Sissejuhatus Perli käskudesse
Perl on programmeerimiskeel. Kui varem oli see mõeldud ainult teksti redigeerimiseks, kasutatakse seda nüüd paljudel eesmärkidel, näiteks süsteemi administreerimiseks Linuxis, veebiarenduseks, võrgu programmeerimiseks jne. Perli peaarhitekt ja looja on Larry Wall. See loodi 1987. aastal ja seda kasutatakse endiselt peamise programmeerimiskeelena. Perl on kõrgetasemeline keel. See on ka tõlgendatud ja dünaamiline programmeerimiskeel. Nüüd õpime Perli käske üksikasjalikult.
Põhilised Perli käsud
1. Põhiline Perli käsk Perlis printimiseks
#!/usr/bin/perl
# This will print "Hello, World"
print "Hello, world\n";
2. Üherealine kommentaar Perlis
#!/usr/bin/perl
# This is a single line comment
print "Hello Perl\n";
3. Mitme rea kommentaar Perlis
#!/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. Muutuja määramine Perlis (topelt tsiteeritud muutujate interpoleerimine)
#!/usr/bin/perl
$a = 10;
print "Variable a = $a\n";
5. Põgenemismärk Perlis
#!/usr/bin/perl
$a = "This is \"Perl\"";
print "$a\n";
print "\$a\n";
6. Perlis on keelpillide käitumine topelt- ja ühekohaliste jutumärkidega erinev. Kui topelt jutumärgid võimaldavad interpoleerimist, siis ühekordsed jutumärgid seda ei tee.
#!/usr/bin/perl
# Interpolation example.
$str = "Hello \nPerl";
print "$str\n";
# Non-interpolation example.
$str = 'Hello \nPerl';
print "$str\n";
7. Suur juhtum Perli käsus
#!/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. Skaalaarse muutuja määramine Perlis
#!/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. Lihtsad skalaaroperatsioonid Perlis
#!/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 = $connumstr\n";
10. Spetsiaalsed kirjandused Perlis
#!/usr/bin/perl
print "Current file name ". __FILENAME__ . "\n";
print "Current Line Number " . __LINENO__ ."\n";
print "Current Package " . __PACKAGENAME__ ."\n";
# here they cannot be interpolated
print "__FILENAME__ __LINENO__ __PACKAGENAME__\n";
Vahepealsed Perli käsud
1. Massiivid Perlis
Massiivi indeks algab 0. Negatiivne indeks näitab elemente viimasest positsioonist. Allpool toodud näide.
#!/usr/bin/perl
@weekday = qw/Mon Tue Wed Thu Fri Sat Sun/;
print "$weekday(0)\n";
print "$weekday(1)\n";
print "$weekday(2)\n";
print "$weekday(6)\n";
print "$weekday(-1)\n";
print "$weekday(-6)\n";
2. Jada elementide massiivid
#!/usr/bin/perl
@oneToTen = (1..10);
@fiftyToSeventyfive = (50..75);
@aToZ = (a..z);
print "@oneToTen\n"; # Prints one to ten
print "@fiftyToSeventyfive\n"; # Prints fifty to seventy five
print "@aToZ\n"; # Prints from a to z
3. Massiivi elementide lisamine ja eemaldamine
#!/usr/bin/perl
# creating an array
@expression = ("happy", "sad", "angry");
print "1. \@expression = @expression\n";
# add element to the end of the arraypush(@expression, "jolly");
print "2. \@expression = @expression\n";
# add element to the beginning of the arrayunshift(@expression, "excited");
print "3. \@expression = @expression\n";
# remove element to the last of the array.pop(@expression);
print "4. \@expression = @expression\n";
# remove element from the beginning of the array.shift(@expression);
print "5. \@expression = @expression\n";
4. Räsid Perlis
Hash on võtmeväärtuse paari mõiste. Allpool on näide räsi loomiseks.
#!/usr/bin/perl
%data = ('Mohan Singh' => 55, 'Ram Gupta' => 25, 'Bhuvan Kumar' => 31);
@age = values %data;
print "$age(0)\n";
print "$age(1)\n";
print "$age(2)\n";
5. Lühikese elemendi lisamine ja eemaldamine
#!/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. Tingimuslik avaldus Perlis: kui… elsif… muidu
#!/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. Tingimuslik avaldus Perlis: kui… elsif… muu avaldus
#!/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. Silmused Perlis: kui silmus
#!/usr/local/bin/perl
$i = 1;
# while loop
while( $i < 5 ) (
printf "Value of i: $i\n";
$i = $i + 1;
)
9. Silmused Perlis: kuni silmuseni ja silmuse jaoks
#!/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. Silmused Perlis: tehke … samal ajal kui silmus
#!/usr/local/bin/perl
$i = 10;
# do…while loop
do(
printf "Value of i: $i\n";
$i = $i + 1;
)
while( $i < 20 );
Täpsemad Perli käsud
1. Pesa programmeerimine Perlis: 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. Pesa programmeerimine Perlis: klient
!/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. Andmebaasi ühenduvus Perli abil
#!/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 programmeerimine Perli abil
#!/usr/bin/perl
print "Content-type:text/html\r\n\r\n";
print '';
print '';
print 'Hello Perl - CGI Example';
print '';
print '';
print '
Tere, Perl! See on CGI programmi näide
';printida '';
printida '';
1;
Perli käskude kasutamise näpunäited
Väidetavalt on Perli segu kõigist keeltest, st see on varustatud peamiste programmeerimiskeelte parimate omadustega. Kõige olulisem on õppida põhitõdesid ja jätkata selle keele harjutamist. Uuendamine ja enesetäiendamine on edu võti.
Järeldus
Ülaltoodud programmid on näidised, mis aitavad üksusel mõista põhitõdesid ja jätkata enesetäiendamist. Seda on räägitud koledast programmeerimiskeelest, kuid tegelikult esitleb see väga erinevaid funktsioone. Koodide koostamiseks ja programmis endas toimuva mõistmiseks on soovitatav seda dokumenti järgida.
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See on olnud Perli käskude juhend. Siin oleme arutanud nii Perli, nii vahetu kui ka edasijõudnute käskude üle. Lisateabe saamiseks võite vaadata ka järgmist artiklit -
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