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Hello Shell:

A shell is a command-line interpreter that allows you to interact with your computer's operating system by typing in commands. Essentially, it acts as an intermediary between you and the operating system kernel.

Types of Shell:

Just like there are different operating systems (Windows, macOS, Linux), there are different shells with varying features and strengths. Here are a few popular ones:  

Bash (Bourne Again Shell) This is the most common shell on Linux and macOS systems; known for its wide range of features, scripting capabilities.

Zsh (Z Shell) Built upon Bash, offering enhanced features like plugins, themes, and improved auto-completion and

Others PowerShell, Fish etc.

Common Uses:

System administration Managing users, configuring network settings, automating system maintenance tasks.  

Software development Compiling code, running tests, managing version control systems.

Data analysis Processing and analyzing large datasets, running statistical models.

Everyday tasks Managing files, Auromation etc.

Some magical Tools (Mac specific):

These are the tools that I install when I get a new mac. Get the latest versions from the official documents.

iTerm Supercharged version of terminal the Mac default terminal. Helps split panes.

Homebrew Mac (also Linux) package manager. Most tools, libraries can now be installed with a simple brew install <my_tool> and it's a picnic to update anything.

Zsh Only to get some cute cat themes for my terminal!

Tmux Kind of like create different panes on one screen. Helps create persistent sessions, remote server management etc.

Top Shell Commands

Navigation:

  • pwd : Print Working Directory - shows your current location.
  • cd : Change Directory.
    • cd .. : Move up one level.
    • cd / : Move to the root directory.
    • cd ~ : Move to your home directory.
  • ls : List Directory contents.
    • ls -l : Long listing format (more details).
    • ls -a : List all files, including hidden ones.

File Management:

  • touch <filename> : Create an empty file.
  • mkdir <directoryname> : Create a new directory.
  • cp <source> <destination> : Copy files and directories.
  • mv <source> <destination> : Move or rename files and directories.
  • rm <filename> : Remove files and directories.
    • rm -r <directoryname> : Remove directories recursively.
    • rm -f <filename> : Force removal without prompting (use with caution!).
  • diff <file1> <file2> : Differences between 2 files

System Information:

  • uname : Display system information (kernel name, version, etc.).
  • df : Disk Free - shows disk space usage.
  • du : Disk Usage - shows file and directory space usage.
  • top : Display real-time system processes.
  • free : Display memory usage.

Process Management:

  • ps : List running processes.
  • kill <processID> : Terminate a process.
  • jobs : List background jobs.
  • fg : Bring a background job to the foreground.
  • bg : Run a job in the background.

Other Essentials:

  • man <command> : Manual - display the help page for a command.
  • grep <pattern> <filename> : Search for a pattern in a file.
  • history : List your recent commands.
  • history | grep <term> : Recent commands containing the term.
  • find <directory> -name <filename> : Locate files.
  • rg <searchterm> : Recursive golbal search for a term. (Needs an install).
  • chmod <permissions> <filename> : Change file permissions.
  • chown <user>:<group> <filename> : Change file ownership.
  • | (pipe) : Redirect output of one command to another.
  • > : Redirect output to a file (overwrites existing content).
  • >> : Append output to a file.
  • < : Redirect input from a file.

How to Create a Bash script

Bash scripting is a powerful way to automate tasks on Linux and macOS systems. Here's a step-by-step guide to get you started:

1. Create a new file

Use a text editor to create a new file. You can name it anything you like, but it's common to use a .sh extension (e.g., my_script.sh).

2. Add the shebang

The first line of your script should be the shebang: #!/bin/bash This tells the system to use the Bash interpreter to execute the script.

3. Write your commands

Add the commands you want to execute, one per line. For example:

#!/bin/bash

echo "Hello, world!"
date
ls -l

4. Make the script executable

Use the chmod command for this chmod +x my_script.sh

5. Run the script

./my_script.sh