Master Essential Linux Commands: From ls to xargs in 8 Minutes

Essential Linux Commands Overview

1. ls – list directory contents, similar to Windows dir. Common options: -a (show hidden files), -l (detailed list), -F (append file‑type symbols).

2. cd – change the current directory. Examples: cd aaa (enter aaa), cd or cd ~ (go to home), cd - (return to previous directory), cd .. (up one level).

3. pwd – display the present working directory.

4. mkdir & rmdir – create and remove directories. Both support -p to create parent directories or remove a directory tree. Example: mkdir -p 1/2/3, rmdir -p 1/2/3.

5. cp – copy files or directories. Examples: cp 1.txt ../test2 (copy to another directory), cp 1.txt 2.txt (copy and rename), cp -r a b (copy directory a to b).

6. mv – move or rename files. Examples: mv 1.txt ../test1, mv 1.txt 2.txt, mv 1.txt ../test1/2.txt.

7. rm – delete files. Common options: -i (prompt before each removal), -r (recursive, also removes directories), -f (force, no prompt).

8. du & df – du shows disk usage of files/directories; df shows free space on filesystems. Useful forms: du -hs ./* (human‑readable sizes of all items), df -h (human‑readable free space).

9. cat – concatenate and display file contents. Examples: cat file1, cat file1 file2, cat file1 file2 > file3 (redirect output), cat >file1 (type input until Ctrl+D).

10. echo – output strings to the terminal. Syntax: echo [-ne] [string]. Options: -n (no trailing newline), -e (enable backslash escapes). Common escapes: \a (alert), \b (backspace), \n (newline), \t (tab), etc.

11. more, less, clear – paging utilities. more pauses after each screen; less allows forward/backward navigation with keys (e.g., Space, b, g, G, /pattern, q). clear clears the terminal (equivalent to Windows cls).

12. head & tail – view the beginning or end of a file. Default 10 lines; specify number with -n (e.g., head -100 file, tail -100 file). tail -f follows a file in real time.

13. wc – word count. Options: -l (lines), -w (words), -c (bytes). Example: wc -l 1.txt.

14. grep – search files for patterns using regular expressions. Returns matching lines and exit status (0 = match, 1 = no match, 2 = error). Example: ls -l | grep '^a' shows entries starting with “a”.

15. man & logout – man displays manual pages for commands (e.g., man ls); logout exits the current shell session.

16. Pipelines & xargs – the pipe | passes output of one command as input to the next (e.g., ls | grep a). xargs builds command lines from standard input, useful for handling large argument lists (e.g., find / -name "core" -print | xargs echo > /tmp/core.log, ls | xargs rm).

17. basename & dirname – basename extracts the filename without its path; dirname extracts the directory path. Examples: basename /home/hj/1.txt → 1.txt, dirname /home/hj/1.txt → /home/hj.

18. set (no arguments) – displays all shell variables and functions.