Perl | Shafiq Alibhai

A Beginner's Guide to Perl Expect Bindings - A Simple Walkthrough

21 February 2012

Basic Perl “Hello World” Script (hello.pl)#

Let’s start with the basics. Here is a straightforward “Hello World” script written in Perl. Create a new file and name it hello.pl.

#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;

print "-----------\n",
      "Hello World\n",
      "-----------\n";

In this script, we’re using Perl’s built-in modules for error handling (use strict; use warnings; use diagnostics;) to make sure the code is robust.

Introducing Expect Bindings with Perl (test.pl)#

Now, let’s dive into the main topic: how to use Expect bindings in a Perl script. Create another file, test.pl, and add the following code:

How To Get The Current Epoch Time (Unix Timestamp)

30 September 2010

Development

Bash, Perl, Java, Erlang, How-To

PHP
PostgreSQL
powershell
Python
ruby
shell
sql server
unix
Unix Timestamp
vbscript

disableHLJS: false#

Perl:

time

PHP:

time()

Ruby:

Time.now # (or Time.new). To display the epoch: Time.now.to_i

Python:

import time # first, then int(time.time())

Java:

long epoch = System.currentTimeMillis()/1000;

Microsoft .NET C#:

epoch = (DateTime.Now.ToUniversalTime().Ticks - 621355968000000000) / 10000000;

VBScript/ASP:

DateDiff("s", "01/01/1970 00:00:00", Now())

Erlang:

calendar:datetime_to_gregorian_seconds(calendar:now_to_universal_time( now()))-719528*24*3600. # OR element(1, now()) * 10000 + element(2, now()).

MySQL:

SELECT unix_timestamp(now())

PostgreSQL:

SELECT extract(epoch FROM now());

Oracle PL/SQL:

SELECT (SYSDATE - TO_DATE('01-01-1970 00:00:00', 'DD-MM-YYYY HH24:MI:SS')) * 24 * 60 * 60 FROM DUAL

SQL Server:

SELECT DATEDIFF(s, '1970-01-01 00:00:00', GETUTCDATE())

JavaScript:

Math.round(new Date().getTime()/1000.0) // getTime() returns time in milliseconds.

Unix/Linux Shell:

date +%s

PowerShell:

Get-Date -UFormat "%s" # Produces: 1279152364.63599

Actionscript:

(new Date()).time

Other OS’s Command line:

perl -e "print time" # (If Perl is installed on your system)

ColdFusion (CFML) MX 6.1+:

#int( getTickCount() / 1000 )#

Bash Command Line:

date +%s

Perl – system load

7 September 2010

Development

Perl, Awk, Cli, Monitoring, Code-Snippet

To find the system load use the following perl snippet :

System load of last one minute :

my $system_load = exec('<a class="zem_slink" title="Uptime" rel="wikipedia" href="http://en.wikipedia.org/wiki/Uptime">uptime</a> | awk -F "load average: " \'{ print $2 }\' | cut -d, -f1');
my $system_load = qx('uptime | awk -F "load average: " \'{ print $2 }\' | cut -d, -f1');

System load of last 5 minutes :

my $system_load = exec('uptime | awk -F "load average: " \'{ print $2 }\' | cut -d, -f2');
my $system_load = qx('uptime | awk -F "load average: " \'{ print $2 }\' | cut -d, -f2');

System load of last 15 minutes :

my $system_load = exec('uptime | awk -F "load average: " \'{ print $2 }\' | cut -d, -f3');
my $system_load = qx('uptime | awk -F "load average: " \'{ print $2 }\' | cut -d, -f3');

Perl – How to Read a Text File into a Variable – 6 ways to do it

15 March 2010

Development

Perl, File-Handling, Tutorial, Code-Snippet

6 Ways to Read a Text File into a Variable

If you are working with large file(s) you might consider using File::Slurp. It is much fast than the conventional:

{
  local $/=undef;
  open FILE, "myfile" or die "Couldn't open file: $!";
  binmode FILE;
  $string = &lt;FILE>;
  close FILE;
}

{
  local $/=undef;
  open FILE, "myfile" or die "Couldn't open file: $!";
  $string = &lt;FILE>;
  close FILE;
}

open FILE, "myfile" or die "Couldn't open file: $!";
$string = join("", &lt;FILE>);
close FILE;
  
open FILE, "myfile" or die "Couldn't open file: $!";
while (&lt;FILE>){
 $string .= $_;
}
close FILE;

open( FH, "sample.txt") || die("Error: $!\n");
read(FH, $data, 2000);
close FH;

The format for the read function is: