Simple Perl Programs

Perl - Practical Extraction and Report Language

Perl is an interpreted scripting language.

Perl is optimised for scanning arbitrary text files and system administration.

It has built-in extended regular expression matching and replacement, a data-flow mechanism to improve security with setuid scripts and is extensible via modules that can interface to C libraries.


Installation :

sudo apt-get install perl

Compiling method :

perl filename.pl

e.g perl hello.pl


1. Simple mathematical calculation program

 #usr/bin/perl
$str = " Hello ";
print "cse:$str \n";
print "2+2 = ",2+2,"\n";
print "log(1e23) = ",log(1e23),"\n";
print "sin(3.141) = ",sin(3.141), "\n";

2. Pattern Matching Program

 $_="hello how are you";
if(/hello/){
print "Default Variable = $_ \n";
print "Found hello \n";
}
# i modifier ignore case difference
if(m/HOw/i){
print "found how \n";
}
#match with negation
if(!/hall/){
print "Not found hall \n";
}
else {
 print "found\n"; }

3. System Command Accepting Program

$time = localtime;
print "Time is now - $time \n";
print "Enter a shell command:";
$n = <STDIN>;
system $n;

4. Program for Counting Words, Lines and Characters in a File

#usr/bin/perl
$filen = "fileh.pl";
open($fh,"<",$filen);
while($line = <$fh>){
@lines = [split(/ +/,$line)];
$noline += scalar(@lines);
$words += scalar(split(/\w+/,$line));
$chars += length($line);
}
print "\n No.of Lines - $noline \n
       No.of Words - $words \n
       No.of Characters - $chars \n"; 
close($fh);

5. Program for Printing all 5 letter words in Paragraph by giving as it as input

print "Enter a text:";
while(<>){
chop;
tr/;:;.!?-//d;
foreach $w (split) {
  if(length($w)==5) {
    print "$w \n";
    $score++;
          }
    }}

6. Program for Printing the words which are all end with "ly"

print "Enter the text:";
while (<>) {
   foreach $wd(split){
       if($wd =~ /ly$/i) {
         print " $wd \n";        
         $var++;      
            }
         }}

  

7. Program to find average length of words in a text.


#! usr/bin/perl
use strict;
open (FILE,"wel.txt") or die "error in open wel.txt";

my $TSentences=0;
my $TWords=0;
my $TLetters=0;
my $AvgWordLength=0;
my $AvgSentenceLength=0;

while(my $line=<FILE>)
{
my @words=split(" ",$line);
my $nwords=@words;#no of words in that line
for(my $i=0;$i< $nwords;$i=$i+1)
{
          my @letters=split("",$words[$i]);
          my $nletters=@letters;
          $TLetters=$TLetters+$nletters;
        }
$TWords=$TWords+$nwords;
$AvgWordLength=$TLetters/$TWords;
}

print("Total Words:$TWords\n");
print("Total letters:$TLetters\n\n");
print("The average word length (in characters):$AvgWordLength\n ");
close(FILE);
open (FILE,"wel.txt") or die "error in open wel.txt";

while(my $ch=getc(FILE))
{
  if($ch eq "." || $ch eq "!" || $ch eq "?")
{
     $TSentences=$TSentences+1;
  }
}
$AvgSentenceLength=$TWords/$TSentences;
print("Total sentences:$TSentences\n");
print("The average sentence length (in words):$AvgSentenceLength \n");

exit(0);

8. Program to count the frequency of words in text


# Clear word hash
%words = ();
print "What is the text you wish to analyze? \n";
print "Please include the filename and extension \n\n";
$textfile = <>;                                   # Read the filename from the keyboard input
chop $textfile;                                                # Remove line return
print "Now analyzing lexical frequency in $textfile\n\n";
open text_in, "< $textfile";
while ($line = <text_in>) {
   chomp($line);                                                           # Remove line returns
   $line = lc($line);                                                       # Change to lower case
   $line = ' ' . $line . ' ';                                                 # Add spaces
   $line =~ s/["(),;:.!?]/ /g;                                            # Remove punctuation
   @words = split (" ", $line );                                     # Put words into an array
      foreach $word (@words) {
         $words{$word} = $words{$word} + 1;             # Put word and word frequency in hash
      } #end foreach word
} #end while
close text_in;
# Display the results
foreach $word (sort keys %words) {                          # Sort the word hash
   print "$word $words{$word}\n";                        # Print word and frequency
   }