Chapter 5: Bash Commands

Bash commands are the words/phrases you type in the terminal that Bash understands and executes. Almost everything you do in Bash is running one (or many) of these commands.

There are hundreds of commands, but today we’ll focus on the 30–35 most important ones for beginners to intermediate level — the ones you’ll use 90% of the time in real life (Hyderabad developer, server work, automation, etc.).

We’ll group them nicely, explain what, why, how, common options, examples, and little warnings from your friendly teacher.

Group 1: Navigation & Orientation (You use these 100 times a day)

1. pwd — Print Working Directory Where am I right now?
   Bash

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   pwd

   → /home/webliance/projects/myapp

2. ls — List Show what’s in current folder
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   ls               # simple list ls -l            # long format (permissions, size, date) ls -la           # show hidden files (start with .) ls -lah          # human-readable sizes (KB, MB) ls -l --color=auto  # colored output (most terminals do auto) ls *.jpg         # only jpg files

3. cd — Change Directory Move around
   Bash

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   cd myfolder          # go inside cd ..                # one level up cd ~                 # or just cd → go home cd /etc              # absolute path cd ~/Downloads       # home + relative cd -                 # back to previous location

Group 2: Creating & Viewing Stuff

4. mkdir — Make Directory
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   mkdir new_project mkdir -p parent/child/grand   # create full path if missing

5. touch — Create empty file or update timestamp
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   touch notes.txt report.md touch file{1..5}.txt          # creates file1.txt to file5.txt

6. echo — Print text (also writes to files)
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   echo "Hello Hyderabad!" echo "Line 1" > file.txt      # overwrite echo "Line 2" >> file.txt     # append echo $PATH                    # show variable

7. cat — Concatenate / show file content
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   cat readme.md cat file1.txt file2.txt > combined.txt cat > newfile.txt             # type until Ctrl+D

8. less / more — View large files page by page
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   less long_log.txt    # arrow keys, / to search, q to quit more access.log      # simpler version

Group 3: Copy, Move, Rename, Delete (Be careful!)

9. cp — Copy

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   cp source.txt dest.txt cp -r folder1 backup_folder   # recursive for folders cp *.png ~/Pictures/ cp -i file.txt dest/          # ask before overwrite

10. mv — Move / Rename

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    mv oldname.txt newname.txt     # rename mv file.txt ../other_folder/ mv -i important.txt backup/    # safe (asks)

11. rm — Remove (no recycle bin — gone forever!)

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    rm temp.txt rm -r old_project/             # delete folder + contents rm -rf node_modules/           # force, dangerous! rm -i *.tmp                    # ask for each file

    Teacher golden rule: Always use -i when learning. Never rm -rf / (it can destroy your system!)

12. rmdir — Remove empty directory

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    rmdir empty_folder

Group 4: Finding & Searching

13. find — Search for files
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    find . -name "*.log"           # in current folder find /home -type f -size +100M # big files >100MB find . -mtime -7               # modified last 7 days

14. grep — Search inside text
    Bash

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    grep "error" server.log grep -i "todo" *.md            # case insensitive grep -r "function" .           # recursive in all files grep -n "bug" app.js           # show line numbers

15. which / whereis / type
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    which python          # where is the command located? type ls               # is it alias, builtin, or external?

Group 5: System Info & Help

16. date
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    date date +"%Y-%m-%d %H:%M:%S"   # custom format

17. whoami / id
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    whoami     # your username id -un     # same

18. df -h — Disk free (human readable)
    Bash

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    df -h

19. du -sh — Disk usage
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    du -sh ~/Downloads     # how big is Downloads? du -sh * | sort -h     # sort folders by size

20. free -h — Memory usage
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    free -h

21. top / htop — Live processes (htop is nicer if installed)
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    top

22. man — Manual (best help!)
    Bash

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    man ls man cp     # press q to quit

23. –help — Quick help
    Bash

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    ls --help

Group 6: Power User Basics (You’ll love these soon)

24. history — See past commands
    Bash

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    history | tail -20 !123           # run command number 123 from history

25. clear — Clear screen
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    clear Ctrl + L       # same (shortcut)

26. alias — Create shortcuts
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    alias ll='ls -la' alias update='sudo apt update && sudo apt upgrade -y' # Put in ~/.bashrc to keep forever

27. uname -a — System info
    Bash

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    uname -a

28. ps aux — List processes
    Bash

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    ps aux | grep chrome

29. kill — Stop process
    Bash

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    kill 1234      # PID from ps kill -9 5678   # force kill

30. sudo — Run as superuser
    Bash

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    sudo apt update

Quick Cheat Table (Save this!)

Practice right now — open terminal:

Tell me what output you got or if any command gave error — we’ll debug together!

Next class? Say: “Teacher, explain pipes and redirection” “More on grep and find” “Show 10 real mini-scripts using these commands” “File permissions (chmod, chown)”

You’re getting faster every day — keep practicing! 🐧💪 From sunny Hyderabad! 😊