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Lab 2

This document provides information about shell scripts including: - Shell scripts allow automation of tasks through a series of commands written in plain text. They have more power than batch files in MS-DOS. - Reasons for writing shell scripts include taking user input/output, creating custom commands, automation, and system administration tasks. - Shell scripts can be written in any text editor and made executable by setting permissions through graphical or command line interfaces. - The document demonstrates simple shell scripts and discusses variables in shell scripts including system, user defined, and parametric variables.

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SyEda SamReen
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25 views11 pages

Lab 2

This document provides information about shell scripts including: - Shell scripts allow automation of tasks through a series of commands written in plain text. They have more power than batch files in MS-DOS. - Reasons for writing shell scripts include taking user input/output, creating custom commands, automation, and system administration tasks. - Shell scripts can be written in any text editor and made executable by setting permissions through graphical or command line interfaces. - The document demonstrates simple shell scripts and discusses variables in shell scripts including system, user defined, and parametric variables.

Uploaded by

SyEda SamReen
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Operating Systems

Lab 02
Shell Scripts
Lab Instructor: Zainab Iftikhar
Shell Scripting
Shell Scripting

Shell Script is series of command written in plain


text file. Shell script is just like batch file is MS-DOS but
have more power than the MS-DOS batch file."
 Why to write shell scripts?
o Shell script can take input from user, file and output them
on screen.
o Useful to create our own commands.
o Save lots of time.
o To automate some task of day today life.
o System Administration part can be also automated.
How to write shell scripts

 Use any editor to write shell script


 Set the execute permission for your script through
o Graphical interface
o chmod +x script-name
o chmod 755 script-name
My First Shell Script
Code:
Save the file as s1.sh in Home

Output:
My Second Shell Script
Code:

Save the file as s1.sh in Home


Commands to run on terminal

Output:
Variables in Shell

 In Linux shell there are three types of variables


System variables
User defined variables
Parametric variables
User Defined Variables

 Rules for defining variables


o Name must start with an alphanumeric character
o Can use underscore in between the characters
o Don't put spaces on either side of the equal sign
when assigning value to variable
 var=10
o NULLvariable declaration
 var=
 var=“”
 Do not use ?,* to name your variable names
User Defined Variables

 Defining user variables


o no=10
o Variable „no‟ is assigned value 10

 Accessing/printing variables
o Toaccess variables use „$‟
o echo $no
User Defined Variables Example
Code:

Output:

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