 1. Browser requests a URL
  • From the Server.
  • 2. The requested URL is a script.
  • Server executes the script.
  • 3. The CGI script may call other programs.
  • 4. CGI script passes output back to the server.
  • 5. Server passes information back to the browser.
  • 6. Browser formats and displays the information
    it receives.

Browser
Server
1
2
5
3
4
CGI-Script
Other Programs
6
6
  • Typical programming pattern1. Read input data
    from STDIN2. Processing the data3. Write the
    HTML response to STDOUT.
  • When a user submit a form, the sequence of
    variables are sent to the server in the following
    format "name1value1name2value2name3value3"
  • Standard CGI script input processing1. Split
    the string by "" and "2. Convert all ""
    characters to spaces, and
  • You can find input processing funcs in C, Perl,
    etc on the web.
  • When the http server receives a submission,
    depending on the submission method of the form,
    the server construct environment variables and
    call the CGI program specified by the form.
  • For POST method, the long string can be obtained
    by reading from STDIN. String length is in
    environment variable CONTENT_LENGTH.
  • For GET method, the string is in QUERY_STRING
  • GET has length limit. POST is more popular.

7
  • Sending HTML response back to user just write
    to STDOUTThe first line should be
    Content-Type text/htmlThen write the rest of
    the HTML contents.
  • You can send other type of data back to use, such
    as "Content-type image/gif" followed by binary
    gif file data. Not all browsers support all data
    types.
  • Sending an existing file to the user as
    response. Write the following to STDOUT
    Location response.html -- followed by a blank
    line.

8
Example 1
  • A page on the Client Side
  • ltA HREFhttp//www.somesite.com/cgi-bin/getDategt
    Display Todays Datelt/Agt
  • The script, getDate on the Server Side
  • !/bin/sh
  • echo Content-type text/plain
  • echo
  • echo "ltHTMLgtltHEADgt"
  • echo "ltTITLEgtgetDate lt/TITLEgt"
  • echo "lt/HEADgtltBODYgt"
  • today/bin/date
  • echo ltPgtTodays Date todaylt/Pgt
  • echo "lt/BODYgtlt/HTMLgt"

9
Example 2
  • Server side
  • cat isOn.cgi
  • !/usr/bin/sh
  • echo "Content-type text/html"
  • echo
  • echo "ltHTMLgtltHEADgt"
  • echo "ltTITLEgtIs On? lt/TITLEgt"
  • echo "lt/HEADgtltBODYgt"
  • isonwho grep mjones
  • if ! -z "ison"
  • then
  • echo "ltPgtmjones is logged on.lt/Pgt"
  • else
  • echo "ltPgtmjones NOT logged onlt/Pgt"
  • fi
  • echo "lt/BODYgtlt/HTMLgt"
  • The Client Side
  • ltHTMLgt
  • ltHEADERgt ltTITLEgt Is On lt/TITLEgt
  • lt/HEADERgt
  • ltBODYgt
  • ltA HREF"http//www. scu.edu/cgi-bin/isOn.cgi" Is
    Mary Jones Logged Ongt lt/Agt
  • lt/BODYgt
  • lt/HTMLgt

10
A simple perl script to show the input method used
  • !/usr/local/bin/perl
  • if (ENVREQUEST_METHOD eq GET)
  • print ltPgt The request method was ENVREQUEST_M
    ETHOD
  • print ltPgtThe data from GET was
  • ENVQUERY_STRING
  • elsif (
  • ENVREQUEST_METHOD eq POST)
  • read (STDIN,buffer,ENVCONTENT_LENGTH)

11
Parsing Form Input
  • High-lights of parsing a form input.
  • The input string should be separated into
    individual fields (separated by a ).
  • Field names and values are separated by a .
  • Blank spaces encoded as should be converted
    back to spaces.
  • Convert special characters encoded as (x
    represents a xx hexadecimal digit) back to their
    character representation.

12
Using C For CGI Programs
  • Assume the form consists of the following fields
    and the user has input Mary and chosen Two Years
  • ltPgtEnter Your name ltINPUT TYPE"text"
    NAME"theName"gtlt/Pgt
  • ltULgt
  • ltLIgt ltINPUT TYPE"radio" NAME"years" VALUE"1"
    gt One Year
  • ltLIgt ltINPUT TYPE"radio" NAME"years"
    VALUE"5"gt Two Years
  • ...
  • The string variable, buffer in the program on the
    left side contains the string
  • theNameMaryyears5
  • the string value in buffer should be parsed to
    separate the fields (and field names and values).
  • int length
  • char contentLen, buffer
  • char method getenv ("REQUEST_METHOD")
  • printf("Content-type text/html\n\n")
  • printf("lthtmlgt\n")
  • if (strcmp(method,"POST") 0)
  • printf("ltPgt POST lt/Pgt\n")
  • contentLen getenv ("CONTENT_LENGTH")
  • if (contentLen ! NULL)
  • length atoi(contentLen)
  • buffer (char ) malloc (length
    1)
  • if (buffer)
  • if (fread(buffer,1,length,
    stdin) ! length)
  • return
  • printf("ltPgt Length d content
    slt/Pgt\n",length,buffer)
  • printf("lt/htmlgt\n")

13
PERL
  • Perl is an interpreted language for scanning
    files, extracting information from those text
    files, and printing reports based on that
    information.
  • Perl is mainly used to handle text files, but can
    be used for binary files (databases), process
    manipulation, network tasks.
  • Runs on DOS and UNIX
  • Information source http//www.perl.com/perl/
  • A Simple Perl program
  • !/usr/bin/perl
  • This is a comment line
  • print Hello\n

14
Data Types
  • Scalar Values
  • days 7
  • Arrays
  • Indexed by numbers
  • _at_days ("Mon", "Tues", "Wed" )
  • Hashes
  • Indexed by key values
  • days ("M" gt "Monday", "T" gt "Tuesday")
  • overtime (days"M","5", days"T","10")
  • print days"M", "\n"
  • print "The number of over time hours on ",
    overtime"Monday"
  • _at_daysWorked _at_days
  • daysWorked _at_days
  • print "Days Worked ", daysWorked, " They are
    "
  • print daysWorked0, daysWorked1,
    daysWorked2
  • print "\n"

15
Data Types
  • Examples_at_days (31,28,31,30,31,30,31,31,30,31,30
    ,31) A list with 12 elements.days
    Last index of _at_days 11 for above listdays
    7 shortens or lengthens list _at_days to 8
    elements_at_days3,4,5 (30,31,30)_at_days'a','
    c' same as (days'a',days'c')
  • Case is significant--"FOO", "Foo" and "foo"
    are all different variables. If a letter or
    underscore is the first character after the , _at_,
    or , the rest of the name may also contain
    digits and underscores. If this character is a
    digit, the rest must be digits.

16
Processing Arrays
  • Individual elements in the array can be accessed
    using the index
  • Print Today days5
  • Print days-1 The last item in the array is
    retrieved
  • (day1) _at_days first item
  • (day1, day2) _at_days first two items
  • noOfDays _at_days length of the array
  • Print days prints the last index of the array
  • Splitting a scalar into an array
  • _at_allnames split (/,/,nameString) splits the
    values in nameString, using the delimiter (comma)
    and loads the values into the array, allNames

17
Processing Arrays
  • _at_workdays _at_days copies the days array into
    the array, workDays.
  • Retrieving the elements from an array
  • _at_result _at_workdays 1,2
  • _at_myChoices (3,4)
  • _at_workDays _at_myChoices
  • unshift (_at_workdays, oneMoreDay) adds
    oneMoreDay to the beginning of the array
  • push (_at_workdays, oneMoreDay) adds oneMoreDay
    to the end of the array
  • _at_totaldays (_at_days,_at_workDays) combines two
    arrays
  • _at_days 1,2 _at_twoDays replaces two elements in
    the arrays days.

18
Processing Hashes
  • A hash (also called associative arrays) contains
    pairs of associated elements the key (first)
    and the value (Second) pairs.
  • Example
  • days ("M" gt "Monday", "T" gt "Tuesday")
  • overtime (daysM,"5", daysT,"10")
  • Values in a hash are identified by a key (not by
    an index value).
  • Are important in writing CGI scripts using PERL
    since the form parsing routines
  • The data gathered from a form is stored in a
    hash.
  • The key in each pair is the NAME attribute the
    field name
  • The value in the pair is the data that the form
    user has typed in.

19
Processing Hashes
  • oneday days M Retrieves the value
    associated with the key M.
  • _at_holidays days M,T retrieves multiple
    values
  • _at_allValues values (days) Retrieves all the
    values
  • _at_allKeys keys (days) retrieves all keys
  • (key, value) each (days) retrieves each
    pair of key, values
  • Exists holidays M returns a true if the
    key exists in the hash

20
PERL - Some Examples
  • Running a PERL command from the command line.
  • perl -e print Hello, World!
  • A simple PERL program
  • !/usr/bin/perl
  • print Enter a line to be displayed on the
    screen
  • input ltSTDINgt
  • print input
  • print Enter first number
  • num1 ltSTDINgt
  • print Enter second number
  • num2 ltSTDINgt
  • if (num1 gt num2) print true
  • else print false
  • using a built-in function
  • strLen length(What is the length)
  • print strLen
  • Creating your own functions
  • sub total
  • total 0
  • foreach num (_at___
  • total num
  • return total
  • Calling the function total
  • print total (3,3)

21
PERL
  • File Processing
  • The following program reads two lines of data
    from
  • the file, companyData, prints the total stock
    value of
  • each company and the total stock value of all
    the
  • companies.
  • grandTotal 0
  • open (STOCKDATA, companyData.txt)
  • while (line ltSTOCKDATAgt)
  • chomp (line)
  • (compName,price,shares) split (/,/,line)
  • totVal price shares
  • grandTotal totVal
  • print Total value of compName holdings
    totval\n
  • print The total value of all stock holdings
    grandTotal\n
  • close (STOCKDATA)
  • companyData.txt
  • AlphaBeta,75.0,1032
  • EastWest,132.00,500

22
Example 3 Calculates the total and average grade
for each student.The file grades contains more
than one score for each student.
!/usr/bin/perl open (GRADES, grades) or die
Cant open grades !\n while (line
ltGRADESgt) (student, grade) split ( ,
line) gradesstudent . grade .
foreach student (sort keys grades) scores
0 total 0 _at_grades split ( ,
gradesstudent) foreach grade (_at_grades)
total grade scores average
total / scores print student grades
student \t Average average\n
23
Conditional Statements
  • If statement
  • (Sky, Space) ("Blue","Colorless")
  • if (Sky eq "Colorless" )
  • print " Not so\n"
  • elsif (sky eq "Blue")
  • print "Blue Sky \n"
  • print Sky if Sky if statement - a short
    form
  • Unless
  • unless (destination eq "New York" or
    destination eq Chicago")
  • print "Destination destination\n"
  • print "No heavy winter clothing may be
    necessary \n"

24
Loops
  • last - breaks out of the loop
  • next is like continue in C
  • count 0
  • LINE while (ltSTDINgt) LINE is a label for the
    loop
  • last LINE if // Stop on first blank line.
  • The continue block is not executed because of
    last
  • next LINE if // skip comment lines
  • print _
  • continue count
  • print count, "\n"

25
Loops
  • Iterates over a list value and sets the control
    variable to each element of the list.
  • Examples
  • _at_elements ("Earth", "Sky", "Water", "Space")
  • planet ("Mars","Jupiter","Saturn")1
  • print planet, "\n"
  • foreach element (_at_elements)
  • print element
  • print "\n"
  • days ("M" gt "Monday", "T" gt
    "Tuesday")create a hash
  • foreach keyVal (keys days)
  • print keyVal
  • print "\n" prints T M
  • foreach val (values days)
  • print val
  • print "\n" prints Tuesday Moday
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