Process & Threads

Processes

A process is an independent program in execution.

• Has its own memory space
• Runs separately from other processes
• Example: Opening Chrome creates a new process

Threads

A thread is a smaller unit of execution inside a process.

• Shares memory with other threads in the same process
• Lightweight and faster to create
• Example: Multiple tabs running inside one app process

Key Differences

• Memory
  • Process → Separate memory
  • Thread → Shared memory
• Communication
  • Process → Slower (IPC needed)
  • Thread → Faster (shared data)
• Overhead
  • Process → Heavy
  • Thread → Lightweight
• Crash Impact
  • Process → Isolated (safer)
  • Thread → Can crash entire process

Real-World Analogy

1. Process = Building
2. Threads = People working inside it

• Different buildings don’t share rooms (process isolation)
• People inside can easily share resources (threads)

Why It Matters

• Impacts performance & scalability
• Crucial for:
  • Backend systems
  • Multithreading
  • Parallel processing
  • High-performance apps

Pro Tip :)

• Use processes for isolation & safety, threads for speed & efficiency.

echo $PATH

echo is used to display text or variables in the terminal.

Basic Usage

echo "Hello World"

Common uses

1. Print variables:

echo $HOME

2. Add text to a file:

echo "Hello" >> file.txt

3. Debug scripts:

echo "Step 1 completed"

Pro tip :)

• echo is your simplest debugging tool — fast, direct, and always available.

Bash files - .bash/.bashrc/.bashprofile

Bash or any shell uses config files to set up your shell environment every time it starts.

• Aliases
• Environment variables
• PATH updates
• Custom scripts

Key Bash files

1. .bashrc

• Runs on every interactive shell
• Best for:
  • Aliases (alias ll="ls -l")
  • Functions
  • Prompt customization
• Most commonly used file

2. .bash_profile

• Runs on login shells (when you log in)
• Best for:
  • Environment variables
  • Startup programs
• Often calls .bashrc inside it

3. .profile

• More generic version (works beyond bash)
• Used if .bash_profile is missing

Pro tip :)

Treat your .bashrc like your dev setup script — version it, refine it, own it.

Aliases

An alias is a shortcut for a longer command. It makes your life easy

• Saves time + reduces typing

Basic Usage

alias ll="ls -l"

• Now instead of typing ls -l, just type:

ll

Common Examples

1. Safer delete:

alias rm="rm -i"

2. Human-readable listing:

alias lh="ls -lh"

3. Git shortcuts:

alias gs="git status"
alias gc="git commit"

Make Them Permanent (if you want to)

Add them to:

• .bashrc (Bash)
• .zshrc (Zsh)

Then reload:

source ~/.bashrc

View & Remove Aliases

1. List all:

alias

2. Remove:

unalias ll

Pro tip :)

• Aliases turn your terminal into a personalized toolkit — optimized for how you work.

--

export command

export is used to set environment variables and make them available to child processes.

• Without export, variables stay local to the current shell.

Basic Usage

export NAME="value"

Why export matters

Used for:

• API keys
• Config values
• System paths
• App settings

Example -

export NODE_ENV="production"

Without vs With Export

• Without export:

MY_VAR="hello"

Not visible to child processes

• With export:

export MY_VAR="hello"

Accessible everywhere (child processes)

Main concept

• export moves a variable from shell scope → environment scope

Pro tip

• Environment variables are inherited downward (parent → child)
• Not upward

pwd (Present working directory)

pwd stands for print working directory — it shows your current location in the filesystem.

Basic Usage

pwd

• Outputs the full path of your current directory

Output example -

/home/user/projects/my-app

Why it matters

• Helps you stay oriented in the terminal
• Essential when navigating deep folder structures
• Useful in scripts and debugging

Pro tip :)

• If you're lost in the terminal, pwd is your GPS.

. -> current & . -> parent

• . -> current directory
• .. -> parent directory (one level up)

Examples

cd .

• Stay in the same directory (useful in scripts)

cd ..

• Move one level up

Pro tip

• . keeps you grounded, .. moves you upward — master both to navigate effortlessly.

Well, that's it for today guys. I hope you have learnt something valuable.

See you Tomorrow. Feel free to reach out to me in case if you need any help.