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shell

Shell User Manual​

This guide provides a detailed explanation of basic and advanced techniques for using the Bash shell. Additionally, it covers some features of Zsh. A shell is a program used to operate the command-line interface, commonly used for system administration and scripting.

Table of Contents​

Shell Basics​

Starting the Shell​

Open a terminal (or command prompt) to start the shell. By default, Bash is usually started.

bash

Basic Commands​

Below are frequently used basic commands in Bash.

  • ls: Displays the contents of a directory. 
    ls
  • cd: Changes the current directory. 
    cd /path/to/directory
  • pwd: Prints the current directory. 
    pwd
  • echo: Outputs text. 
    echo "Hello, World!"
  • cat: Displays the contents of a file. 
    cat file.txt

Bash Basics​

Using Variables​

Learn how to define and use variables in Bash.

Defining and Using Variables​

name="Alice"
echo $name

Environment Variables​

export PATH=$PATH:/new/path

Control Structures​

Control structures in Bash include if statements, for loops, and while loops.

If Statements​

if [ condition ]; then
    echo "Condition is true"
else
    echo "Condition is false"
fi

For Loops​

for i in 1 2 3; do
    echo "Number $i"
done

While Loops​

count=1
while [ $count -le 5 ]; do
    echo "Count: $count"
    count=$((count + 1))
done

Defining Functions​

Learn how to define and use functions in Bash.

my_function() {
    echo "Hello, $1"
}

my_function "Alice"

Advanced Bash Usage​

Regular Expressions and Pattern Matching​

Using regular expressions and pattern matching in Bash.

if [[ "hello" =~ ^h.*o$ ]]; then
    echo "Matches"
fi

Creating Shell Scripts​

How to create and execute shell scripts.

#!/bin/bash
echo "This is a shell script"

Give the script execute permission and run it.

chmod +x script.sh
./script.sh

Job Management​

Manage jobs in Bash.

Background Jobs​

sleep 10 &

Bringing Jobs to Foreground​

fg %1

Input/Output Redirection​

Learn how to use input/output redirection in Bash.

Redirecting Standard Output​

echo "Hello, World!" > output.txt

Redirecting Standard Error​

ls /nonexistent 2> error.txt

Redirecting Both Standard Output and Error​

command > output.txt 2>&1

Introduction to Zsh​

Installing Zsh​

How to install Zsh.

On macOS​

brew install zsh

On Ubuntu​

sudo apt-get install zsh

Basic and Advanced Features​

An overview of Zsh’s basic and extended functionalities.

Autocompletion​

How to enable Zsh’s powerful autocompletion.

autoload -Uz compinit
compinit

Using Oh My Zsh​

Customize Zsh using Oh My Zsh.

sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"

Advanced Shell Operations​

Process Substitution​

Using process substitution.

diff <(ls dir1) <(ls dir2)

Aliases and Shell Customization​

Create aliases and customize the shell in Bash or Zsh.

Creating Aliases​

alias ll='ls -la'

Customizing the Shell Prompt​

export PS1="\u@\h \W> "

Command History Manipulation​

How to work with command history in Bash or Zsh.

Viewing History​

history

Re-running Specific Commands​

!42

Searching History​

Ctrl + r

This concludes the explanation of basic and advanced shell usage in Bash and Zsh. Shells are powerful and flexible tools, and understanding their features is key to using them efficiently.