Telecom Tutorials by Samir Amberkar

Index	1) Books 2) Enforce variable declaration etc. 3) Variable declaration 4) Declare or define a HASH array 5) Declare or define a plain array 6) Getting arguments to script 7) Environment variables 8) File operations - open, close 9) Pattern matching 10) Replacing pattern Globally and Ignoring case 11) Access array element 12) Access hash array element 13) In loop 14) Sorting alphabetically 15) Sorting numerically 16) Get (and remove) 1st element of an array 17) Get (and remove) last element of an array 18) Add an element at the beginning of an array UNSHIFT/SHIFT work like queue (FIFO)operations 19) Add an element at the end of an array. PUSH/POP works like stack (LIFO) operations 20) Pointers 21) Array size 22) Delete a key from hash array 23) All values of hash 24) Check if file exists 25) Get filesize 26) Check whether directory 27) Reading directory recursively 28) Rename the file 29) Deleting file 30) Copying file 31) Write into file 32) Append file 33) Executing system command 34) Functions 35) Array of array 36) Hash of array 37) Array of hash 38) Hash of hash 39) Reading complete file as one string 40) Using CGI module 41) Sending mail using Net::SMTP 42) Using Win32 module for MS Excelsheet 43) Using Windows Semaphore 44) Using CGI module for upload HTML form element for upload: "<input type=file name=attachment>" 45) Modifier for regular expressions 46) Wildcards 47) Repetitions 48) Regularly used functions, operators Core programmers will always use Perl scripts to automate their manual work. Problem is recalling some of common functions, coding tricks. This tutorial notes down these regularly used lines of Perl code.
1) Books	Best book to start is the one written by none other than by Perl's authors,      Programming Perl by Larry Wall et al
2) Enforce variable declaration etc.	use strict;
3) Variable declaration	my $variable = 0;
4) Declare or define a HASH array	my %hash_array = ( "KEY" => "VALUE", 'Key' => 'Value' );
5) Declare or define a plain array	my @array = ( 'ELEMENT', 'Element' );
6) Getting arguments to script	my $argument1 = $ARGV[0]; die "Argument 1 not passed\n" unless( $argument1 );
7) Environment variables	my $env1 = $ENV{'ENV1'};
8) File operations - open, close	open( FILE, $input_file ) or die "Can not open $input_file: $!\n"; while( <FILE> ) { chomp; } close( FILE );
9) Pattern matching	if( $variable =~ m/pattern/) { print "Pattern matched\n"; }
10) Replacing pattern Globally and Ignoring case	my $pattern_replace_ctr = ($variable =~ s/pattern/replacewith/gi);
11) Access array element	print $plain_array[0];
12) Access hash array element	print $hash_array{ 'KEY' };
13) In loop	foreach my $element (@plain_array) { $element = 'new element'; } foreach my $key (keys %hash_array) { $hash_array{ $key } = 'new value'; }
14) Sorting alphabetically	my @sorted_array = sort @plain_array;
15) Sorting numerically	my @sorted_keys = sort { $a <=> $b } keys %hash_array;
16) Get (and remove) 1st element of an array	shift( @array );
17) Get (and remove) last element of an array	pop( @array );
18) Add an element at the beginning of an array UNSHIFT/SHIFT work like queue (FIFO)operations	unshift( @array, $element );
19) Add an element at the end of an array. PUSH/POP works like stack (LIFO) operations	push( @array, $element );
20) Pointers	$ptr2var = $var; $$ptr2var = 'new var value' ; $ptr2array = @array; $$ptr2array[0] = 'new 0th element of array'; #Or $ptr2array->[0] = 'new 0th element of array'; $ptr2hash = %hash_array; $$ptr2hash{ KEY } = 'new value for KEY'; #Or $ptr2hash->{ KEY } = 'new value for KEY';
21) Array size	my $array_size = $#array; #Or my $array_size = SCALAR( @array );
22) Delete a key from hash array	delete $hash_array{ 'KEY' };
23) All values of hash	@values = values %hash_array;
24) Check if file exists	if ( -e $filename ) { print "File $filename exists.\n"; }
25) Get filesize	my $filesize = -s $filename;
26) Check whether directory	if( -d $filename ) { print "$filename is directory.\n"; }
27) Reading directory recursively	my @files = ($root_dir); while( @files ) { my $file = pop( @files ); if( -d $file ) { opendir( DIR, $file ) or next; my $t_file; while( $t_file = readdir( DIR ) ) { next if( $t_file =~ /^\.$/ ); next if( $t_file =~ /^\.\.$/ ); push( @files, "$file/$t_file" ); } closedir( DIR ); next; } print "File $file ok.\n"; }
28) Rename the file	rename( $filename, $new_filename );
29) Deleting file	unlink( $filename );
30) Copying file	use File::Copy; copy( $filename, $copy_of_filename );
31) Write into file	open( OUT_FILE, "> $filename" ) or die "Can not open out file $filename: $!\n"; print OUT_FILE "Test line 1\n"; close( OUT_FILE );
32) Append file	open( OUT_FILE, ">> $filename" ) or die "Can not open out file $filename: $!\n"; print OUT_FILE "Test line 2\n"; close( OUT_FILE );
33) Executing system command	system( $command );
34) Functions	sub test_function { my ($param1, $param2) = @_; my ($out1, $out2); return ($out1, $out2); }
35) Array of array	my @array_of_array = ( [ "1 of 1", "2 of 1"], [ "1 of 2", "2 of 2"] ); $array_of_array[0][0] = "New 1 of 1"; $array_of_array[0][1] = "New 2 of 1"; print join( "\n", @{ $array_of_array[0] } )."\n";
36) Hash of array	my %hash_of_array = ( 'KEY1' => [ '1 of KEY1', '2 of KEY1' ], 'KEY2' => [ '1 of KEY2', '2 of KEY2' ] ); $hash_of_array{ 'KEY1' }[0] = 'New 1 of KEY1'; $hash_of_array{ 'KEY1' }[1] = 'New 2 of KEY1'; print join( "\n", @{ $hash_of_array{ 'KEY1' } } )."\n";
37) Array of hash	my @array_of_hash = ( { 'KEY1 of 1st Array' => 'Value of KEY1 of 1st Array', 'KEY2 of 1st Array' => 'Value of KEY2 of 1st Array' }, { 'KEY1 of 2nd Array' => 'Value of KEY1 of 2nd Array', 'KEY2 of 2nd Array' => 'Value of KEY2 of 2nd Array' } ); $array_of_hash[0]{'KEY1 of 1st Array'} = 'New value of KEY1 of 1st Array'; $array_of_hash[0]{'KEY2 of 1st Array'} = 'New value of KEY2 of 1st Array'; print join( "\n", sort keys %{ $array_of_hash[0] } )."\n"; print join( "\n", sort values %{ $array_of_hash[0] } )."\n";
38) Hash of hash	my %hash_of_hash = ( 'HASH1' => { 'KEY1 of HASH1' => 'Value of KEY1 of HASH1', 'KEY2 of HASH1' => 'Value of KEY2 of HASH1', }, 'HASH2' => { 'KEY1 of HASH2' => 'Value of KEY1 of HASH2', 'KEY2 of HASH2' => 'Value of KEY2 of HASH2', } ); $hash_of_hash{ 'HASH1' }{ 'KEY1 of HASH1' } = 'New value of KEY1 of HASH1'; $hash_of_hash{ 'HASH1' }{ 'KEY2 of HASH1' } = 'New value of KEY2 of HASH1'; print join( "\n", sort keys %{ $hash_of_hash{ 'HASH1' } } )."\n"; print join( "\n", sort values %{ $hash_of_hash{ 'HASH1' } } )."\n";
39) Reading complete file as one string	my $filename = $0; #Name of current script flle my $rem_separater = $/; undef $/; open( FILE, $filename ) or die "Can not open $filename: $!\n"; my $complete_file = <FILE>; close( FILE ); $/ = $rem_separater; print $complete_file;
40) Using CGI module	use CGI; my $query = new CGI; print "Content-type: text/html\n\n"; print $query->param( 'Textbox1' );
41) Sending mail using Net::SMTP	use Net::SMTP; my $smtp = Net::SMTP->new( $server ); die "SMTP not responding: $!\n" unless( $smtp ); $smtp->mail( $sender_id ); $smtp->to( $email_id ); $smtp->data(); $smtp->datasend("To: $email_id\n"); $smtp->datasend("From: $sender_id\n"); $smtp->datasend("Subject: $subject\n"); $smtp->datasend("\n"); $smtp->datasend("$body\n"); $smtp->dataend(); $smtp->quit;
42) Using Win32 module for MS Excelsheet	use Win32::OLE qw(in with); use Win32::OLE::Const 'Microsoft Excel'; use Win32::OLE::Variant; use Win32::OLE::NLS qw(:LOCALE :DATE); $Win32::OLE::Warn = 3; # die on errors... my $Excel = Win32::OLE->GetActiveObject('Excel.Application') || Win32::OLE->new('Excel.Application', 'Quit'); my $report_xls = 'test.xls'; my $Book = $Excel->Workbooks->Open( $report_xls ); my $Sheet = $Book->Worksheets( 'Sheet1' ); my ($row,$col) = (2,5); $Sheet->Cells($row,$col)->{'Value'} = "Cell ($row,$col) value"; $Sheet->Cells($row,$col)->Font->{ColorIndex} = 3; $Sheet->Cells($row,$col)->Interior->{ColorIndex} = 5; $Sheet->Cells($row,$col)->{HorizontalAlignment} = xlHAlignLeft; $Sheet->Cells($row,$col)->{VerticalAlignment} = xlVAlignTop; $Sheet->Cells($row,$col)->Font->{Name} = "Courier"; $Book->Save(); $Book->Close();
43) Using Windows Semaphore	require Win32::Semaphore; my $sema_name = 'semaphore-test'; my $sema_initial = 1; my $sema_maximum = 1; my $sema_wait_limit = 60; #seconds my $semaphore = Win32::Semaphore->new($sema_initial,$sema_maximum,$sema_name); my $wait_ret = $semaphore->wait( 1000 * $sema_wait_limit );
44) Using CGI module for upload HTML form element for upload: "<input type=file name=attachment>"	use CGI; use CGI::Carp qw ( fatalsToBrowser ); use File::Basename; my $attachment_size_limit = 5; #MB my $max_post_size = 1024 * 1000 * $attachment_size_limit + 1024; #1024 for actual request CGI::upload_hook(\&upload_hook); my $query = new CGI; print "Content-type: text/html\n\n"; my $filename = $query->param('attachment'); if( $filename ) { my $upload_filehandle = $query->upload('attachment'); my ( $name, $path, $extension ) = fileparse ( $filename, '\..*' ); $filename = $name.$extension; $filename =~ s/[^\w|\-|\.]/_/g; open ( UPLOADATTACH, "> $local_filename" ) or exit; binmode UPLOADATTACH; while ( <$upload_filehandle> ) { print UPLOADATTACH; } close UPLOADATTACH; } sub upload_hook { my ($filename, $buffer, $bytes_read, $data) = @_; if( $bytes_read > $max_post_size ) { print 'Upload file size exceeds limit of '.$attachment_size_limit.' MB.<br><br>'; print 'Click <a href="#" onClick="history.go(-1)">here</a> to go back.<br><br>'; exit; } }
45) Modifier for regular expressions	g Match globally i Ignore case s '.' matches newline
46) Wildcards	. Match any character except newline unless /s modifier used \w Alphanumeric \W Non-alphanumeric \s Any white-space character (Space, Tab, Newline) \d Digit \D Non-digit \t Tab \n Newline \r Return \f Formfeed \a Alarm \e Escape \b Word boundary \B non-Word boundary
47) Repetitions	* Match 0 or more + 1 or more ? 0 or 1 but not more {n} Exactly n times {n,} At least n times {m,n} Least m, maximum n times
48) Regularly used functions, operators	** exponentiation hex(x) Covert decimal value of hexadecimal x int(x) interger portion of x log(x) log to the base e (natural) of x rand(n) random fraction between 0 to n

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