Master Essential Linux Commands in 8 Minutes: A Quick Cheat Sheet

1. ls – similar to the DOS dir command. Frequently used options are -a, -l, and -F. -a shows hidden files (those beginning with a dot). -l displays detailed file information. -F appends symbols to indicate file types (e.g., * for executables, / for directories, @ for links).

2. cd – changes the current working directory. Examples: cd aaa enters directory aaa; cd or cd ~ returns to the user’s home directory; cd - goes back to the previous directory; cd .. moves up one level.

3. pwd – prints the current working directory.

4. mkdir and rmdir – mkdir creates directories, rmdir removes empty directories. Both support the -p option: mkdir -p 1/2/3 creates the whole path, while rmdir -p 1/2/3 removes nested empty directories.

5. cp – copies files or directories. Examples: cp 1.txt ../test2 copies a file to another directory; cp 1.txt 2.txt copies and renames; cp -r a b copies directory a to b.

6. mv – moves or renames files. Examples: mv 1.txt ../test1 moves a file; mv 1.txt 2.txt renames a file; mv 1.txt ../test1/2.txt moves and renames simultaneously.

7. rm – deletes files. Common options: -i (prompt before deletion), -r (recursive, also removes directories), -f (force, no prompt). Deletions are irreversible.

8. du and df – du shows disk space used by directories; df shows available disk space. du -hs ./* lists sizes of all items in the current directory. Options -k, -m, and -h control units (kilobytes, megabytes, human‑readable).

9. cat – concatenates and displays file contents. Examples: cat file1, cat file1 file2, cat file1 file2 > file3. Redirection symbols > (overwrite) and >> (append) control output.

10. echo – prints strings to standard output, often used in scripts. Syntax: echo [-ne] [string]. Options: -n (no trailing newline), -e (enable escape sequences such as \n, \t, etc.).

11. more, less, clear – more and less paginate long file output; less allows scrolling with arrow keys. clear clears the terminal screen, analogous to DOS cls.

12. head and tail – head shows the first n lines of a file, tail shows the last n lines (default 10). Use -n to specify a different count, e.g., head -100 file. tail -f follows a file in real time.

13. wc – counts lines ( -l), words ( -w), and bytes ( -c) in files. Options can be combined; output order follows the option order.

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

15. man and logout – man displays the manual page for a command (e.g., man ls). logout exits the current shell session.

16. Pipes and xargs – the pipe symbol | passes the output of one command as input to another (e.g., ls | grep a). xargs builds command lines from standard input, useful for handling large argument lists (e.g., ls | xargs rm).

17. basename and 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 (without arguments) – displays all shell variables and functions.