The Linux Juggernaut

 Redirecting operators in Linux

 In order to understand about Redirecting operators in Linux we should know how we communicate with a computer. When we are communicating with a computer there should be a way to do it and this is achieved by STDIN (0), STDOUT (1), STDERR (2) file descriptors. There are numbers assigned to these file descriptors as shown below.

STDIN --> 0 
STDOUT  --> 1 
STDERR --> 2

We will see what … Continue Reading

Debugging a shell script is very essential to check your script for any errors before moving in to production. In this post we will see different debugging tips and tricks useful for running your scripts without a flaw.

Before debugging a script we have to learn how to write a shell script professionally in order to minimize the errors.

 When executing a shell script use sh command with below options to debug a shell script … Continue Reading

There are many shell inbuilt variables which are used for administrating and writing shell scripts. In this post we will see important inbuilt variables and their importance. Please add any other built-ins which are useful for administration and for shell scripting.

Note: in order get present values of these variables use echo command to get them. For example if you want to see present shell then you can give echo $SHELL to get the … Continue Reading

How to write a shell script professionally and why to write it?

Most of the time when we work and write shell script we write on the go not considering others who want to understand it. Suppose you write a shell script and did not given any info what that shell script do, all your efforts will be in vain if a new system admin is unable to understand it. We have to make a … Continue Reading

This is a small how-to topic on running the shell script you just received or created. The basic philosophy of Linux is to consider everything as files. And if you want to execute a file/app the permissions are set to executable on that file otherwise you will get permissions denied.

Let’s try to execute a script without setting executable permissions to the shell script file and see what happens?.

./numper.sh bash: ./numper.sh: Permission denied

So … Continue Reading

Regular expressions (Regexp)is one of the advanced concept we require for writing efficient shell scripts. We divided regular expressions in to 3 types for better understanding.

1)Basic Regular expressions
2)Interval Regular expressions
3)Extended Regular expressions(Use option -E for grep and -r for sed)

Basic regular expressions: The set includes very basic set of regular expressions which do not require any options to execute.

Which commands support regular expressions?
tr, grep, sed, awk etc.… Continue Reading