Bits, Bytes and Me

I just need the file name!

2009-06-19T17:04:00.005-04:00

I am always downloading files from the command prompt using curl or wget. Sometimes I like to automate the download process. One thing I found to be helpful is using sed to extract the file name from the URL.

I created the following bash script in utilizing my sendmail.pl Perl script found in Why wait for a download?. I called the following script DownloadAndEmailMe.sh. Here it is.

#!/bin/bash
curl -O $1
filename=`echo $1 | sed 's/\(.*\)\///'
perl /path/to/sendmail.pl localhost youremail@gmail.com youremail@gmail.com
"Download Done: $filename" "The following file is done downloading: $filename"

Of course there are a few things to change in the script above to make it yours:
1. Change /path/to/sendmail.pl to your own path to sendmail.pl
2. Change localhost to your own SMTP server name.
3. Change youremail@gmail.com to your own email.

This is how I run it

DownloadAndEmailMe.sh http://mirrors.easynews.com/linux/ubuntu-releases/jaunty/ubuntu-9.04-desktop-i386.iso

When the download is done it will send you a nice email that reads:
The following file is done downloading: ubuntu-9.04-desktop-i386.iso

I would also recommend looking at sed and see how it works. I use it a lot. It's very powerful.

Watching Hard Drive Activity

2009-06-16T16:41:00.002-04:00

On Linux systems I use top all the time, but there is another tool called iotop which lets you watch disk IO on your system.

Here is how to install it on Ubuntu

sudo apt-get install iotop

It's really cool. Thanks Josh for finding it.

Sync directories with rsync

2009-06-16T12:04:00.011-04:00

Sometime I need some directories synchronized between 2 different machines.

I use rsync to get the task done, my command would look like this:

rsync -zae "ssh" /path/to/local/dir/ remoteHost:/path/to/remote/dir/

To learn more bout rsync command visit the man pages

Every time you run this command you will be prompted for a password, which is OK if you run the sync manually. If you like to use cron to schedule the sync, you will need to refer to my post SSH without a password to do it.

SSH without a password

2009-06-15T15:27:00.012-04:00

I like to log on to my remote hosts without a password, it saves you from prying eyes, and it helps you automate certain things, like backups. This is how to do it:

1. Generate your public/private keys using ssh-keygen.

ssh-keygen -t rsa

Note: Leave passphrase empty

2. Copy id_rsa.pub to the .ssh directory of the remote host you want to log on to as authorized_keys2.

scp ~/.ssh/id_rsa.pub foo@remoteHost:~/.ssh/authorized_keys2

Note: If you have other keys in authorized_keys2 make sure not to overwrite it but append the new one to it.

3. SSH to the remote host and make authorized_keys2 writeable only to the user

chmod 644 ~/.ssh/authorized_keys2

Next time you log on to your remote host it will not prompt you for a password.

Why wait for a download?

2009-06-12T16:53:00.021-04:00

Say you have to download the latest Ubuntu cd, but you don't want to just sit there until it's done. I like to start it and get an email on my Blackberry when it's done.

Step 1: Open a terminal window, Create a Perl script called sendmail.pl. You can use any editing tool, I prefer vi myself. Insert the following code in the file and save it.

#!/usr/bin/perl -w
use Net::SMTP;
if ($#ARGV != 4) {
print "usage:mailsever to from subject body\n";
exit;
}
my($mailServer) =$ARGV[0];
my($to)=$ARGV[1];
my(@mailTo)=split(/,/, $to);
my($mailFrom)=$ARGV[2];
my($mailSubject)=$ARGV[3];
my($mailBody)=$ARGV[4];
$smtp = Net::SMTP->new($mailServer);
$smtp->mail($mailFrom);
$smtp->recipient(@mailTo);
$smtp->data();
$smtp->datasend("To: " . $ARGV[1] . "\n");
$smtp->datasend("Subject: " . $mailSubject . "\n");
$smtp->datasend("\n");
$smtp->datasend($mailBody . "\n");
$smtp->dataend();
$smtp->quit;

Step 2: I use a tool like wget or curl to download a url

wget url
curl -O url

Step 3: All together, Step 1 and 2, command syntax

wget url; perl sendmail.pl mailserver to from subject body;

My command will look something like this

wget http://mirrors.easynews.com/linux/ubuntu-releases/jaunty/ubuntu-9.04-desktop-i386.iso; perl sendmail.pl localhost youremail@gmail.com youremail@gmail.com
"I am Done" "Download is done, file is ready";

Make sure to replace youremail@gmail.com with a valid email address.
In the above example, I am using localhost as the SMTP server.

After your file is done downloading you will get an email.
Note: This could also be used for any long running process.

Google Checkout

2009-06-12T16:40:00.002-04:00

It seems to be a Google kind of day. Have you ever used Google Checkout? it seems to be a new way of checking out at a lot of online vendors. It's similar to PayPal. It makes it much easier to checkout, instead of putting in all your credit card information every time. Yes you must sign up for a Google account!

Google Reader

2009-06-12T16:31:00.001-04:00

I seem to be addicted to Google Reader. Every chance I get when I am online I click the short-cut. I think it's great, it just has a cool way of displaying the RSS feeds. Check it out for yourself, you should get a Google account of course.

Reboot Blackberry

2009-06-11T10:32:00.008-04:00

You can reboot your Blackberry without taking the battery out.
Next time you Blackberry needs a reboot try this:
ALT-Right CAP-DEL
All at the same time.

Secure Delete

2009-06-11T07:14:00.009-04:00

I was working on a sensitive file on my Mac, when I was done with it, I wanted to delete it securely. Since I love to do things in the Terminal, I found this neat command called "srm" which stands for, you guessed it, secure remove.

Usage: srm <filename>

It takes a little longer than normal rm but its worth it for the security.

It also works on Linux systems, you will need to install it. On Ubuntu just type:

sudo apt-get install secure-delete

If you're a Windows user there is a tool called "sdelete" from Microsoft.

Blackberry Troubleshooting

2009-06-10T19:18:00.001-04:00

Did you know that while at the home screen on your Blackberry typing ALT-LGLG you will get an event log.
Maybe the next time your Blackberry is acting up, you can try to look at the log and see what is happening.

OH NO, Ubuntu is not booting!

2009-06-10T19:10:00.003-04:00

My boss called me on the phone and asked if I can take a look at his laptop.
He could not boot into Ubuntu Jaunty(9.04). He kept getting the following error: "group descriptors corrupted"
"That doesn't sound too good", I said. After searching the web for the solution, I found it.
I booted the laptop from the only Live-CD I had handy at the time, Ubuntu 8.10 Install/Live-CD.
Once it came up, I opened the terminal and typed the following.

sudo fsck -y /dev/sdb1

After 10 minutes of fixing the filesystem on the hard drive, it was done.
I rebooted the laptop, Jaunty(9.04) came up. My boss was happy.