Week Four Agenda

2. Week Four Agenda • Announcements • Link of the week • Review week three lab assignment • This week’s expected outcomes • Next lab assignment • Break-out problems • Upcoming deadlines • Lab assistance, questions and answers

3. Announcements Script Comments Scripts should contain the following comments: Editing Author: Script Functionality: Lab Assignment: Due Date:

4. Link of the Week Object Code • http://freedom-to-tinker.com/blog/felten/source-code-and-object-code • What is object code? • Object File Format • Executable File Format • What is Executable and Linking Format?

5. Link of the Week

6. Link of the Week

7. Review Week Three Lab Assignment A process associates a number with each file that it has opened. This number is called a file descriptor. When you log in, your first process has the following three open files connected to your terminal. Standard Input (stdin) : Filedescriptor 0 is open for reading. < really means <0 Standard Output (stdout): File descriptor 1 is open for writing. > really means 1> Standard Error (stderr): File descriptor 2 is open reading. >> really means 1>>

8. Review Week Three Lab Assignment Perl is a simple language that compiles and executes like a shell or batch type file. Perl doesn’t impose special growth limitations on an array or data strings Perl is a composite of C, AWK, and Basic. Perl was originally developed to manipulate text information.

9. Review Week Three Lab Assignment • Perl’s capabilities range from - System administration - Web development - Network programming - GUI development • Perl’s major features are • Procedural Programming makes use of simple sequential steps, routines, subroutines, and methods. • Object Oriented Programming (OOP) makes use of “objects”. The key elements of are inheritance, modularity, polymorphism, and encapsulation.

10. Review Week Three Lab Assignment Perl and Shell Similarities Perl scalar@ARGV ~ Shell $# Perl $ARGV[0] ~ Shell $1 Perl $ARGV[1] ~ Shell $2 Perl unless(scalar(@ARGV)==2) ~ Shell if [ $# != 2] All Perl statements are terminated with a “;” Perl exit 0 is returned if execution was successful. Perl exit 1 is returned if execution fails.

11. Review Week Three Lab Assignment Perl syntax $? - this variable contains the return value # - precedes a comment statement in Perl \n - new line syntax “ …” $strexp = “This text is considered as a string”; ‘ …’ $charexp = ‘a’; ` …` $cmdexp = `ls –l`; @ARGV – array containing command line arguments $_ - default implied scalar

12. Review Week Three Lab Assignment There are two types of relational operators. One class operates on numeric values, the other on string values. Relational operators NumericStringMeaning > gt Greater than >= ge Greater than or equal < lt Less than <= le Less than or equal

13. Review Week Three Lab Assignment Equality Operators NumericStringMeaning == eq Equal to != ne Not equal to  cmp Comparison, sign results -1 if the left operand is less 0 If both operands equal 1 If the left operand is greater

14. Review Week Three Lab Assignment Commands cal –y (display a calandar for the year) cal –j 2009 (display Julian dates) cal –m 2009 (display Monday first day) cal –s 2009 (display Sunday first day) cal 9 2009 (display September 2009 month)

15. Week Four Expected Outcomes Learning Outcomes • Write Perl scripts, including variables, control flow, and regular expression syntax

16. Next Lab Assignment • Perl is designed to - Process text data - Perform pattern matching - Utilize string handling tasks • Perl is available on many platforms - UNIX - Linux - HP-UX

17. Next Lab Assignment Perl utilizes two types of categories - Singular variables that represent a single-value. The variable prefix symbol for a scalar is the $. - Plural variables are ones that contain multiple-values. Arrays and hashes are two multi-valued variables.

18. Next Lab Assignment Perl data types $answer = 42; (an integer) $pi = 3.14159265; (a “real” number) $animal = “horse”; (string) $statement = “I exercise my $animal”; (string with interpolation) $amount = ‘It cost me $5.00’; (string without interpolation) $cwd = `pwd`; (string output from a command)

19. Next Lab Assignment @garage = (“car”, “mower”, “broom”); Definition: An array is an ordered list of scalars, accessed by the scalar’s position in the list. @persons = (“Will”, “Karim”, “Asma”, “Jay”); $count = @persons; Demonstrate: Execute week_four.pl script

20. Next Lab Assignment Open Statement The open function can be used to create file handles for different purposes (input, output, piping), you need to be able to specify which behavior you want.

21. Next Lab Assignment open functions open(file_handler, “file_name”) open(file_handler, “<file_name”) open (file_handler, “>file_name”) open (file_handler, “>>file_name”)

22. Next Lab Assignment Filehandle is utilized for both input and output files. Most file names are cryptic and are meaningless to programmers. The purpose of a filehandle is to help the programmer remember a simple file name throughout a program. A filehandle is a name given for a file, device, socket, or pipe. Filehandle command line format: open(filehandle, file name, permissions, chmod); Example: open($FH,$file_name);

23. Next Lab Assignment What is List Processing? @math_array = (6 - 4, 4 * 4, 8 / 2, 9 - 8); while ( … ) { … } for (counter = 0; counter < 10; counter++) { … } Three expressions are contained in a for loop: • Set initial state of the loop variable • Condition test the loop variable • Modify the state of the loop variable

24. Next Lab Assignment foreach VAR (List) { … } Demonstrate: Execute read_list.pl script @myNames = ('Larry', 'Curly', 'Moe');foreach (@myNames) { print $_;} Demonstrate: Execute sum_list.pl script

25. Next lab assignment Perl Program Statement #!/usr/bin/perl #!/usr/bin/perl -w Print continuation statement print "error: incorrect number of arguments", "\n", "usage: intlist a b (where a < b)", "\n"; Demonstrate: Execute linenum.pl and intlist.pl scripts.

26. Next lab assignment Demonstrate Execute arry_sort.pl script

27. Break-out problems • $strexp = “This text is considered as a string”; • $intexp = 10; • $floatptexp = 2.54; • $charexp = ‘a’; • $cmdexp = `ls –l`; • $argexp = (“two”, “four”, “six”); • @arrayexp = (“Jackie”, “Vicki”, “Alex”); • $arrayexp[0] = “new value”; • $a = $b + 5; • $container = @container; • ($map{blue}, $map{orange}, $map{jade}) = (0xff0000, 0x00ff00, 0x0000ff0);

28. Next Lab Assignment Programming Perl text book reading Chapter One Chapter Two Chapter Three

29. Upcoming deadlines Lab Assignment 3-1 is due on May 23, 2010. Lab Assignment 4-1 is due on May 30, 2010. Lab Assignment 7-1, Midterm exam administered from June 7 through 12. Midterm outline will be posted on the Bulletin Board by May 23, 2010.

30. Questions and answers • Questions • Comments • Concerns • After class, I will help students with their scripts.