Slides on introduction to shell scripting - RHCSA+

1. Introduction to Shell
Scripting

2. Shell Scripts
Executable file comprising a series of shell commands executed in sequence.
Within the file, you can include:
● Shell declaration (#!/bin/bash)
● Commentary lines (# comments)
● Various commands (echo, cp, grep, etc.)
● Control statements (if, while, for, etc.)
● Ensure executable permissions (e.g., -rwx r-x r-x)
● Call script using absolute path (e.g.,-/home/userdir/script.bash)
● Calling from the current directory, use ./script.bash

3. Getting Started with Shell Scripts
● touch hello.sh - creates an empty text file
● Shebang line (#!/bin/bash) specifies bash as the interpreter for
executing our script commands.

4. ● Shell script structure-combines shebang (#!/bin/bash) and echo
commands to perform tasks, executed using ./scriptname.sh
● chmod +x hello.sh - makes script executable, allowing it to run as a
program

5. Working with Variables and User Input
● Script that collects user input using read variable and displays a
personalized greeting message
● Uses basic commands (read, echo) and variables

6. ● chmod +x user_input.sh -Adds execute permissions to transform the script
into a directly runnable program file.
● ./user_input.sh -Executes the script from the current directory

7. Conditional Statements
● Uses if-else statements to check if a user's number is greater than 10
● Uses basic conditional operators (-gt) and keywords (if, then, else, fi) to make
decisions based on input
● If-Then: Conditional execution of code.
Syntax:
`if [ condition ]; then action; fi`

9. ● chmod +x conditional.sh -Makes the script executable
● ./conditional.sh -Runs the script and verify that it evaluates user input
against the condition, and display appropriate message based on the
number comparison.