Permissions, Redirection and Piping

Now that you can move around and manage files, it’s time to learn how to
control who can do what to those files, and how to connect commands
together to do more powerful things than any single command can do on its
own.

Why This Matters

“Permission denied” errors are one of the most common things you’ll run
into in Terminal, and understanding permissions, users, and groups is
what lets you fix them confidently instead of just reaching for sudo
and hoping. Redirection and piping, meanwhile, are what turn Terminal
from “a place to type isolated commands” into “a place to build small
pipelines” — which is most of what real command-line work looks like.

What You’ll Learn

• How to read and change file permissions with chmod, and ownership
  with chown and chgrp
• What root and sudo are, and when you need them
• How to create hard and symbolic links
• How to send command output to a file with > and >>, and read input
  from a file with <
• How to chain commands together with |, using tools like head,
  tail, sort, uniq, wc, and grep

Outcome

By the end of this module, you’ll be able to manage permissions
confidently and combine commands into pipelines to solve problems no
single command can handle alone.

Let’s dig in.