celsobarriga-dot-com

Base64 Encoding and Decoding

celso — Thu, 28 May 2009 18:10:31 +0000

At one time, I needed to encode and decode strings in Base64 but I was on a very old Perl version that does not include the MIME::Base64 core module, nor am I able to install the said module. So, here’s the source for encoding and decoding Base64 ripped from the MIME::Base64 module:

sub EncodeBase64
{
    my $s = shift ;
    my $r = '';
    while( $s =~ /(.{1,45})/gs ){
        chop( $r .= substr(pack("u",$1),1) );
    }
    my $pad=(3-length($s)%3)%3;
    $r =~ tr|` -_|AA-Za-z0-9+/|;
    $r=~s/.{$pad}$/"="x$pad/e if $pad;
    $r=~s/(.{1,72})/$1\n/g;
    $r;
} 

sub DecodeBase64
{
    my $d = shift;
    $d =~ tr!A-Za-z0-9+/!!cd;
    $d =~ s/=+$//;
    $d =~ tr!A-Za-z0-9+/! -_!;
    my $r = '';
    while( $d =~ /(.{1,60})/gs ){
        my $len = chr(32 + length($1)*3/4);
        $r .= unpack("u", $len . $1 );
    }
    $r;
}

Skydiving video

celso — Mon, 25 May 2009 14:40:08 +0000

Look what I did last weekend! I went for a tandem skydive at Pepperell, MA on May 24th, 2009. What a rush; it was an awesome experience!

Read string from stdin using fgets

celso — Thu, 26 Feb 2009 19:44:37 +0000

#include <stdio.h>
#include <string.h>

int main(void)
{
  char str[80];
  int i;

  printf("Enter a string: ");
  fgets(str, 10, stdin);

  /* remove newline, if present */
  i = strlen(str)-1;
  if( str[ i ] == '\n')
      str[i] = '\0';

  printf("This is your string: %s", str);

  return 0;
}

How to determine DST time changes

celso — Fri, 01 Feb 2008 17:44:28 +0000

Here’s how to determine the dates when the Daylight Savings Time changes for a given year (I keep forgetting how to do this.):



zdump -v /etc/localtime|grep 2008

/etc/localtime  Sun Mar  9 06:59:59 2008 UTC =
    Sun Mar 9 01:59:59 2008 EST isdst=0 gmtoff=-18000
/etc/localtime  Sun Mar  9 07:00:00 2008 UTC =
    Sun Mar 9 03:00:00 2008 EDT isdst=1 gmtoff=-14400
/etc/localtime  Sun Nov  2 05:59:59 2008 UTC =
    Sun Nov 2 01:59:59 2008 EDT isdst=1 gmtoff=-14400
/etc/localtime  Sun Nov  2 06:00:00 2008 UTC =
    Sun Nov 2 01:00:00 2008 EST isdst=0 gmtoff=-18000

Obviously, change 2008 to whatever year you want.

Uninstall Perl Module

celso — Thu, 10 Jan 2008 21:00:41 +0000

Here's how to cleanly uninstall any Perl module:

#!/usr/local/bin/perl

use ExtUtils::Packlist;
use ExtUtils::Installed;

$ARGV[0] or die "Usage: $0 Module::Name\n";

my $mod = $ARGV[0];

my $inst = ExtUtils::Installed->new();

foreach my $item (sort($inst->files($mod))) {
         print "removing $item\n";
         unlink $item;
}

my $packfile = $inst->packlist($mod)->packlist_file();
print "removing $packfile\n";
unlink $packfile;

Find Out the Top 10 CPU Hogs

celso — Wed, 29 Aug 2007 21:48:23 +0000

I found this command useful in finding out which top 10 processes are hogging my CPU resources. Note that this command is specific to the Red Hat flavor of Linux. See the man page for ps for the correct output format to use for your specific platform:

ps -eo pcpu,pid,user,args | sort -k1 -r | head -11

Substitue pcpu above with pmem to see the memory hogs instead.

Bourne Shell Logging Routine

celso — Wed, 29 Aug 2007 03:20:19 +0000

Here’s another logging routine, this one is written in Bourne shell:

#!/bin/sh

log_message() {
    echo `date "+%m/%d/%y %H:%M:%S %Z"` "$1" | tee -a aaa.out
}

log_message "Hello there"
log_message "Goodbye"

Sample output:

08/28/07 23:16:13 EDT Hello there
08/28/07 23:16:13 EDT Goodbye

Setting MySQL Password

celso — Wed, 23 Aug 2006 17:40:47 +0000

To set up root password the first time:

$ mysqladmin -u root password NeWPasSwORd

To change an existing root password:

$ mysqladmin -u root -p oldpassword newpass
Enter password:

To change a normal user password:

$ mysqladmin -u dbuser-p oldpassword newpass

Sorting IP Addresses

celso — Thu, 13 Jul 2006 18:12:42 +0000

The following will sort an array of IP addresses in @in and the sorted IP addresses will be in @out.

@out = sort {
    pack('C4' => $a =~ /(\d+)\.(\d+)\.(\d+)\.(\d+)/)
    cmp
    pack('C4' => $b =~ /(\d+)\.(\d+)\.(\d+)\.(\d+)/)
} @in;

What this does is it forms a string of four bytes out the IP address octet using the pack() function then sorts it lexicographically.

Determining the External IP Address

celso — Wed, 07 Jun 2006 17:33:15 +0000

Here’s how to find out your external IP address courtesy of this hint:

http://www.macosxhints.com/article.php?story=20060602180942480


curl --silent http://checkip.dyndns.org
    | awk '{print $6}' | cut -f 1 -d "<"

If you are using Apple’s Airport Extreme Basestation (mine is particularly the Time Capsule and this is where I have tested this), and you have the SNMP interface enabled, you can run the following command


prompt$ snmpwalk -Os -c public -v 1 192.168.63.1 ipAdEntAddr IpAddress \
    | grep -E -v '(127.0.0|169.254|192.168.63.1)' \
    | cut -d : -f 2 | sed 's/ //g'