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- Linux Shell Scripting Tutorial Pdf
What is a Shell?
An Operating is made of many components, but its two prime components are -
Shell program is series of Linux commands. Shell script is just like batch file is MS-DOS but have more power than the MS-DOS batch file. Shell script can take input from user, file and output them on screen. Useful to create our own commands that can save our lots. Sep 21, 2019 Shell scripting is writing a series of command for the shell to execute. It can combine lengthy and repetitive sequences of commands into a single and simple script, which can be stored and executed anytime. This reduces the effort required by the end user. Create a file.
- Kernel
- Shell
Bash has become a de facto standard for shell scripting on most flavors of UNIX. Most of the Most of the principles this book covers apply equally well to scripting with other shells, such as the Korn Shell. Her research interests include operating systems and system-side programming. Kennedy has been administering Unix and Linux servers and workstations since 1997. He has experience with Red Hat, SUSE, Ubuntu, Debian, Solaris, and HP-UX. John is also experienced in Bash shell scripting and is currently teaching himself Python and Ruby. Shell Scripting Tutorial. A shell script is a computer program designed to be run by the Unix/Linux shell which could be one of the following: A shell is a command-line interpreter and typical operations performed by shell scripts include file manipulation, program execution, and printing text.
A Kernel is at the nucleus of a computer. It makes the communication between the hardware and software possible. While the Kernel is the innermost part of an operating system, a shell is the outermost one.
A shell in a Linux operating system takes input from you in the form of commands, processes it, and then gives an output. It is the interface through which a user works on the programs, commands, and scripts. A shell is accessed by a terminal which runs it.
When you run the terminal, the Shell issues a command prompt (usually $), where you can type your input, which is then executed when you hit the Enter key. The output or the result is thereafter displayed on the terminal.
The Shell wraps around the delicate interior of an Operating system protecting it from accidental damage. Hence the name Shell.
In this tutorial, you will learn-
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Types of Shell
There are two main shells in Linux:
1. The Bourne Shell: The prompt for this shell is $ and its derivatives are listed below:
- POSIX shell also is known as sh
- Korn Shell also knew as sh
- Bourne Again SHell also knew as bash (most popular)
2.The C shell: The prompt for this shell is %, and its subcategories are:
- C shell also is known as csh
- Tops C shell also is known as tcsh
We will discuss bash shell based shell scripting in this tutorial.
What is Shell Scripting?
Shell scripting is writing a series of command for the shell to execute. It can combine lengthy and repetitive sequences of commands into a single and simple script, which can be stored and executed anytime. This reduces the effort required by the end user.
Let us understand the steps in creating a Shell Script
- Create a fileusing a vi editor(or any other editor). Name script file with extension .sh
- Start the script with #! /bin/sh
- Write some code.
- Save the script file as filename.sh
- For executing the script type bash filename.sh
'#!' is an operator called shebang which directs the script to the interpreter location. So, if we use'#! /bin/sh' the script gets directed to the bourne-shell.
Let's create a small script -
Let's see the steps to create it -
Command 'ls' is executed when we execute the scrip sample.sh file.
Adding shell comments
Commenting is important in any program. In Shell programming, the syntax to add a comment is
Let understand this with an example.
What are Shell Variables?
As discussed earlier, Variables store data in the form of characters and numbers. Similarly, Shell variables are used to store information and they can by the shell only.
For example, the following creates a shell variable and then prints it:
Below is a small script which will use a variable.
Let's understand, the steps to create and execute the script
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As you see, the program picked the value of the variable 'name' as Joy and 'remark' as excellent.
This is a simple script. You can develop advanced scripts which contain conditional statements, loops, and functions. Shell scripting will make your life easy and Linux administration a breeze.
Summary:
Linux Shell Script Programming Pdf
- Kernel is the nucleus of the operating systems, and it communicates between hardware and software
- Shell is a program which interprets user commands through CLI like Terminal
- The Bourne shell and the C shell are the most used shells in Linux
- Shell scripting is writing a series of command for the shell to execute
- Shell variables store the value of a string or a number for the shell to read
- Shell scripting can help you create complex programs containing conditional statements, loops, and functions
- Unix / Linux for Beginners
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A shell script is a computer program designed to be run by the Unix/Linux shell which could be one of the following:
- The Bourne Shell
- The C Shell
- The Korn Shell
- The GNU Bourne-Again Shell
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A shell is a command-line interpreter and typical operations performed by shell scripts include file manipulation, program execution, and printing text.
Extended Shell Scripts
Shell scripts have several required constructs that tell the shell environment what to do and when to do it. Of course, most scripts are more complex than the above one.
Linux Shell Scripting Tutorial Pdf
The shell is, after all, a real programming language, complete with variables, control structures, and so forth. No matter how complicated a script gets, it is still just a list of commands executed sequentially.
The following script uses the read command which takes the input from the keyboard and assigns it as the value of the variable PERSON and finally prints it on STDOUT.
Here is a sample run of the script −
Subsequent part of this tutorial will cover Unix/Linux Shell Scripting in detail.