The Day-to-day Toolkit

These commands are the verbs of the Linux shell. Mastering them is mastering productivity.

Location & Navigation

• pwd — print working directory.
• cd path — change directory. Special targets: cd ~ (home), cd - (previous), cd .. (parent), cd / (root).
• ls — list. Common flags: -l long, -a hidden, -h human sizes, -t time order, -R recursive.

Inspecting Files

• cat file — concatenate / show.
• file name — guesses the file type by inspecting its magic bytes.
• echo "text" — print text or variables.

Creating & Removing

• mkdir dir — create a directory; -p creates parents.
• rmdir dir — remove an empty directory.
• rm file — delete; -r recursive, -f force, -i interactive.
• cp src dst — copy; -r recursive, -i prompt before overwrite, -v verbose.
• mv src dst — move/rename.

Calculator & Date

• bc — arbitrary-precision calculator. Use -l for math library.
• date — current date/time; +%Y-%m-%d for custom formats.
• cal — print a calendar.

System Identity

Aliases — Personalize the Shell

alias creates a shorthand for a longer command. Add to ~/.bashrc to make it permanent:

alias ll='ls -lah'

Remove with unalias ll.

Worked Example: Build a Project Tree

Suppose we want a directory layout for a course project:

1. mkdir -p ~/proj/src ~/proj/docs ~/proj/tests
2. cd ~/proj && pwd confirms /home/you/proj.
3. echo "# Hello" > docs/README.md
4. ls -lR shows the whole tree with permissions and sizes.

Summary

• pwd / cd / ls are the spatial trio.
• cp, mv, rm, mkdir are the file verbs — combine with -i to stay safe.
• who, whoami, uname, hostname answer "who and where am I".