Shell

Variables

All active variables can be seen by running env.

• $HOME - Expands to the path of my home folder.

• $PS1 - Variable that represents my command prompt line.

• $PATH - Special environment variable that contains the command path (list of system directories that the shell searches when trying to locate a command).

Notes

• Scripts are run in subshells, and nothing is shared "upwards". That's the difference between running a script and sourcing one. A sourced (imported) script is run in your own script's namespace.

• In shell everything is a string.

• Children never touch parent environment. It can only if it runs as part of the current process (source, function, alias).

• Pipes are used to connect one process's output with another process’s input.

• /etc/paths.d define paths to add to $PATH globally to all users.

Links

• Explain Shell

• Introduction to POSIX Shell

• Yoshua's notes

• Shell Auto-completion Systems

• Shell and Scripting (2019)

• ShellCheck - Finds bugs in your shell scripts.

• Rash - The Reckless Racket Shell.

• Eternal Terminal - Remote shell that automatically reconnects without interrupting the session.