Shell Tips !

I use math in bash scripts a lot, from simple crontab reports to Nagios monitoring plugins… Here is few small examples on how to do some maths in Bash with integers or float.

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My previous post was made a long time ago, so here is a draft that I finally decide to post. Let’s see how to secure some of your data with an encrypted block device using losetup and dd.

Steps will be :

1. Create an image with dd
2. Build a new device using the image with an encrypt algorythm by using losetup
3. Format the device using mkfs.ext3
4. Mount the device and start using it !

Of course, when you have mounted the device, your data are readable to anyone who have access to the mounted directory.

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Some times, while scripting in your favorite shell (I mean Bash !! :) you need to print a sequence of letters or numbers. Don’t write it yourself ! Script it using seq or curly braces !

Print a sequence of number

nicolas@macvin:~$ seq 1 10
1 2 3 4 5 6 7 8 9 10
nicolas@macvin:~$ seq 0 2 10
0 2 4 6 8 10
nicolas@macvin:~$ echo {1..10}
1 2 3 4 5 6 7 8 9 10

Print a sequence of letters

nicolas@macvin:~$ echo {a..g}
a b c d e f g

Hope this will help you while doing a loop or building some hash directories :

nicolas@macvin:~$  mkdir -p test/{1..10}/{1..10}

Enjoy !