Perl tutorial http://www.iki.fi/o/perltut

1. Perl tutorialhttp://www.iki.fi/o/perltut • Perl reference http://www.rexswain.com/perl5.html

2. Perl tutorial What is Perl good for?

3. Perl tutorial What is Perl good for? • Small programs • Text file processing • Scripts

4. Perl tutorial Running programs

5. Perl tutorial Running programs • perl myprogram.perl • ./myprogram.perl

6. Perl tutorial Running programs • ./myprogram.perl #!/usr/bin/perl chmod +x myprogram.perl

7. Perl tutorial Running programs • perl -e “print 1+2;” • echo “print 1+2;” | perl

8. Perl tutorial Running programs • cat inputdata.txt | ./myprogram.perl

9. Perl tutorial Running programs • cat inputdata.txt | ./myprogram.perl > outputdata.txt

10. Perl tutorial Running programs • ./myprogram.perl -i inputdata.txt -o outputdata.txt

11. Perl tutorial Programming • emacs myprogram.perl &

12. Perl tutorial Programming #!/usr/local/bin/perl print (“Hello world\n”);

13. Perl tutorial Programming #!/usr/local/bin/perl print (“Hello world\n”);

14. Perl tutorial Programming #!/usr/local/bin/perl print (“Hello world\n”);

15. Perl tutorial Programming #!/usr/local/bin/perl print (“Hello world\n”);

16. Perl tutorial Programming #!/usr/local/bin/perl print “Hello world\n”;

17. Perl tutorial Variables • Scalars • Lists/arrays • Hashes

18. Perl tutorial Variables • Scalars $myvariable

19. Perl tutorial Variables • Scalars $myvariable

20. Perl tutorial Variables • Scalars $x = “100.000\n”; print $x; $x = $x + 1; print $x;

21. Perl tutorial Variables • Scalars $x = “100.000\n”; #string print $x; $x = $x + 1; print $x;

22. Perl tutorial Variables • Scalars $x = “100.000\n”; print $x; #string $x = $x + 1; print $x;

23. Perl tutorial Variables • Scalars $x = “100.000\n”; print $x; $x = $x + 1; #number print $x;

24. Perl tutorial Variables • Scalars $x = “100.000\n”; print $x; $x = $x + 1; print $x; #string

25. Perl tutorial Variables • Lists/arrays • @myarray • $myarray[0] • (1721, 2974, “blah”) • @myarray[0, 1, 2] • @myarray[0..2]

26. Perl tutorial Variables • Lists/arrays @names = (“Adam”, “Eve”); print($names[0].” likes “.$names[1]);

27. Perl tutorial Variables • Lists/arrays • scalar(@myarray) • $myarray[$x][$y] • @sortedcopy = sort(@myarray)

28. Perl tutorial Variables • Hashes • &myhash • $myhash{“blah”} • $myhash{$key1} = $value1;

29. Perl tutorial Variables • Hashes $darker{“white”} = “grey”; $darker{“grey”} = “black”; print ($darker{“white”}. “ is darker than white.”);

30. Perl tutorial Variables • Hashes • delete($myhash{$key}); • ($key, $value) = each(%myhash); • @mykeys = keys(%myhash); • @myvalues = values(%myhash);

31. Perl tutorial Program flow • Blocks { statement1; statement2; }

32. Perl tutorial Program flow • Conditionals if ($x == $y) { #... } elsif ($x == ($y+1)) { #... } else { #... }

33. Perl tutorial Program flow • Conditionals • True 1, (“a”, “b”), “ “, “hello”, “00” • False 0, (), “”, “0”

34. Numbers == != < > Perl tutorial Program flow • Conditionals Strings eq ne lt gt

35. and or negation Perl tutorial Program flow • Conditionals && || !

36. Perl tutorial Program flow • Loops for ($t = 0; $t < 100; $t++) { #... }

37. Perl tutorial Program flow • Loops while ($x == $y) { #... }

38. Perl tutorial Program flow • Loops do { #... } while ($x == $y);

39. Perl tutorial Program flow • Loops foreach $key = keys(&myhash) { #... }

40. Perl tutorial Program flow • Loops • last; • next;

41. Perl tutorial File handling • Handles • STDIN • STDOUT

42. Perl tutorial File handling open (INPUTFILE, “inputdata.txt”); open (OUTPUTFILE, “>outputdata.txt”); while ($line = <INPUTFILE>) { print(OUTPUTFILE $line); } close(OUTPUTFILE); close(INPUTFILE);

43. read read write, create write, append read, write pipe to command pipe from command Perl tutorial File handling • Opening “filename” “<filename” “>filename” “>>filename” “+>filename” “| command” “command |”

44. Perl tutorial File handling • Tests if (-e “filename”) { #File exists... }

45. readable executable exists is a directory is a tty is a text file Perl tutorial File handling • Tests -r -x -e -d -t -T

46. Perl tutorial Command line arguments • @ARGV • scalar(@ARGV)

47. Perl tutorial Subroutines sub a_plus_b { exit($_[0] + $_[1]); } print(“1+2=“.&a_plus_b(1, 2));

48. Perl tutorial Typical Bugs • Mistyped identifiers • Forgetting $ etc. • Mixing strings and numbers • Forgetting that variables are global

49. Perl tutorial Additional features • Useful functions (mathematics, strings, etc.) • ($a, $b) = split(“ “, “12 13”); • Regular expressions • UNIX system interaction • Networking • System VIPC (???) • Debugger