Shell basics

The shell is a command interpreter. It reads input, expands it, executes commands, and manages environment state. Bash and Zsh are the most common.

Core concepts

• Prompt: Shows context like user, host, and current directory.
• Environment variables: Key-value pairs that configure behavior.
• Pipelines: Chain commands using | to pass output into the next command.

Example

export PATH="$HOME/bin:$PATH"
ps aux | grep -i "nginx" | head -n 5