Prof. Alfred J Bird, Ph.D., NBCT Door Code for IT441 Students – * Office – Wheatly 2nd floor Office Hours – MW 3:00PM to 4:00PM

 Perl normally treats lines beginning with a # as a comment.  Get in the habit of including comments with your code.  Put a comment block at the beginning of your code which includes your name, the name of the module, date written and the purpose of the code.

#!/usr/bin/perl -w # #Module Name: helloWorld.pl # #Written by Alfred J Bird, Ph.D., NBCT #Date Written – 21 September 2011 #Purpose: To print out the string “Hello world!” # #Date Modified – 25 September, 2011 #Purpose of modification: To fix spelling errors. #Modified by: Al Bird # print “Hello world! \n”;

 To find out how many elements are in an array:  my $lastIndex = $#array  push() and pop()  Adds and removes elements from the high end of the array  shift() and unshift()  Adds and removes elements from the low end of the array

 Write a program to create an array with the names of the first six months in it and then print them out.  Modify the program using push to add the next six months one at a time to the array.  Print out the array each time including the index of the last element.  Experiment with the pop, shift and unshift functions.

 Given a text file (i.e. gettysburg.txt in my home directory) write a program to find if the a given word is used in the file.  Use the split function as such:  my $word (split)  This will break up the line into words separated by whitespace characters  If the word is found, print out a message indicating such.

 Given a text file (i.e. gettysburg.txt in my home directory) write a program to find if the a given word is used in the file.  Use the split function as such:  my $word (split)  This will break up the line into words separated by whitespace characters  If the word is found, print out a message indicating such.  Go to readAndPrint1.pl in my directory for a solution.

 Often called regex  One of the most useful features of Perl  Available in most programming languages  You used it in BASH  What does this do?  s/abc/ABC/  Welcome to the world of regular expresions

 Given a text file (i.e. gettysburg.txt in my home directory) write a program to find if the a given word is used in the file.  Use a regular expression such as  /and/  If the word is found, print out a message indicating such.

 Given a text file (i.e. gettysburg.txt in my home directory) write a program to find if the a given word is used in the file.  Use a regular expression such as  /and/  If the word is found, print out a message indicating such.  Go to readAndPrint.pl in my directory for a solution.

 What is different between the two methods of searching?  What if I want to ignore the case of the letters?  How would you modify the readAndPrint1.pl program to check without regard to capitalization?  It is not very easy is it!  With regular expressions it is much simpler.  /$word/i

 What if I wanted to find a pattern only at the start of a line or at the end of a line?  In a Regex we can use anchors.  To indicate the pattern must be at the start of a line we use the ^  i.e. /^The/  To indicate the pattern must be at the end of the line we use the anchor $  i.e./end$/

 We can make our Regex more general by using metacharacters.  See the table on page 167 in the text  Four of the more common metacharacters are: .Matches any character except newline  ? Preceding character or group may be present 0 or 1 time  +Preceding character or group is present 1 or more times  *Preceding character or group may be present 0 or more times

 Write a program that:  Reads the file alice.txt in my home directory  Checks to see if any given word is present without regard to capitalization  Modify the program to see if there are any numbers in the file

 Modify the earlier program to accept a file name as input and check for a word entered from the keyboard in the file.

 Read pages 153 to 177 in the textbook.