Perl: Lecture 2 Advanced RE & CGI. Regular Expressions 2.

Perl: Lecture 2

Advanced RE & CGI

Regular Expressions 2

Advanced Pattern Matching

Anchor Metacharacters– ^ Beginning of String– $ End of String

"housekeeper" =~ /keeper/; # matches "housekeeper" =~ /^keeper/; # no match "housekeeper" =~ /keeper$/; # matches "housekeeper\n" =~ /keeper$/; # matches "housekeeper" =~ /^housekeeper$/; # matches

Character classes

„[ ]“ notation

„-“ range of characters

„^“ negated

/[bc]at/; # matches 'bat', 'cat' "abc" =~ /[cab]/; # matches 'a' /[\]c]def/; # matches ']def' or 'cdef'

/item[0-9]/; # matches 'item0' or ... or 'item9' /[0-9a-fA-F]/; # matches a hexadecimal digit

/[^0-9]/; # matches a non-numeric character

Common Character Classes

\d digit [0-9] \s whitespace [\ \t\r\n\f] \w word character [0-9a-zA-Z_] \D negated \d [^0-9] \S negated \s [^\s] \W negated \w [^\w] '.' any character but ''\n'‚ \b word boundary \w\W or \W\w

Alternation & Grouping

„|“ alternation operator

„( )“ grouping

m//i modifier– Case-insensitive match

"cats and dogs" =~ /dog|cat|bird/; # matches "cat"

/house(cat|keeper)/

"20" =~ /(19|20|)\d\d/;

Extracting Matches

Grouped patterns can be extracted

$time =~ /(\d\d):(\d\d):(\d\d)/; $hours = $1; $minutes = $2; $seconds = $3;

($hours, $minutes, $second) = ($time =~ /(\d\d):(\d\d):(\d\d)/);

Matching repetitions

Quantifier Metacharacters– ? 0 or 1 times– * 0 or more times– + 1 or more times– {n,m} at least n, at most m times– {n,} at least n times– {n} exactly n times

/\w+/ # matches a word$year =~ /\d{4}|\d{2}/; # 2 or 4 digit years

Search and Replace

s/regex/replacement/ Syntax

replaces only one occurence– s///g modifier replaces all occurences

$x = "Time to feed the cat!";$x =~ s/cat/dog/;

$y =~ s/^'(.*)'$/$1/;

RE functions

quotemeta EXPR– escapes all RE metacharacters

split /PATTERN/, EXPR– splits a String at a delimiter specified by

PATTERN

pos SCALAR– Returns offset of last m//g occurence

Time functions

time– Returns number of seconds since jan 1, 1970

localtime– Convert time to human-readable format

($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);

gmtime– Do the same on the basis of GMT

What is CGI?

Common Gateway Interface Not a programming language Method for the web server for the invocation

of a program on a user‘s request Method of exchanging data between a user,

a web server and the program

CGI Functionality

CGI Program invoked when its URL is requested

Parameters / Data Included in the request

Setting up the web server for Perl CGI

Example Microsoft Windows, Apache HTTPD– HTTPD is preconfigured for scripts– http://host/cgi-bin– #! required (e.g. #!C:\perl\bin\perl)– Possibly delete windows file type association

CGI Data Exchange overview

Web Server

User

Perl Script

RequestGET / POST

Response

Simple CGI program

#!/usr/bin/perl

print „Content-type: text/html\n\n“;

print „<html><head></head><body>“;

print „<h1>This is CGI</h1>“;

print „</body></html>“;

CGI Environment Variables

HTTP_ACCEPT="*/*"HTTP_ACCEPT_ENCODING="gzip, deflate"HTTP_ACCEPT_LANGUAGE="en-us"HTTP_CONNECTION="Keep-Alive"HTTP_HOST="localhost"HTTP_USER_AGENT="Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)"QUERY_STRING=""REMOTE_ADDR="127.0.0.1"REMOTE_PORT="3039"REQUEST_METHOD="GET"REQUEST_URI="/cgi-bin/printenv.pl"SCRIPT_NAME="/cgi-bin/printenv.pl"SERVER_ADDR="127.0.0.1"SERVER_ADMIN="[email protected]"SERVER_NAME="ba35002"SERVER_PORT="80"SERVER_PROTOCOL="HTTP/1.1"SERVER_SIGNATURE="<ADDRESS>Apache/1.3.27 Server at ba35002 Port

80</ADDRESS>\n"SERVER_SOFTWARE="Apache/1.3.27 (Win32) PHP/4.2.3"

Generating the response

Own result

Content-type: text/html

print "Content-type: $mime_type\n\n";

RedirectionLocation: http://www.domain.com/newpage

print "Location: $url\n\n";

Getting client data to the server

Usually from an HTML form Two methods defined in HTTP

– GET Data in request URL Accessable by CGI script using QUERY_STRING env var

– POST Data after request Accessable STDIN and CONTENT_LENGTH env var

Both methods use URL-encoding– Fields separated by &, values after = sign– Space -> +– Special characters -> %xx

Where is the data? HTML Forms (1)

<form action=„URL“ method=„get/post“>

</form>

<input type=„submit“ value=„label“ />

<input type=„reset“ value=„label“ />

<input name=„name“ [type=„password“] />

Where is the data? HTML Forms (2)

<textarea name=„name“ />

<select name=„top5“ [multiple]>

<option value=„value“>Label</option>

</select>

<input type=„radio“ name=„name“ value=„value“ /> Label

<input type=„checkbox“ name=„name“ value=„value“ /> Label

<input type=„hidden“ name=„name“ value=„value“ />

GET / POST examples

GET example

POST examplePOST /cgi-bin/script.pl HTTP/1.0 Content-type: application/x-www-form-urlencoded Content-length: 26

in=hello+there&button=Send

GET /cgi-bin/script.pl?in=hello+there&button=Send HTTP/1.0

Tasks to work with data

Find out if GET or POST is usedSplit into single fieldsURL-decodeSend HTTP header w/MIME-type & data

Used for nearly every CGI script, so already build into Perl!

CGI.pm example

use CGI qw(:standard);

print header();

@names=param();

foreach $name (@names) {my @value=param($name);print “$name -> @value<br>\n";

}

Error 500?

Internal Server Error Script behaved incorrectly See Web Server Log for more details

– apache\logs\error.log

Perl: Lecture 2 Advanced RE & CGI. Regular Expressions 2.

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