Intro to Perl

1. Joseph Harnish Western Michigan VMware Users Group Intro to Perl

2. Why Perl? • Perl is used by many organizations. • Perl is available on Windows and Linux. • VMware has a SDK with Perl modules.

3. What we are going to cover. • Datatypes • Regular Expressions • File I/O

4. Basic Datatypes • Scalar – Scalars hold a single item. Scalars are denoted by a $ prefix on the variable. • Array – Arrays hold a collection of numerically index scalars. They are prefixed by an @. • Hash – Hashes are collections of key value pairs. They act like arrays but are referenced by keys.

5. Scalars can be used for numerical calculations, string manipulation, etc. Scalars

6. Code example my @array = (“one”, “two”, “three”, “four”); $array[4]=”five”; for (my $i=0; $i<=4;$i++){ print “$array[$i]\n”; } # a simpler loop foreach (@array){ print “$_\n”; } Arrays

7. Code Example: #initialize has my %simpsons=(‘Father’=>’Homer’, ’Mother’=>’Marge’,’Son’=>’Bart’, ‘Daughter’=>’Lisa’); $simpsons{‘Baby’}=’Maggie’; foreach( keys %simpsons){ print “$_ =>$simpson{$_}\n”; } Hashes

8. Regular Expressions • Way of matching a pattern • Patterns consist of literal characters, character classes and quantifiers. • Character classes will match when any character in class is present. \s whitespace, \w word character, \d digit • Quantifiers tell how much items are needed for a match.

9. Quantifiers • ? = 0 or 1 • + = 1 or more • * = 0 or more • {n} = n times • {n,m} = between m and n times (inclusive)

10. Pattern match operators • =~ binds a match or substitution to a scalar it is searching. • /pattern/ match operator—looks to see if a variable contains specified pattern • s/pattern/replace/ substitution operator—replace anything that matches a pattern with replace string • Useful flags can be added at the end of the match or substitution to modify its behavior

11. Pattern match operators (cont) • Case-insensitive flag-i matches regardless of capitalization • Global flag-g finds or replaces all occurrences, not just the first one. • $name=~/bob/i; #matches bob, Bob, BOB, etc. • $name=~s/bob/Robert/gi; #replaces all variants of bob with Robert.

12. my $string=’743-5322 233-2355 23-452’; print “String contains at least one phone number” if ($string=~/\d{3}\-\d{4}/); while($string=~/(d{3}\-\d{4})/){ print “$string\n”; } Match Example

13. search.cpan.org www.perlmonks.org www.vmware.com Additional Resources