Linux Shells

Introduction

# To see which shell you are using
echo $SHELL

# list down the available shells in Linux OS
cat /etc/shells

# make this shell as the default shell for your terminal
chsh -s /usr/bin/zsh

# display all your previous commands
history

Shell Scripting

Components

The file must be named with an extension .sh.

Every script should start from shebang---#!/bin/bash

To give these permissions to the script, we can type the following command in our terminal:

chmod +x variable_script.sh

Variables

variable_script.sh

# Defining the Interpreter 
#!/bin/bash
echo "Hey, what’s your name?"
read name
echo "Welcome, $name"

Loops

loop_script.sh

# Defining the Interpreter 
#!/bin/bash
for i in {1..10};
do
echo $i
done

Conditional Statements

conditional_script.sh

# Defining the Interpreter 
#!/bin/bash
echo "Please enter your name first:"
read name
if [ "$name" = "Stewart" ]; then
        echo "Welcome Stewart! Here is the secret: THM_Script"
else
        echo "Sorry! You are not authorized to access the secret."
fi

常用命令: 介绍一些在脚本中常用的 Linux 命令，例如 if, then, else, for, while, echo, read, sed, awk, grep, find 等。

脚本调试: 讲解如何调试脚本，例如使用 set -x 开启调试模式。