perl examples

Example 1: Input two number, output sum

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#!/usr/bin/perl

$doagain = "yes";

while($doagain eq "yes") {
 $x = &getnumber;
 $y = &getnumber;

 $z = $x + $y;

 print "$x + $y = $z\n";

 print "$x + $y = $z\n";

 print "Do it again? (yes or no) ";
 $doagain = <STDIN>;

 chop($doagain);

}
sub getnumber {

      print "Type in a number: \n";

 $number = <STDIN>;
 chop($number);

 while($number =~ /\D/){ # not non-digit, i.e digit[0-9]

 print "$number is not a number\n";
 print "Enter a number ";
 $number = <STDIN>;

 chop($number);
 }
 $number;
}

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Example 2: find a file in a directory and its sub-directory
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#!/usr/bin/perl

#
# search for a file in all subdirectories
#
if ($#ARGV != 1) {
print "usage: find_file filename directory\n";
exit;
}

$filename = $ARGV[0]; #first argument

# look in the directory
$dir = $ARGV[1]; #second argument
&searchDirectory($dir);

sub searchDirectory {
local($dir); #local variable
local(@lines);
local($line);
local($file);
local($subdir);

$dir = $_[0];
# check for permission
if(-x $dir) {

    # search this directory
    @lines = `cd $dir; ls -l | grep $filename`;
    foreach $line (@lines) {
#\d  # Any digit. The same as [0-9]
#\D  # Any non-digit. The same as [^0-9]
#\s  # Any whitespace character: space,
#\S  # Any non-whitespace character
       # tab, newline, etc

        $line =~ /\s+(\S+)$/; #  end of line
        $file = $1;
        print "Found $file in $dir\n";
    }

    # search any sub directories
                                  
    @lines = `cd $dir; ls -l`;
    foreach $line (@lines) {
        if($line =~ /^d/) { # beginning of line containing d (directory)
            $line =~ /\s+(\S+)$/;
            $subdir = $dir."/".$1;
            &searchDirectory($subdir);
        }
    }
}
}

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example 3
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#!/usr/bin/perl
#$b and $c as strings
$b='3';

$c='2';
$a = $b . $c;   # Concatenate string $b and $c
print "$a \n";

$a = $b x $c;   # string $b repeated $c times
print "$a \n";
@food  = ("apples", "pears", "eels");

print "$food[2] \n"; #array starting from 0
push(@food, "eggs", "lard");

print "@food \n";
foreach $morsel (@food)         # Visit each item in turn
                                # and call it $morsel
{

        print "$morsel\n";      # Print the item
        print "Yum yum\n";      # That was nice
}

for ($i = 0; $i < 10; ++$i)     # Start with $i = 1

                                # Do it while $i < 10
                                # Increment $i before repeating
{
        print "$i\n";
}
print "Password? ";             # Ask for input
$a = <STDIN>;                   # Get input
chop $a;                        # Remove the newline at end

while ($a ne "fred")            # While input is wrong...
{
    print "sorry. Again? ";     # Ask again
    $a = <STDIN>;               # Get input again
    chop $a;                    # Chop off newline again

}

if ($a)
{
        print "The string is not empty\n";
}
else

{
        print "The string is empty\n";
}