$ i=107
$ if [ $i -gt 100 ]
> then
> echo “Wow, i got all the way up to $i”
> else
> echo “i is only up to $i”
> fi
Wow, i got all the way up to 107
$ i=22
$ if [ $i -gt 100 ]
> then
> echo “Wow, i got all the way up to $i”
> else
> echo “i is only up to $i”
> fi
i is only up to 22

Here we see a simple if statement. When executed the expression within the brackets is evaluated to either true or false. If the expression is found to be true the commands after the then will be executed, otherwise the commands after the else are executed.

The expression shown here is the greater than expression (>). The symbols we typically use for greater than and less than have specific significance in the UNIX shell, so to compare values we use -gt for greater than and -lt for less than. Comparisons can also be made between strings of text. More information about comparing text and numbers can be found in my book.

For more information like this check out my book Oracle Shell Scripting, only $34.95 from Rampant TechPress.

Buy it now!

OK, so 8.0 isn’t the greatest rating ever, but given that they take into account relevance of content (relevant to what I don’t know) and frequency of updates (there is no April) I’m pretty happy with it.

Now, if you’re interested in the best technology blogs around, check out their Technology Blog Directory. Many of the top picks are focused, professional blogs, not like the crap you’ll find here. There’s some great stuff to check out though and in general I would agree with their rankings.

A. Tucker “Rat” writes:

Oracle administrators of all levels will find benefit in this book. The author has put together the basics in shell scripting and OS fundamentals in aid of maintaining and monitoring scalable production Oracle environments. Each example is easy to read and follow and leaves the reader with room to explore and extrapolate on their own with little effort. A great lookup source for old timers and “must have” for newbies.

I highly recommend this book
-Rat

Thanks for the great review Rat!

Check out my book Oracle Shell Scripting, only $34.95 from Rampant TechPress.

Buy it now!

Coming soon from Belkin this small device offers surge protection for your laptop and devices when you travel and also has two USB charging ports! You should be able to charge many cell phones (like the Razr or Blackberry) and devices like iPods right off the USB ports eliminating the need to keep your computer awake while your devices charge. This should also be nice if you want to leave the computer behind but still need a way to charge your iPod (it’s been a long time since iPods came with 110 volt chargers.)

Belkin is listing the surge protector with a modest $25 price on their site and list it as “Coming soon”. As soon as this becomes available I’ll grab one and post a review here.

via the Daily Giz Wiz podcast

$ env
TERM=vt102
SHELL=/bin/bash
SSH_CLIENT=192.168.2.1 54620 22
OLDPWD=/export/home/oracle
SSH_TTY=/dev/pts/1
USER=oracle
MAIL=/var/mail//oracle
PATH=/usr/bin:/usr/ucb:/etc:.
PWD=/u01
TZ=US/Eastern
PS1=$
SHLVL=1
HOME=/export/home/oracle
LOGNAME=oracle
SSH_CONNECTION=192.168.2.1 54620 192.168.2.100 22
_=/usr/bin/env

These are some of the default variables provided by the system. As Oracle users we’re also familiar with shell variables such as $ORACLE_HOME and $ORACLE_SID.

While most of the environmental variables in the output above are set by the system, variables like $ORACLE_HOME need to be set by the user. In the bourne and bash shells, environmental variables are set by giving the variable name, the equal sign (=) and then the value the variable should be set to. The variable must then be exported with the export command so it can become available to subsequent commands.

$ ORACLE_HOME=/u01/app/oracle/product/10.2.0/Db_1
$ export ORACLE_HOME
$ echo $ORACLE_HOME
/u01/app/oracle/product/10gR2/db_1

When setting variables you simply use the variable name; however, as we see in the above example we use the $ prefix to retrieve the value of a variable. You may also see the variable definition followed by the export on the same line separated by a semicolon. The semicolon marks the end of the first command allowing the commands to be executed as if they were on separate lines.

These exported environmental variables typically affect how UNIX and Linux behave or how other commands run. Though not a rule, environmental variable names are typically all uppercase. Lowercase variable names are typically used for local shell variables that are only needed in the current session or script. Local shell variables need not be exported.

$ day=Monday
$ echo $day
Monday

It’s important to remember that shell variables are specific to a session, not a user. That means if you change the environment variables in one session it will not have any effect on other active sessions.

Beyond the familiar Oracle related shell variables we’ll be using shell variables for storing date information, file and directory names, passwords and much more.

For more information like this check out my book Oracle Shell Scripting, only $34.95 from Rampant TechPress.

Buy it now!

The 500XL Desktop Earbud Speakers are 500 times the size of the stock earbuds that come with iPods but are otherwise identical (though a version old.) While I’m not about to replace my new Klipsch desktop speakers these would look great next to my iMac!

Adam@Home is an often funny comic somewhat like Dilbert, but the main character works from home.

Jolly writes:

Great book!

A well written book. A great way to learn shell scripting. Relevant and useful examples throughout the book (downloadable code).

Thanks for the review Jolly!

For more information like this check out my book Oracle Shell Scripting, only $34.95 from Rampant TechPress.

Buy it now!

To find out what shell you are currently using we can use the echo command:

$ echo $SHELL
/bin/bash

In this command we are using the echo command to examine the value of the environment variable $SHELL. This variable was set by the system when we started this command line session and shows the full path to the shell we were assigned at login. Here are some common shells you might see:

• /bin/sh – Bourne shell
• /bin/bash – Bourne Again shell
• /bin/csh – C shell
• /bin/ksh – Korn shell
• /bin/tcsh – TC shell
• /bin/zsh – Z shell

Shell binaries are also commonly found in the /usr/local/bin directory. Consult your system administrator if you’re having trouble finding your shell binaries.

For more information like this check out my book Oracle Shell Scripting, only $34.95 from Rampant TechPress.

Buy it now!

Sanyo eneloop batteries are a rechargeable NiMH battery which claim to only loose 15% of their charge in a year. That means you can charge them and use them when you need them. Like other NiMH batteries they can be recharged hundreds of times, but one of the big advantages is that they come pre-charged! You could buy a set in a drug store, use them that day, then take them home and recharge them.

I’ve only seen these on Amazon so far, but I’m using them in just about everything I have that takes AA batteries, especially my Wii remotes. At first I was disappointed that the Wii remote didn’t come with a rechargeable battery but now it seems much more clever that they went with an industry standard (AA size) battery which can be easily replaced without having to look up a model number.

Eneloop batteries are available in four packs of AA and AAA and 8 packs of AA, but I recommend starting off with the charging kit which comes with the charger and four AAs. The charger will charge AA and AAA sizes and can charge one, two, three or four batteries at a time.

I have been using these rechargeable batteries for over a year now in my Wii controllers, talkabout radios, remotes, wireless computer accessories and more. They have cut my AA consumption down considerably, and when they do eventually die they are recyclable like other NiMH batteries. While there are AA rechargeables which have a higher capacity the low self-discharge of the Eneloop batteries makes them last longer in all but the highest current applications.