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@ ever4st
2025-01-18 20:46:35Introduction to Perl programming
Perl is a high-level, general-purpose programming language that excels in text processing, system administration, web development, and more. Its flexibility and strong regular expression capabilities make it a popular choice for scripting tasks. This article introduces the basics of Perl programming, including an example script.
Basics of Perl
Running a Perl Script
To execute a Perl script, save the code in a file with a
.plextension (e.g.,script.pl) and run it from the command line:bash perl script.plSyntax Highlights
- Shebang Line: Specify the interpreter.
perl #!/usr/bin/perl - Comments: Use
#for single-line comments.perl # This is a comment - Printing Output:
perl print "Hello, World!\n";
Variables
Perl has three main variable types: - Scalars: Single values (numbers, strings, etc.), prefixed by
$.perl my $name = "Eva"; my $age = 35;- Arrays: Ordered lists, prefixed by@.perl my @colors = ("red", "green", "blue");- Hashes: Key-value pairs, prefixed by%.perl my %capitals = ("France" => "Paris", "Japan" => "Tokyo");Control Structures
- Conditional Statements:
perl if ($age > 18) { print "You are an adult.\n"; } else { print "You are a minor.\n"; } - Loops:
perl for my $color (@colors) { print "$color\n"; }
Example Script: Text File Analysis
This script reads a text file, counts the lines, words, and characters, and prints the results.
Script
```perl
!/usr/bin/perl
use strict; use warnings;
Check for file argument
if (@ARGV != 1) { die "Usage: $0
\n"; } my $filename = $ARGV[0];
Open the file
open(my $fh, '<', $filename) or die "Could not open file '$filename': $!\n";
Initialize counters
my ($line_count, $word_count, $char_count) = (0, 0, 0);
Process the file
while (my $line = <$fh>) { $line_count++; $char_count += length($line); $word_count += scalar(split(/\s+/, $line)); }
close($fh);
Print results
print "File: $filename\n"; print "Lines: $line_count\n"; print "Words: $word_count\n"; print "Characters: $char_count\n"; ```
Explanation
- Input Validation: Ensures the script is called with a filename.
- File Handling: Uses
openandclosefor file operations. - Counters: Tracks lines, words, and characters.
- Loop: Reads the file line by line, processing each line.
Running the Script
Save the script as
file_analysis.pland run it with a text file:bash perl file_analysis.pl sample.txtConclusion
Perl is a powerful tool for scripting and data processing. Its concise syntax and robust text-handling capabilities make it an excellent choice for many tasks. This example demonstrates basic Perl features and encourages further exploration of its vast capabilities.
- Shebang Line: Specify the interpreter.