Introduktion til Perl-kommandoer
Perl er et programmeringssprog. Tidligere designet kun til tekstredigering, bruges det nu til mange formål som systemadministration i Linux, webudvikling, netværksprogrammering osv. Hovedarkitekten og skaberen af Perl er Larry Wall. Det blev oprettet tilbage i 1987 og bruges stadig som et stort programmeringssprog. Perl er et højt niveau sprog. Det er også et fortolket og dynamisk programmeringssprog. Nu lærer vi Perl-kommandoer i detaljer.
Grundlæggende Perl-kommandoer
1. Grundlæggende Perl-kommando, der skal udskrives i Perl
#!/usr/bin/perl
# This will print "Hello, World"
print "Hello, world\n";
2. Kommentar på en linje i Perl
#!/usr/bin/perl
# This is a single line comment
print "Hello Perl\n";
3. Kommentar med flere linjer i Perl
#!/usr/bin/perl
=begin comment
This is a multiline comment.
Line 1
Line 2
Line 3
We can insert
as much lines
as comments
until we code =cut
to end multiline comments
=cut
print "Hello Perl\n";
4. Variabel tildeling i Perl (Interpolation af dobbeltciterede variabler)
#!/usr/bin/perl
$a = 10;
print "Variable a = $a\n";
5. Undslippe karakter i Perl
#!/usr/bin/perl
$a = "This is \"Perl\"";
print "$a\n";
print "\$a\n";
6. I Perl har strenge forskellige adfærd med dobbelt citater og enkelt citater. Mens dobbeltnoteringer tillader interpolering, gør ikke enkelte citater det.
#!/usr/bin/perl
# Interpolation example.
$str = "Hello \nPerl";
print "$str\n";
# Non-interpolation example.
$str = 'Hello \nPerl';
print "$str\n";
7. Store bogstaver i Perl-kommandoen
#!/usr/bin/perl
# Only u will become upper case.
$str = "\uhello perl";
print "$str\n";
# All the letters will become Uppercase.
$str = "\Uhello perl";
print "$str\n";
# A portion of string will become Uppercase.
$str = "hello \Uperl\E";
print "$str\n";
8. Scalar Variabel tildeling i Perl
#!/usr/bin/perl
$age = 35; # Assigning an integer
$name = "Tony Stark"; # Assigning a string
$pi = 3.14; # Assigning a floating point
print "Age = $age\n";
print "Name = $name\n";
print "Pi = $pi\n";
9. Enkle skalære operationer i Perl
#!/usr/bin/perl
$constr = "hi" . "perl";# Concatenates two or more strings.
$add = 40 + 10; # addition of two numbers.
$prod = 4 * 51;# multiplication of two numbers.
$connumstr = $constr . $add;# concatenation of string and number.
print "str = $constr\n";
print "num = $add\n";
print "mul = $prod\n";
print "mix = $connumstr\n";
10. Special Literals in Perl
#!/usr/bin/perl
print "Current file name ". __FILENAME__ . "\n";
print "Current Line Number " . __LINENO__ ."\n";
print "Current Package " . __PACKAGENAME__ ."\n";
# here they cannot be interpolated
print "__FILENAME__ __LINENO__ __PACKAGENAME__\n";
Mellemliggende Perl-kommandoer
1. Arrays i Perl
Array-indeks starter fra 0. Det negative indeks angiver elementer fra den sidste position. Eksempel nedenfor.
#!/usr/bin/perl
@weekday = qw/Mon Tue Wed Thu Fri Sat Sun/;
print "$weekday(0)\n";
print "$weekday(1)\n";
print "$weekday(2)\n";
print "$weekday(6)\n";
print "$weekday(-1)\n";
print "$weekday(-6)\n";
2. Matriser for elementer i en rækkefølge
#!/usr/bin/perl
@oneToTen = (1..10);
@fiftyToSeventyfive = (50..75);
@aToZ = (a..z);
print "@oneToTen\n"; # Prints one to ten
print "@fiftyToSeventyfive\n"; # Prints fifty to seventy five
print "@aToZ\n"; # Prints from a to z
3. Tilføjelse og fjernelse af arrayelement
#!/usr/bin/perl
# creating an array
@expression = ("happy", "sad", "angry");
print "1. \@expression = @expression\n";
# add element to the end of the arraypush(@expression, "jolly");
print "2. \@expression = @expression\n";
# add element to the beginning of the arrayunshift(@expression, "excited");
print "3. \@expression = @expression\n";
# remove element to the last of the array.pop(@expression);
print "4. \@expression = @expression\n";
# remove element from the beginning of the array.shift(@expression);
print "5. \@expression = @expression\n";
4. Hashes i Perl
Hash er et begreb Key Value Pair. Nedenfor er et eksempel til at oprette en hash.
#!/usr/bin/perl
%data = ('Mohan Singh' => 55, 'Ram Gupta' => 25, 'Bhuvan Kumar' => 31);
@age = values %data;
print "$age(0)\n";
print "$age(1)\n";
print "$age(2)\n";
5. Hash-element tilføjelse og fjernelse
#!/usr/bin/perl
%data = ('Mohan Singh' => 55, 'Ram Gupta' => 25, 'Bhuvan Kumar' => 31);
@keys = keys %data;
$size = @keys;
print "a - Hash size: $size\n";
# add an element to the hash;
$data('Imran Khan') = 44;
@keys = keys %data;
$size = @keys;
print "b - Hash size: $size\n";
# delete an element from the hash;
delete $data('Imran Khan');
@keys = keys %data;
$size = @keys;
print "c - Hash size: $size\n";
6. Betinget erklæring i Perl: hvis… elsif… andet
#!/usr/local/bin/perl
$num = 50;
# check condition using if statement
if( $num == 40 ) (
# print the following if true
printf "num has a value which is 20\n";
) elsif( $num == 60 ) (
# else print if the next condition is true
printf "num has a value which is 30\n";
) else (
# if none is true print following
printf "num has a value which is $num\n";
)
7. Betinget erklæring i Perl: medmindre… elsif… andet erklæring
#!/usr/local/bin/perl,
$num = 50;
# check condition using unless statement
unless( $num == 25) (
# if condition is false then print the following
printf "num has a value which is not 25\n";
) elsif( $num == 55) (
# if condition is true then print the following
printf "num has a value which is 55";
) else (
# if both the condition is dissatisfied, print the
original value
printf "num has a value which is $num\n";
)
8. Loops i Perl: Mens loop
#!/usr/local/bin/perl
$i = 1;
# while loop
while( $i < 5 ) (
printf "Value of i: $i\n";
$i = $i + 1;
)
9. Loops i Perl: Indtil loop og for loop
#!/usr/local/bin/perl
$i = 1;
# until loop
until( $i > 5 ) (
printf "Value of i: $i\n";
$i = $i + 1;
)
# for loop
for ($j = 0; $j < 3; $j++) (
printf "Value of j: $j\n";
)
10. Loops i Perl: gør… mens Loop
#!/usr/local/bin/perl
$i = 10;
# do…while loop
do(
printf "Value of i: $i\n";
$i = $i + 1;
)
while( $i < 20 );
Avancerede Perl-kommandoer
1. Socket-programmering i Perl: Server
#!/usr/bin/perl -w
# Filename : server.pl
use strict;
use Socket;
# use port 8081 as default
my $port = shift || 8081;
my $protocol = getprotobyname('tcp');
my $server = "localhost"; # Host IP running the
server
# create a socket, make it reusable
socket(SOCKET, PF_INET, SOCK_STREAM,
$protocol)
or die "Can't open socket $!\n";
setsockopt(SOCKET, SOL_SOCKET,
SO_REUSEADDR, 1)
or die "Can't set socket option to SO_REUSEADDR
$!\n";
# bind to a port, then listen
bind( SOCKET, pack_sockaddr_in($port,
inet_aton($server)))
or die "Can't bind to port $port! \n";
listen(SOCKET, 5) or die "listen: $!";
print "SERVER started on port $port\n";
# accepting a connection
my $client_addr;
while ($client_addr = accept(NEW_SOCKET,
SOCKET)) (
# send them a message, close connection
my $name = gethostbyaddr($client_addr,
AF_INET );
print NEW_SOCKET "Smile from the server";
print "Connection recieved from $name\n";
close NEW_SOCKET;
)
2. Socket-programmering i Perl: Client
!/usr/bin/perl -w
# Filename : client.pl
use strict;
use Socket;
# initialize host and port
my $host = shift || 'localhost';
my $port = shift || 8081;
my $server = "localhost"; # Host IP running the
server
# create the socket, connect to the port
socket(SOCKET, PF_INET, SOCK_STREAM, (getproto
byname('tcp'))(2))
or die "Can't create a socket $!\n";
connect( SOCKET, pack_sockaddr_in($port,
inet_aton($server)))
or die "Can't connect to port $port! \n";
my $line;
while ($line = ) (
print "$line\n";
)close SOCKET or die "close: $!";
3. Databaseforbindelse ved hjælp af Perl
#!/usr/bin/per
use DBI
use strict;
my $driver = "mysql";
my $database = "DBTEST";
my $dsn = "DBI:$driver:database=$database";
my $userid = "user123";
my $password = "pass123";
my $dbh = DBI->connect($dsn, $userid, $password
) or die $DBI::errstr;
4. CGI-programmering ved hjælp af Perl
#!/usr/bin/perl
print "Content-type:text/html\r\n\r\n";
print '';
print '';
print 'Hello Perl - CGI Example';
print '';
print '';
print '
Hej Perl! Dette er et CGI-programeksempel
';Print '';
Print '';
1;
Tip og tricks til at bruge Perl-kommandoer
Det siges, at Perl er en blanding af alle sprog, dvs. at den er udstyret med de bedste funktioner i større programmeringssprog. Det vigtigste aspekt er at mestre det grundlæggende og gå videre med udøvelsen af dette sprog. Opgradering og selvforbedring er nøglen til succes.
Konklusion
Ovenstående programmer er eksempler, som hjælper en enhed med at forstå det grundlæggende og fortsætte med selvforbedring. Dette er blevet sagt som et grimt programmeringssprog, men det viser faktisk en lang række funktioner. Det anbefales at følge dette dokument for at udarbejde koder og forstå, hvad der sker i selve programmet.
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