Cookies & file i/o in perl

Cookies & file i/o in perl

Survey (html form in notes)

Submit (Post) and anchor tag in form • Submit calls a perl program to process the data passed in a query string. Perl program opens data file, writes results to it. • In slide notes • There is an anchor at the bottom of the form which points to another perl program which displays survey results.

View survey results: another perl program

Perl program displays results • In slide notes. • You’ll need to create a data file, too, and put it in cgi-bin directory. • I saved a blank data file to get started. It is named survdat.dat

Write to file • Need to open file for output • Need to lock file • Now write to file using print fhandle string • Unlock file • Close file

Write to file #!c:\perl\bin\perl.exe print "Content-Type: text/html\n\n"; $LOCK = 2; $UNLOCK = 8; open(SURVDAT, ">somedat.dat") or error(); flock(SURVEY, $LOCK); # Write out the file data, unlock the file, and close it for ($j = 0; $j<= 20 ; $j++) { print "writing to file: $line \n"; print SURVDAT "Bob+$j $j A\n"; } flock(SURVDAT, $UNLOCK); close(SURVDAT);

Write to file

Form processing and a file

Form processing and a file • Get old file contents into an array or some other structure (open file for read, lock, read, unlock, close) • Get user data from query string • Add it to the data from the file • Open file for writing • Write the new data

File display (in notes)

File update (in notes) I did not do it precisely as per earlier notes, but used text page 408 notes to open a file for updating Open(FILEHANDLE,”+<filething”) or die “cant open”; #read from file using chomp chomp(….) #rewind to start of file seek(FILEHANDLE,0,0) or die… #then print to file

Cookies • http is stateless, so after a browser interacts with a server, no one has any memory of what happened, unless a resord of some sort is made. • Data could be written to a file for instance, as in the previous example. • Since servers may want remember client profile or shopping cart, cookies provide a mechanism of storing the information on the browser itself. • The server asks for and can look at this information if the browser returns.

Cookies • A browser makes a request to a server • A server makes a response. • The response header may include cookies. • A cookie has a name and a text value. • Every HTTP communication between a browser and a server has a header. • A CGI program can create a cookie. • The request-response cycle can include cookies being passed back and forth.

Cookies • When it is create a cookie is assigned a lifetime. • The browser deletes the cookie when its lifetime expires. • Only the server that created the cookie can receive the cookie back. • You can change your browser settings to reject or delete cookies.

Cookies • CGI.pm includes support for cookies through the cookie function. • It can create or retrieve cookies. • Form to create a cookie: cookie(-name->cookiename,-value->cookievalue,-expires->atimevalue) • Name can be any string. Value can be any scalar, including references to hashes and arrays. Expires may be expressed in many different time units. +3d means 3 days. Also s for seconds, m for minutes, h for hours, M for months, y for years and now for right now. • Cookies can be placed before print content-type in programs that don’t use CGI package, but that is not covered here.

Cookies • A cookie must be placed in the header at the time the header is created. It is passes as a parameter to the header with CGI.pm: • Header(-cookie=>$my_cookie); • I f cookie is called with no parameters it returns a hash of all the cookies in the HTTP header of the current request. • To get one specific cookie, the function is called with just that cookie name. $age=cookie(‘age’);

Cookies • To display all the cookies we could use foreach $name (keys cookie()){ print “$name \t cookie($name) ”;}

A really simple cookie example • The next example (2 perl programs) shows how to set and get a cookie with CGI. • It is about as simple as it could be.

Perl to set cookie (‘username’) #!c:\perl\bin\perl.exe use CGI ":standard"; $name = "bob"; $to_set = cookie(-name => "username", -value => $name, -expires => "+3d"); print header(-cookie => $to_set); print start_html("Thanks bob!"); print "other content"; print end_html();

Setting bob cookie

Get bob cookie

Get a cookie (named “username”) #!c:\perl\bin\perl.exe use CGI ":standard"; $name = cookie("username"); print header(), start_html("Hello $name"), h1("Hello " . $name || "Stranger"); if ($name) { print p("See, I remembered your name!"); } else { print p("The cookie must have expired."); } print end_html();

Getting time information for a cookie that checks when you last visited #!C:\perl\bin\perl.exe print "Content-Type: text/html\n\n"; ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdst) = localtime; print "\$sec = $sec\n"; print "\$min = $min\n"; print "\$hour = $hour\n"; print "\$mday = $mday\n"; print "\$mon = $mon\n"; print "\$year = $year\n"; print "\$wday = $wday\n"; print "\$yday = $yday\n"; print "\$isdst = $isdst\n";

Time.pl

Cookies: code in notes

Day_cookie.pl #!c:\perl\bin\perl.exe # day_cookie.pl # - A CGI-Perl program to use a cookie to remember the # day of the last login from a user and display it when run use CGI ":standard"; # Get the existing day cookie, if there was one @last_day = cookie('last_time'); # Get the current date and make the new cookie $day_of_week = (qw(Sunday Monday Tuesday Wednesday Thursday Friday Saturday)) [(localtime)[6]]; $month = (qw(January February March April May June July August September October November December)) [(localtime)[4]]; $day_of_month = (localtime)[3]; @day_stuff = ($day_of_week, $day_of_month, $month); $day_cookie = cookie(-name => 'last_time', -value => \@day_stuff, -expires => '+5d');

Day_cookie.pl # Produce the return document # First, put the cookie in the new header print header(-cookie => $day_cookie); print start_html('This is day_cookie.pl'); # If there was no day cookie, this is the first visit if (scalar(@last_day) == 0) { print "Welcome to you on your first visit to our site ";} # Otherwise, welcome the user back and give the date of # the last visit else { ($day_of_week, $day_of_month, $month) = @last_day; print "Welcome back! ", "Your last visit was on ", "$day_of_week, $month $day_of_month ";}

Keeping track of the shopping cart (html in slide notes)

Perl displays old (shopping cart) cookie and adds new shopping cart to it

Most of the perl program @shopping_cart = cookie('cart'); # Produce the return document my @cart= (param("cruise"), param("food"),param("music")); if (scalar(@shopping_cart) != 0) {@new_cart=(@shopping_cart,@cart);} else {@new_cart=@cart;} $the_cookie = cookie(-name => 'cart', -value => \@new_cart, -expires => '+5d'); # First, put the cookie in the new header print header(-cookie => $the_cookie); print start_html('This is cookies.pl'); # If there was no cookie, this is the first visit if (scalar(@shopping_cart) == 0) { print "Welcome to you on your first visit to our site ";} # Otherwise, welcome the user back and give the date of # the last visit else { foreach $name (@new_cart) {print "$name ";} }

Cookies & file i/o in perl