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Introduction To Variables

The document provides an introduction to variables in Bash shell scripting, explaining their importance for storing data. It distinguishes between system variables, which are predefined by the operating system, and user-defined variables, which are created by the user following specific naming rules. Additionally, it outlines the rules for defining user-defined variables, including naming conventions and how to assign values.

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17 views4 pages

Introduction To Variables

The document provides an introduction to variables in Bash shell scripting, explaining their importance for storing data. It distinguishes between system variables, which are predefined by the operating system, and user-defined variables, which are created by the user following specific naming rules. Additionally, it outlines the rules for defining user-defined variables, including naming conventions and how to assign values.

Uploaded by

varun186
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Variables

NarendraP

Learn How to Automate Common Tasks with Bash Shell Scripting


Introduction to Variables
 Variables are useful to store data in shell scripts and Later we can use them if they required.
 Simple Variable: x=4
 Default value of a variable is Empty/Nothing
 In Linux Shell Scripting, there are two types of variables:
 System Variables:
 Created and maintained by Operating System itself.
 This type of variables are defined in CAPITAL LETTERS.
 We can see them by using set command
 Example: HOME, USER…
 User Defined Variables:
 Created and maintained by the user.
 This type of variables are defined in lower letters.
 But we can also take combination of upper and lower case letters.

Learn How to Automate Common Tasks with Bash Shell Scripting


Rules to Define User Defined Variables
 Variable Name should contain only a-z or A-Z, 0-9 and _ characters.
 Variable Name length should be less than or equal to 20 characters.
 Variable Names are case sensitive. Means x and X are different.
 Don’t Provide space on either sides of equal symbol while defining variables
 Ex: x=4 is valid
 x =4 or x = 4 or x= 4 are invalid
 No need to declare variable type, Automatically it will take care while executing commands or scripts.
 Use quotes for the data if data consist of spaces
 We can store the output of a command into a variable as follows:
 anyVariable=$(command)
 anyVariable=`command`
 We can assign one variable value/data into another using:
 Name=“Shell Scripting”
 NewName=$Name
 NewName=${Name}

Learn How to Automate Common Tasks with Bash Shell Scripting


Thank you

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