Taking input from the keyboard

Taking input from the keyboard:--

in PERL defined filehandle, which points to the standard input device for the program. can be used to read either single line of text or multiple lines of texts from standard input.

To read a single line of text
$var=
where $var is the scalar variable.

Note: If the line read from the STDIN is not assigned to the variable then PERL assigns that line to a special variable called $_ .

while($line=){
print “$line”;
last if($line eq “quit\n”);
}


To read the multiple line of text into an array
@array=;

Example:

1. To take 10 inputs from the keyboard and calculate its sum.

#!c:\perl\bin\perl.exe
print"Content-type:text/html\n\n";

$i=1;
$sum=0;
print "Enter 10 numbers\n";
while($i<=10) { $a=;
$sum+=$a;
$i++;
}
print "Sum=$sum";


2. Validate the username and password supplied from the keyboard to that of data
stored in database.
#!c:/perl/bin/perl.exe
print"Content-type:text/html\n\n";

require "cgi-lib.pl";
use Win32::ODBC;

print "enter the username:";
$username=;
chomp($username);
print "enter the password:";
$password=;
chomp($password);
if(!($Db=new Win32::ODBC("dsn=database;UID=;PWD=")))
{
print "Not connected";
exit;
}

else
{
print"Connected\n";
if(!$Db->sql("SELECT uname,pwd from hello where uname=\'$username\'"))
{

if($Db->FetchRow())
{
@data=$Db->Data();
if(($data[0] eq $username) && ($data[1] eq $password)){
print "\nValid user";
}
else{print"Invalid user";}
}
else
{
print"Username not found";
}
}

else
{
print"Not executed";
exit;
}
}


Opening and closing a file

Perl provides the open() function to open a file in the directory.

Syntax:
open(FILEHANDLE, );

Here first argument is an identifier called a filehandle. And the second argument is the filename which is enclosed in double quotes.

We use unless to check the error during opening.







Example: 1. Opening a file and checking error

#!C:/perl/bin/perl.exe
print"Content-type:text/html\n\n";

unless(open(test,"text.txt")){
print "Unable to open file\n";
exit;
}
print "File opened successfully\n";

2. Opening a file and writing some text in it

#!C:/perl/bin/perl.exe
print"Content-type:text/html\n\n";

unless(open (test,">test.txt")){
print "Unable to open file";
exit;
}
print "File opened and writing to file \n";
$line=" hello";
print test " $line"; #writing the content to a file
close test; Closing of filehandle

open(test,"test.txt");
@test=;
print "The new conent of the file is: @test"; Reading from the file