Shell environment preview

Every command inherits an environment: variables like PATH, the current working directory, open file descriptors, and shell options. Understanding the environment prevents “command not found” and permission surprises.

Key environment pieces

• PATH — directories searched for executables
• HOME — your home directory
• PWD — present working directory (maintained by the shell)
• USER / LOGNAME — account identity

Inspecting the environment

echo "Home: $HOME"
echo "Path: $PATH"
printenv | head
which bash
which git

which searches PATH. If Git lessons fail, compare with Git intro install steps in Tools.

Startup files

Login shells read profile files (/etc/profile, ~/.bash_profile). Interactive shells may read ~/.bashrc. Distros differ—when something works in one terminal but not another, compare which file ran.

Important interview questions and answers

1. Q: What does PATH control?
   A: Which directories are searched, in order, when you type a command name without a full path.
2. Q: printenv vs env?
   A: Both list environment variables; env can also run a command with a modified environment.

Self-check

1. Which variable holds your home directory path?
2. What command shows where the bash executable lives?

Tip: If command not found appears, echo $PATH and compare with Tools install docs.