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2.4 Shell, Environment, and I/O Basics

The Shell:

The shell interprets commands, often using bash.

  • Structure: command [options] [arguments]
  • Example: ls -l /home

Environment Variables:

echo $HOME
echo $PATH
printenv

PATH determines where the shell looks for commands.

Input/Output:

  • stdout → Normal output
  • stderr → Errors
  • stdin → Input

Redirecting & Piping:

ls > files.txt         # Redirect output
ls /bad 2> errors.txt  # Redirect errors
ls | grep ".txt"       # Pipe into another command