Perl Programming - 01 Basic Perl

Perl Programming
1
Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446

Danairat T.
Contents
Module-1: Introduction to Perl Programming
• Basic Variables; string, number, array, hash
• Basic Program Flows; if, unless
• Basic Program Loops; while, for, for each, do,
until
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Danairat T.
Contents
Module-2: Regular Expression
• Introduction to Regular Expression
• Matching pattern
• Special characters handling
• Substitute
• Global substitutions
3

Danairat T.
Contents
Module-3: File Handling
• Open file for Read or Write
• Close file handle
• File handle Manipulation
• Using regular expression in file handling
4

Danairat T.
Contents
Module-4: Connecting to Database
• Understand Perl built-in associate array file
• Using module Perl DBI
• Connection to MySQL or Oracle database
• Insert/Update/Delete/Select by Perl
5

Perl Programming
01 - Introduction to Perl Programming
6
Danairat T.
Line ID: Danairat
+668-1559-1446

Danairat T.
What is Perl?
(Practical Extraction and Report Language )
• Perl, release in 1987, is a high-level
programming language written by Larry Wall.
Perl's process, file, and text manipulation
facilities make it particularly well-suited for
tasks system utilities, system management
tasks, database access, networking. These
strengths make it especially popular with
system administrators.
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Danairat T.
Which version of Perl should I use?
• No one is actively supporting Perl 4. Five years ago it
was a dead camel carcass
• There is no Perl 6 release scheduled.
• The immediate releases are Perl 5.8 (i.e. Perl5.8.x )
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Danairat T.
OS Platforms Support
• UNIX: More or less every UNIX or UNIX-like operating system ever created, notably
Linux , Solaris, AIX, IRIX, HP/UX, BSD, and Tru64
• MS Windows: DOS, Windows 3.1, 95, 98, NT and 2000
• Other Desktop OSs: Apple Macintosh (68k and PPC, both pre and post MacOS X),
Acorn Risc OS, Amiga, BeOS, OS/2, and many others
• Mainframes: AS/400, OS390, VMS and OpenVMS, Stratus (VOS), and Tandem
• PDAs: EPOC (Psion/Symbian), but not PalmOS or Windows CE at time of writing,
although porting efforts are being made for both platforms
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Identify the Perl version
• perl –v
• perl -V
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www.CPAN.org
• CPAN stands for
Comprehensive Perl
Archive Network,
containing libraries,
documentation, and many
Perl third-party modules
and extensions
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Danairat T.
Install Perl
• On Unix System
– pkgadd -d /cdrom/sol_10_1009_x86/Solaris_10/Product SUNWperl584core
– pkgadd –d /cdrom/sol_10_1009_x86/Solaris_10/Product SUNWperl584usr
– pkgadd –d /cdrom/sol_10_1009_x86/Solaris_10/Product SUNWperl584man
• On Windows System
– run ActivePerl-5.8.9.826-MSWin32-x86-290470.msi
Available for download at www.activestate.com
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Danairat T.
Perl file structure and location
• Perl executable: /usr/perl5/bin/perl or /usr/bin/perl
• Perl Pain Old Documentation: /usr/perl5/pod
• Perl Manual: /usr/perl5/man
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Perl Libraries (Perl Modules)
• The Perl Libraries directories
– /usr/perl5/5.8.4/lib/i86pc-solaris-64int
– /usr/perl5/5.8.4/lib
– /usr/perl5/site_perl/5.8.4/i86pc-solaris-64int
– /usr/perl5/site_perl/5.8.4
– /usr/perl5/site_perl
– /usr/perl5/vendor_perl/5.8.4/i86pc-solaris-64int
– /usr/perl5/vendor_perl/5.8.4
– /usr/perl5/vendor_perl
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Perl Library (The modules for Unix)
http://www.cpan.org/modules/01modules.index.html
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Perl Library (PPM modules for windows)
http://ppm.activestate.com/PPMPackages/zips/8xx-builds-only/Windows/
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Install Perl Modules on Unix
gzip -dc yourmodule.tar.gz | tar -xof -
cd /your/new/lib/to/install/
perl Makefile.PL
make
make test
make install
Or, if you have internet access
perl -MCPAN -e shell
cpan> i /Time/
cpan> install Time::CTime
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Danairat T.
Install Perl Modules on Unix
bash-3.00# cd /tmp/Class-Simple-0.19
bash-3.00# perl Makefile.PL
Checking if your kit is complete...
Looks good
Writing Makefile for Class::Simple
bash-3.00# /usr/ccs/bin/make
cp lib/Class/Simple.pm blib/lib/Class/Simple.pm
Manifying blib/man3/Class::Simple.3
bash-3.00# /usr/ccs/bin/make test
PERL_DL_NONLAZY=1 /usr/bin/perl "-MExtUtils::Command::MM" "-e" "test_harness(0,
'blib/lib', 'blib/arch')" t/*.t
t/anon.............ok
t/attributes.......ok
t/Class-Simple.....ok
t/inherit..........ok
t/isa..............ok
t/nonew............ok
t/override.........ok
All tests successful.
Files=13, Tests=95, 3 wallclock secs ( 0.99 cusr + 0.52 csys = 1.51 CPU)
bash-3.00# /usr/ccs/bin/make install
Installing /usr/perl5/site_perl/5.8.4/Class/Simple.pm
Installing /usr/perl5/5.8.4/man/man3/Class::Simple.3
Writing /usr/perl5/site_perl/5.8.4/i86pc-solaris-64int/auto/Class/Simple/.packli
st
Appending installation info to /usr/perl5/5.8.4/lib/i86pc-solaris-64int/perlloca
l.pod
bash-3.00#
Example:-
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Danairat T.
Install Perl Module on Windows
1. Unzip the lib file
2. Cd to the downloaded lib
3. ppm install yourdownloadedlib.ppd
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Danairat T.
Perl Programming Structure
#!/usr/bin/perl
print "Hello, world!n"; # print to the console
• Declarations and Statements
• Semicolons
• Whitespace
• Comments
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Danairat T.
Syntax Check and Warning
#!/usr/bin/perl
use strict;
use warnings;
print "Hello, world!n";
exit (0); # The 0 is to exit the program with success, 1 is to exit with failure
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The strict checks for unsafe programming constructs. Strict forces a
programmer to declare all variables as package or lexically scoped variables.
The programmer also needs to use quotes around all strings, and to call
each subroutine explicitly.
The warnings print warnings when the Perl compiler detects a possible
typographical error and looks for potential problems with mainly look for the
most common syntax mistakes and common scripting bugs

Danairat T.
Basic variable - String
• Strings are sequences of characters.
• String literals are usually delimited by either
single (') or double quotes (").
• Double-quoted: To interpret backslash and
variable
• Single-quoted: Not to interpret backslash and
variable except and '
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Danairat T.
Double-Quoted String Representations
Code Meaning
nnnn Newline
rrrr Carriage return
tttt Horizontal tab
Backslash
"""" Double quote
b Backspace
u Force next character to uppercase
l Force next character to lowercase
U Force all following characters to uppercase
L Force all following characters to lowercase
Q Backslash all following non-alphanumeric characters
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Danairat T.
• Examples
#!/usr/bin/perl
use strict;
use warnings;
print 'tThis is a single quoted string.n';
print "tThis is a double quoted string.n";
exit(0);
StringEx01.pl
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Danairat T.
• Examples
#!/usr/bin/perl
use strict;
use warnings;
print "C:WINNTProfilesn";
print 'C:WINNTProfiles ', "n";
exit(0);
StringEx02.pl
25

Danairat T.
• Examples
#!/usr/bin/perl
use strict;
use warnings;
print " "Hi," said Jack. "Have you read Slashdot today?" ";
exit(0);
StringEx03.pl
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Danairat T.
• Examples
#!/usr/bin/perl
use strict;
use warnings;
print ' "Stop," see this. ', "n";
exit(0);
StringEx04.pl
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Danairat T.
Quote Constructs
Customary Generic Meaning Interpolates
'''''''' q//q//q//q// Literal string No
"""""""" qqqqqqqq//////// Literal string Yes
() qw// Word list No
// m// Pattern match Yes
s/// s/// Pattern substitution Yes
y/// tr/// Character translation No
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Danairat T.
• The use of q for single quote and qq for double
qoute
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
print q/"Hi," said Jack. "Have you read Slashdot today?"/ . qq/n/;
print q|"Hi," said Jack. "Have you read Slashdot today?"| . qq|n|;
print q#"Hi," said Jack. "Have you read Slashdot today?"# . qq#n#;
print q("Hi," said Jack. "Have you read Slashdot today?") . qq(n);
print q<"Hi," said Jack. "Have you read Slashdot today?"> . qq<n>;
exit(0);
StringEx05.pl
29
Results:-
"Hi," said Jack. "Have you read Slashdot today?"

Danairat T.
• The use of qw for array initialization
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
my @array1 = ('a', 'lot', 'of', 'quotes', 'is', 'not', 'very', 'legible');
print $array1[1] . "n";
# same result by using the qw and the qw will not interpolate variables
my @array2 = qw(a lot of quotes is not very legible);
# same result
my @array3 = qw(
a lot
of quotes
is not
very legible
);
exit(0);
StringEx06.pl
30
Results:-
lot
lot
lot

Danairat T.
• The use of print <<EOF to write an amount of text within your
program. Perl will interpret as double quote. This can be used
as a format print loop purpose.
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
print<<EOT;
This is a here-document. It starts on the line after the two arrows,
and it ends when the text following the arrows is found at the beginning a
line, like this
EOT
exit(0);
StringEx07.pl
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Danairat T.
The $ sign for scalar variable
• Perl use $ represent scalar variable for both
string and number.
32
$theString = “test string”;
$theNumber = 25;
#!/usr/bin/perl
use strict;
use warnings;
my $theString = "test string";
print $theString . "n"; # The . is an concatenate and n is new line
exit(0);
ScalarVarEx01.pl
Results:-
test string

Danairat T.
Scope of variable my, local
• my
The variable is not visible outside the block in which
it is defined. Recommend to use my variable as it is
faster than local.
• local
Local saves the value of a global variable. Here also
the variable is not accessible outside the block but it
is visible in the subroutine which is called from the
original block. You may need to use local when you
write code in Perl 4
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Danairat T.
Basic variable - Number
• Perl interpret both float and integer as 32 bits
according to the C compiler that compiled Perl
used.
Integer Literals
12
15
-2004
3485
1_000_000
Float Literals
1.25 # about 1 and a quarter
7.25e45 # 7.25 times 10 to the 45th power
-6.5e24 # negative 6.5 times 10 to the 24th
-12e-24 # negative 12 times 10 to the -24th
-1.2E-23 # another way to say that
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Danairat T.
Basic variable - Number
• To represent the non-decimal, we need to provide prefix for
Binary (0b), Octal (0), Hexadecimal (0x)
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
print 255, "n"; # decimal number
print 0b11111111, "n"; # 0 or 1
print 0377, "n"; # 0 to 7
print 0xFF, "n"; # 0 to F
exit(0);
NumberEx01.pl
35
Results:-
255
255
255
255

Danairat T.
Number Conversion
Convert BIN to DEC
• $number = 0b10110110;
Convert OCT to DEC
• $dec = 033653337357;
• $dec = oct("33653337357");
Convert HEX to DEC
• $dec = 0xDEADBEEF;
• $dec = hex("DEADBEEF");
Convert DEC to BIN
• $bin = sprintf("%b", 3735928559);
Convert DEC to OCT
• $oct = sprintf("%o", 3735928559);
Convert DEC to HEX
• $hex = sprintf("%X", 3735928559); # upper case A-F
• $hex = sprintf("%x", 3735928559); # lower case a-f
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Danairat T.
Operators Precedence
Associativity Operator
Left The "list" operators (leftward) eg. print(), sort(),
Left -> (method call, dereference)
Nonassociative ++++++++ -------- (autoincrement, autodecrement)
Right ******** (exponentiation)
Left =~=~=~=~ !~!~!~!~ (matches, doesn't match)
Left **** //// %%%% xxxx (multiply, divide, modulus, string replicate)
Left ++++ ---- .... (add, subtract, string concatenate)
Left << >>
Nonassociative Named unary operators (like chomp)
Nonassociative < > <= >= lt gt le ge
Nonassociative == != <=> eq ne cmp
Left & (bit-and)
Left | ^ (bit-or, bit-xor)
Nonassociative .. ... (noninclusive and inclusive range)
Right ?: (if-then-else)
Right = += -= *=, etc. (assignment and binary-assignment)
Left , => (comma and comma-arrow)
Nonassociative List operators (rightward)
Right not (logical not)
Left and (logical and)
Left or xor (logical or, logical xor)
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Danairat T.
Operators
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
print 2 + 118 . "n";
print 3 + 2 * 15 . "n";
print(3 + 2) * 15; # list operator impact to print()
print "n";
print((3 + 2) * 15);
print "n";
print 2**4 . ", " . -2**4 . "n";
print (2**4 . ", " . (-2)**4 . "n");
exit(0);
Results:-
120
33
5
75
16, -16
16,16
OperatorEx01.pl
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Danairat T.
Repetition Operators
• The string repetition operator (x) does to a left operand string.
The number 5 is converted to the string "5". This new string is
then copied four times as 5555
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
print ((3+2) x 4);
exit(0);
RepetitionEx01.pl
39
Results:-
5555

Danairat T.
Comparison Operators
• Perl always requires you to specify the proper type of
comparison, whether it be numeric or string.
Remarks: 7 is less than 30, but the string "30" comes before the string "7" (because the
ASCII value for 3 is less than the value for 7)
Comparison Numeric String
Equal == eq
Not equal != ne
Less than < lt
Greater than > gt
Less than or equal to <= le
Greater than or equal to >= ge
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Danairat T.
Comparison Operators
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
print 15==15; # true
print "n";
print 15==20; # false
print "n";
print 100 < 5; # false
print "n";
print 100 lt 5; # true
exit (0);
CompareEx01.pl
41
Results:-
1
1

Danairat T.
String Operator
• Built-in Auto Converting Strings into Numbers
• Examples:-
#!/usr/bin/perl
use strict;
use warnings;
# define a numeric string
my $scalar = '123.4e5';
# evaluate it in original string context
print $scalar; # produces '123.4e5'
print "n";
# evaluate it in numeric context
print $scalar + 1; # produces '12340001'
print "n";
exit(0);
AutoConvertEx01.pl
42
Results:-
123.4e5
12340001

Danairat T.
String Operator
• Converting Strings into Array using Split unary operator
• Examples:-
#!/usr/bin/perl
use strict; use warnings;
$csv = "one , two , three , four , five , six";
@list1 = split(', ' , $csv); # function style
print @list1;
print "n";
@list2 = split /, /, $csv; # regular expression style
print @list2;
print "n";
@list3 = split /s*, s*/, $csv; # regular expression style with trim the delimiter
print @list3;
print "n";
exit(0);
Results:-
one two three four five six
one two three four five six
onetwothreefourfivesix
SplitStringEx01.pl
43

Danairat T.
Perl Array
• A dynamic storage for a list which can be
grown, shrunk, alter. The array variable starts
prefix with an at-sign @
44
@numberArray = (1, 2, 3, 4, 5, 6);
@stringArray = ('one', 'two', 'three', 'four', 'five');
@myArray = ('one', 'two', 'three', 4, 'five');
@stringArray = qw(one two three four five);
@stringArray = qw(
one
two
three
four
five
);

Danairat T.
Perl Array - Examples
• Assign values to array and loop display value from array
45
#!/usr/bin/perl
use strict;
use warnings;
my @array = (); # initialize an array
$array[0] = "1st ";
$array[4] = "5th ";
@array[1..3, 5, -1] = ("2nd ", "3rd ", "4th ", "6th ", "Last");
foreach my $theRest (@array ) {
print $theRest;
}
exit(0);
ManipulateArrayEx01.pl
Results:-
1st 2nd 3rd 4th 5th Last

Danairat T.
• Using scalar to get arrays size and last position of an array $#
46
#!/usr/bin/perl
use strict;
use warnings;
my @myArray = ('one', 'two', 'three', 4, 'five');
my $arraySize = scalar(@myArray);
print "The Array size is: " . $arraySize . "n";
print "The last element is: " . $myArray[$#myArray] . "n";
exit(0);
ArraySizeEx01.pl
Results:-
The Array size is: 5
The last element is: five

Danairat T.
• Adding element to array using push
47
#!/usr/bin/perl
use strict;
use warnings;
$myArray[scalar(@myArray)] = ‘six’; # adding the new element;
push (@myArray, ’seven’);
print "The Array size is: " . scalar(@myArray) . "n";
exit(0);
AddingArrayEx01.pl
Results:-
The last element is: seven

Danairat T.
• Removing last elements from an Array using pop
48
#!/usr/bin/perl
use strict;
use warnings;
my @array = (1, 2, 3, 4, 5, 6);
push (@array, '7');
print "@arrayn";
my $last = pop @array;
print "$lastn"; # print 7
print "@arrayn";
exit(0);
PopArrayEx01.pl
Results:-
1 2 3 4 5 6 7
7
1 2 3 4 5 6

Danairat T.
• Adding element to array at position zero using unshift
• The below is equivalent to: splice @array, 0, 0, @more;
49
#!/usr/bin/perl
use strict;
use warnings;
unshift (@myArray, 'first_added', 'second_added'); # adding element at first
print "The Array size is: " . scalar(@myArray) . "n";
print "The array element values are: @myArray n";
exit(0);
UnshiftArrayEx01.pl
Results:-
The last element is: five
The array element values are: first_added second_added one two three 4 five

Danairat T.
• Removing first elements from an Array using shift
50
#!/usr/bin/perl
use strict;
use warnings;
my @array = (1, 2, 3, 4, 5, 6);
print "The starting array is @arrayn"; # array is now (1, 2, 3, 4, 5, 6, 7)
unshift (@array, -1, 0);
print "Array after unshift is @arrayn"; # array is now (-1, 0, 1, 2, 3, 4, 5, 6)
my $shiftValue = shift @array; # remove the first element of the array
print "shiftValue is: " . $shiftValue . "n";
$shiftValue = shift @array; # remove the first element of the array
print "shiftValue is: " . $shiftValue . "n";
print "The rest elements are: @arrayn";
exit(0);
ShiftArrayEx01.pl
Results:-
The starting array is 1 2 3 4 5 6
Array after unshift is -1 0 1 2 3 4 5 6
shiftValue is: -1
shiftValue is: 0
The rest elements are: 1 2 3 4 5 6

Danairat T.
• Flexible copy an array
51
#!/usr/bin/perl
use strict;
use warnings;
my $firstPosition; my @myArray2 = (); my @myArray3 = ();
($firstPosition, @myArray2[0..1], @myArray3) = @myArray;
print $firstPosition . "n"; # print the first element
foreach my $theRest (@myArray2) {
print $theRest . "n"; # print element from myArray2
}
exit(0);
CopyArrayEx01.pl
Results:-
one
two
three

Danairat T.
• Resizing and Truncating an Array. The below is fastest way to
resize an array.
52
#!/usr/bin/perl
use strict;
use warnings;
my @myArray = ("apple ", "banana ", "orange ");
print "Array size is: ". scalar(@myArray) . "n";
$#myArray = 99; # increase an array size to 100 without assign value
$#myArray = 1; # decrease an array size to 2
print "Array element values are: @myArray n";
exit(0);
ResizeArrayEx01.pl
Results:-
Array size is: 3
Array size is: 100
Array size is: 2
Array element values are: apple banana

Danairat T.
• Remove all elements
53
#!/usr/bin/perl
use strict;
use warnings;
my @myArray = ("apple ", "banana ", "orange ");
@myArray = (); # remove all elements and return memory to OS
exit(0);
RemoveAllElementsArrayEx02.pl
Results:-
Array size is: 3
Array size is: 0

Danairat T.
• Sorting Arrays using sort
54
#!/usr/bin/perl
use strict;
use warnings;
my @words = ('here', 'are', 'some', 'words');
my @alphabetical = sort @words;
print "The starting array: @words n";
print "The sorted array: @alphabetical n";
exit(0);
SortArrayEx02.pl
Results:-
The starting array: here are some words
The sorted array: are here some words

Danairat T.
• Reversing Arrays using reverse. This is only to reverse an array
but not to do reverse-sort array.
55
#!/usr/bin/perl
use strict;
use warnings;
my @alphabetical = reverse @words;
print "The reversed array: @alphabetical n";
exit(0);
ReverseArrayEx02.pl
Results:-
The sorted array: words some are here

Danairat T.
• Reversing Sort Arrays using sort
56
#!/usr/bin/perl
use strict;
use warnings;
my @alphabetical = sort {$b cmp $a} @words;
print "The reversed sort array: @alphabetical n";
exit(0);
ReverseArrayEx02.pl
Results:-
The reversed sorted array: words some here are

Danairat T.
• Numbering sort using {$a <=> $b}. The built-in global variables
$a and $b for sorting algorithms
57
#!/usr/bin/perl
use strict;
use warnings;
my @words = ('100', '5', '2000', '9');
my @sortArray = sort {$a <=> $b} @words;
print "The sorted array: @sortArray n";
exit(0);
NumberSortedArrayEx02.pl
Results:-
The starting array: 100 5 2000 9
The sorted array: 5 9 100 2000

Danairat T.
• Alphanumeric (mixed) sort using {int($a) <=> int($b) or $a cmp $b}. The
<=> is for number and cmp is for character comparison.
58
#!/usr/bin/perl
use strict;
use warnings;
my @words = ("1000", "zebra", "100", "apple", "5", "2000", "9");
my @sortArray = sort {int($a) <=> int($b) or $a cmp $b} @words;
print "The sort array: @sortArray n";
exit(0);
AlphaSortedArrayEx02.pl
Results:-
Argument "zebra" isn't numeric in int at test.pl line 6.
Argument "apple" isn't numeric in int at test.pl line 6.
The starting array: 1000 zebra 100 apple 5 2000 9
The sort array: apple zebra 5 9 100 1000 2000

Danairat T.
• Converting array into scalar using join
59
#!/usr/bin/perl
use strict;
use warnings;
my @words = ("1000", "zebra", "100", "apple", "5", "2000", "9");
@words = sort {int($a) <=> int($b) or $a cmp $b} @words;
print "The sorted array: @words n";
my $scalarWords = join ("|", @words);
print "The result is: $scalarWords n";
exit(0);
SalarFromArrayEx02.pl
Results:-
The starting array: 1000 zebra 100 apple 5 2000 9
Argument "zebra" isn't numeric in int at test.pl line 7.
Argument "apple" isn't numeric in int at test.pl line 7.
The sorted array: apple zebra 5 9 100 1000 2000
The result is: apple|zebra|5|9|100|1000|2000

Danairat T.
• Converting scalar to array using split
60
#!/usr/bin/perl
use strict;
use warnings;
my $words = "apple|zebra|5|9|100|1000|2000";
my @wordsArray = split (/|/, $words);
print "The result is: @wordsArray n";
exit(0);
ArrayFromSplitEx02.pl
Results:-
The result is: apple zebra 5 9 100 1000 2000

Danairat T.
• Replace and insert elements in array using splice
splice @array, $from, $quantity, @replacement;
61
#!/usr/bin/perl
use strict;
use warnings;
my @array = ('a', 'b', 'c', 'd', 'e', 'f');
# replace third element with three new elements
my $removed = splice @array, 2, 1, (1, 2, 3);
print "The array values are: @array n";
print "The removed element is: $removed n";
exit(0);
ReplaceInsertArrayEx01.pl
Results:-
The array values are: a b 1 2 3 d e f
The removed element is: c

Danairat T.
• Remove elements in array using splice
splice @array, $from, $quantity;
62
#!/usr/bin/perl
use strict;
use warnings;
my @array = ('a', 'b', 'c', 'd', 'e', 'f');
# remove elements 2, 3 and 4
my @removed = splice @array, 2, 3; # start from position#2 for 3 positions
print "The rest elements are: @arrayn";
print "The removed elements are: @removedn";
exit(0);
RemoveElementsArrayEx01.pl
Results:-
The rest elements are: a b f
The removed elements are: c d e

Danairat T.
• Remove elements to the end of the array using splice
splice @array, $quantity;
63
#!/usr/bin/perl
use strict;
use warnings;
my @array = ('a', 'b', 'c', 'd', 'e', 'f');
# remove last three elements
my @last_4_elements = splice @array, -4; # start from last pos of 4 to the end
print "@arrayn";
print "@last_4_elementsn";
exit(0);
RemoveElementsArrayEx02.pl
Results:-
a b
c d e f

Danairat T.
Date and Time
• The epoch
The epoch system, as used most operating systems, represents a datetime
as the number of seconds after a specific date and time. For Unix systems,
the epoch began on January 1, 1970 at midnight GMT (UTC).
time()
• Local time
The local time is UTC plus the local time zone offset. While UTC is great for
internal use, most people want to see datetimes in terms of their location.
localtime()
64

Danairat T.
Date and Time
• Example:-
65
#!/usr/bin/perl
use strict;
use warnings;
my $myEpoch = time(); # time in second that counting from 1 Jan 1970
print $myEpoch . "n";
my $myDatetime = localtime($myEpoch); # auto convert to scalar
print $myDatetime . "n";
exit(0);
DateAndTimeEx01.pl
Results:-
1258345951
Mon Nov 16 11:32:31 2009

Danairat T.
Date and Time
• The Local Time
The Local Time can be return value in scalar or in array and
provide you to get the value in day, month, year, hh, mm, etc.
66
$sec - seconds [0-60, to allow for leap seconds]
$min - minutes [0-59],
$hour - hours [0-23],
$mday - day of the month [1-31] (Note: from '1'),
$mon - month [0-11] (Jan. is '0'),
$year - number of years since 1900 (1999 is 99; 2000 is 100),
$wday - day of the week [0-6] (Sun. is '0'),
$yday - day of the year [0-365] (total of 366 possible for leap year)
$isdst - daylight savings time [0,1] -- returns boolean '0' or '1' if Daylight Savings active.
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time());

Danairat T.
Date and Time
• Example:-
67
#!/usr/bin/perl
use strict;
use warnings;
my $myEpoch = time(); # time counting from 1 Jan 1970
print $myEpoch . "n";
my $myDatetime = localtime($myEpoch); # auto convert to scalar
print $myDatetime . "n";
my @myTimeData = localtime($myEpoch); # same as localtime() but use the fixed value from previous var
print join (" ", @myTimeData) . "n";
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = @myTimeData;
printf "%4d-%02d-%02d %02d:%02d:%02dn", $year+1900,$mon+1,$mday,$hour,$min,$sec;
exit(0);
LocalTimeEx01.pl
Results:-
1258346693
Mon Nov 16 11:44:53 2009
53 44 11 16 10 109 1 319 0
2009-11-16 11:44:53

Danairat T.
Date and Time
• Date/Time calculation can be done by using the epoch time
68
use Time::Local;
my $time = timelocal($sec,$min,$hours,$day,$month,$year);
# replace 'timelocal' with 'timegm' if your input date is GMT/UTC

Danairat T.
Date and Time
• Date/Time calculation can be done by using the epoch time
69
#!/usr/bin/perl
use strict;
use warnings;
use Time::Local;
my $myCurrentTimeEpoch = time(); # time counting from 1 Jan 1970
my $myCurrentDatetime = localtime($myCurrentTimeEpoch); # auto convert to scalar
print "myCurrentTimeEpoch is: " . $myCurrentTimeEpoch . "n";
print "myCurrentDatetime is: " . $myCurrentDatetime . "n";
my $myTimeEpoch = timelocal(0,0,0,14,10,109); # 14-Nov-2009 14:30
print "myTimeEpoch is: " . $myTimeEpoch . "n";
my $myDiffTime = $myCurrentTimeEpoch - $myTimeEpoch;
print '$myCurrentTimeEpoch - $myTimeEpoch =' . $myDiffTime . "n";
my $myDiffDay = int($myDiffTime / (3600 * 24));
print "myDiffDay is: " . $myDiffDay . "n";
exit(0);
DateTimeCalcEx01.pl
Results:-
myCurrentTimeEpoch is: 1258356343
myCurrentDatetime is: Mon Nov 16 14:25:43 2009
myTimeEpoch is: 1258131600
$myCurrentTimeEpoch - $myTimeEpoch =224743
myDiffDay is: 2

Danairat T.
Perl Hash
• A compound data type as in key value pairs.
• Hash has no ‘first’ or ‘last’ element like in an array.
• Hashes consist of paired values, Perl provides the =>
operator as an alternative to the comma.
my %myHash = (Mouse => 'Jerry', Cat => 'Tom', Dog => 'Spike');
– Hash variable use % as a represent sign.
– Hash values can be any scalar.
– Hash keys can only be strings. The => operator also allows us to omit the
quotes by treating its left-hand side as a constant string.
70

Danairat T.
Perl Hash- Examples
• Add, modify and display Hash table
• Basic Hash Examples:-
71
#!/usr/bin/perl
use strict;
use warnings;
my %myHash = (Mouse => 'Jerry', Cat => 'Tom');
$myHash{'Dog'} = 'Spike';
@myHash{'Bird', 'Fish'} = ('Tweet', 'Nemo'); # it is @hash{@keys} = @values;
$myHash{'Dog'} = 'Bark';
foreach my $myKey (sort keys %myHash) {
print "$myKey => $myHash{$myKey} n";
}
exit(0);
HashEx01.pl
Results:-
Bird => Tweet
Cat => Tom
Dog => Bark
Fish => Nemo
Mouse => Jerry

Danairat T.
Perl Hash- Examples
• Hash keys and values
72
#!/usr/bin/perl
use strict;
use warnings;
# define a default set of hash keys and values
my %myHash = (Cat => 'Tom', Mouse => 'Jerry');
my @myKeys = keys %myHash;
my @myValues = values %myHash;
print “Keys are: @myKeys”;
print “Values are: @myValues”;
exit(0);
HashKeysValuesEx01.pl
Results:-
Keys are: Mouse Cat
Values are: Jerry Tom

Danairat T.
Perl Hash- Examples
• Removing Hash Keys and Values
73
#!/usr/bin/perl
use strict;
use warnings;
my %myHash = ();
%myHash = (Mouse => 'Jerry', Cat => 'Tom');
print "01 Starting result: " . $myHash{'Cat'} . "n";
undef $myHash{'Cat'};
if (defined $myHash{'Cat'}) {
print "02 Key is still defined: " . $myHash{'Cat'} . "n"; # error complain here
}
if (exists $myHash{'Cat'}) {
print "03 Key is still exist: " . $myHash{'Cat'} . "n"; # no error but no value
}
delete $myHash{'Cat'};
if (exists $myHash{'Cat'}) {
print "04 Delete result:" . $myHash{'Cat'} . "n";
} exit(0);
HashRemoveValueEx01.pl
Results:-
01 Starting result: Tom
Use of uninitialized value in concatenation
(.) or string at test.pl line 14.
03 Key is still exist:

Danairat T.
Perl Hash- Examples
• Combine hashes
• Basic Hash Examples:-
74
#!/usr/bin/perl
use strict;
use warnings;
my %default_animals = (Cat => 'Tom', Mouse => 'Jerry');
# get another set of keys and values
my %input_animals = (Cat => 'Ginger', Mouse => 'Jerry');
# combining keys and values with overrides
my %animals = (%default_animals, %input_animals);
print "$animals{Cat}n"; # prints 'Ginger'
exit(0);
HashCombineEx01.pl
Results:-
Ginger

Danairat T.
Perl Hash- Examples
• Converting Hash into Array using simply =
75
#!/usr/bin/perl
use strict;
use warnings;
foreach my $myKey (keys %myHash) {
print "$myKey with value $myHash{$myKey} n";
}
my @myArray = %myHash;
foreach my $myElement (@myArray) {
print "myElement is $myElement n";
}
exit(0);
ArrayFromHashEx01.pl
Results:-
Mouse with value Jerry
Cat with value Tom
myElement is Mouse
myElement is Jerry
myElement is Cat
myElement is Tom

Danairat T.
Perl Hash- Examples
• Converting hash into array when the hash contain undef value
76
#!/usr/bin/perl
use strict;
use warnings;
foreach my $myKey (keys %myHash) {
print "$myKey with value $myHash{$myKey} n";
}
undef $myHash{'Mouse'};
my @myArray = %myHash;
foreach my $myElement (@myArray) {
print "myElement is $myElement n";
}
exit(0);
ArrayFromHashEx02.pl
Results:-
Cat with value Tom
myElement is Mouse
Use of uninitialized value in concatenation
(.) or string at example.pl line 15.
myElement is
myElement is Cat
myElement is Tom

Danairat T.
Perl Hash- Examples
• Named Arguments for Hash passing to Subroutines
• Perl have no built-in %_ variable. You need to use @_
77
#!/usr/bin/perl
use strict;
use warnings;
sub hashProcess {
my %mySubHash = @_;
foreach my $myKey (keys % mySubHash) {
print "$myKey with value $ mySubHash{$myKey} n";
}
}
exit(0);
HashPassingEx01.pl
Results:-
Cat with value Tom

Danairat T.
Flow Control and Loop
• Block
• If, elsif, else
• Unless
• While
• For
• For each
• Do.. until
78

Danairat T.
• Program Blocks is construct that allows several statements
within in curly braces. The block also defines a new scope in
which variables can be declared and used
{
STATEMENT;
STATEMENT;
... ;
STATEMENT;
}
79

Danairat T.
• A bare block Example:-
80
use strict;
use warnings;
my $myString = "Hi";
{
my $myString = "Hello";
print "myString inside the block is $myString n";
}
print "myString outside the block is $myString n";
exit(0);
BlockEx01.pl
Results:-
myString inside the block is Hello
myString outside the block is Hi

Danairat T.
• The Special block: BEGIN, INIT, END. Perl will perform BEGIN then INIT then
END block.
81
#!/usr/bin/perl
use strict;
use warnings;
END {
print "Ending... n";
}
print "No Block Code Here... n";
INIT {
print "Initializing...n";
}
BEGIN {
print "Beginning.. n";
}
exit(0);
SpecialBlockEx01.pl
Results:-
Beginning..
Initializing...
No Block Code Here...
Ending...

Danairat T.
• 'if‘ : The condition logic, basic form:-
if (EXPRESSION) BLOCK
• Invert the syntax of an if statement put the BLOCK first.
BLOCK if EXPRESSION;
STATEMENT if EXPRESSION;
• In this case we can both omit the parentheses of the condition and also
replace the block with a bare statement
82

Danairat T.
If, then, and else conditions are implemented with the else keyword:
if (EXPRESSION) BLOCK else BLOCK
83
if ($greet1 eq “Hello”) {
if ($greet2 eq “HI”) {
print "true n";
} else {
print "false n";
}
} else {
print “No Greetingn";
}
1st if
1st else
2nd if
2nd else

Danairat T.
• elsif for multiple conditions chains.
if (EXPRESSION) BLOCK elsif (EXPRESSION) BLOCK elsif...
if (EXPRESSION) BLOCK elsif (EXPRESSION) BLOCK else BLOCK
84
The equivalent code using elsif
is simpler:
if ($a eq $b) {
print "Equal";
} elsif ($a gt $b) {
print "Greater";
} else {
print "Less";
}
For example, to compare strings
using just if and else we might
write:
if ($a eq $b) {
print "Equal";
} else {
if ($a gt $b) {
print "Greater";
} else {
print "Less";
}
}

Danairat T.
• unless (“if not”): The unless is very useful to check the
conditions and return (or exit program) if the conditions did
not match with expectation.
Below is the same result but “unless” make the code simpler.
85
if (not open FILE, $filename) {
return "Failed to open $filename";
}
return "Failed to open $filename"
unless (open FILE, $filename);

Danairat T.
• The Ternary Operator works as an expression and returns a value that
can be assigned in other expressions.
expression1 ? expression2 : expression3
86
#!/usr/bin/perl
use strict;
use warnings;
my $check = “exist”;
my $customerStatus = (if $check eq "exist") ? "Existing" : "New";
print “$customerStatus n";
exit(0);
TernaryEx01.pl
Results:-
Existing

Danairat T.
Switches: the block contains a multiple-branch condition.
SWITCH: label prefixes the block to indicate that
87
#!/usr/bin/perl
use strict;
use warnings;
print<<EOT;
select on of:-
1. Menu1
2. Menu2
3. Menu3
EOT
print "Please enter choice 1, 2 or 3 :";
my $input = <STDIN>;
chomp($input);
switch: {
$input eq '1' and do { printLabel($input); last; };
}
sub printLabel {
my ($label, @others) = @_;
print "label is: " . $label . "n";
}
exit(0);
SwitchEx01.pl
Results:-
select on of:-
1. Menu1
2. Menu2
3. Menu3
Please enter choice 1, 2 or 3 :3
label is: 3

Danairat T.
Loops
The block of code that is executed repeatedly, according to
the criteria of the loop's controlling conditions.
Both kinds of loop can be controlled using statements using next, last.
88
- Iterating loops, provided by for and foreach
- Conditional loops, provided by while and until.

Danairat T.
For loop and Foreach loop
89
foreach (@array) {
print "$_ n";
}
foreach my $element (@array) {
print $element,"n";
}
for ($n = 0; $n < $#array; $n ++) {
print $array [$n], "n";
}
or

Danairat T.
while, until, and do loop
The conditional Loops to execute the loop for so long as the
condition holds.
90
#!/usr/bin/perl
use warnings;
use strict;
my $n = 0;
while ($n++ < 10) {
print $n . "n";
}
WhileEx01.pl
Results:-
1
2
3
4
5
6
7
8
9
10

Danairat T.
do...while and do...until
The loop can ensure that the body is executed at least once.
91
#!/usr/bin/perl
use warnings;
use strict;
my $input;
do {
$input = <STDIN>;
print "You typed: $input n";
} while ($input !~ /^quit/);
exit(0);
#!/usr/bin/perl
use warnings;
use strict;
my $input;
do {
$input = <STDIN>;
print "You typed: $input n";
} until ($input =~ /^quit/);
exit(0);

Danairat T.
Controlling Loop Execution
next, which go to the next iteration (testing the loop condition),
last, which immediately exits the loop
redo, which restarts the current iteration (without retesting the loop condition).
92
#!/usr/bin/perl
use warnings;
use strict;
# define a selection of strings one of which is 'start'
my @lines = ("this", "that", "the other", "start", "the data", "we want");
# discard lines until we see the 'start' marker
while (my $line = shift @lines) {
last if $line eq 'start';
}
# print out the remaining elements using interpolation ($")
print "@lines";
exit (0);
WhileWithShiftEx01.pl
Results:-
the data we want

Danairat T.
map
map EXPRESSION, LIST
map BLOCK LIST
• Map is to convert the elements of a list one by one, and produce a new list
as a result.
• The expression or block performs the conversion, so map is conceptually
related to a foreach loop. functions perform aliasing $_
93

Danairat T.
map
94
#!/usr/bin/perl
use warnings;
use strict;
my @myNames = ('jacob', 'alexander', 'ethan', 'andrew');
my @ucNames = map(ucfirst($_), @myNames);
print "@ucNames" . "n";
exit(0);
MapEx01.pl
Results:-
Jacob Alexander Ethan Andrew

Danairat T.
grep
grep EXPRESSION, LIST
grep BLOCK LIST
• grep is to return a list containing a subset of the original list.
• The expression or block is evaluated to a True or False value to see if the
element is eligible for inclusion, so grep is conceptually related to a while
loop. functions perform aliasing $_
95

Danairat T.
grep
96
#!/usr/bin/perl
use warnings;
use strict;
my @myNames = ('Jacob', 'Michael', 'Joshua', 'Matthew', 'Alexander', 'Andrew');
my @grepNames = grep(/^A/, @myNames);
print "@grepNames" . "n";
exit(0);
GrepEx01.pl
Results:-
Alexander Andrew

Danairat T.
Line ID: Danairat
+668-1559-1446
Thank you

Perl Programming - 01 Basic Perl

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