1. File & Directory Commands

These are the foundational commands for navigating and managing the file system.

1. ls: Lists files and directories. ls -l shows a long-format list with permissions.

   • Example: ls -la to show all files, including hidden ones, in a long list.

   

2. cd: Changes the current directory. cd .. moves up one level. cd ~ goes to the home directory.

   • Example: cd /var/www/html to navigate to a web server's root directory.

   

3. pwd: Prints the full path of the current working directory.

   • Example: pwd will output something like /home/user/documents.

4. mkdir: Creates a new directory.

   • Example: mkdir -p projects/new_project creates a directory and its parent directory if they don't exist.

5. rmdir: Removes an empty directory.

   • Example: rmdir old_folder.

6. touch: Creates a new, empty file or updates the timestamp of an existing file.

   • Example: touch report.txt.

7. cp: Copies files or directories.

   • Example: cp -r /source/dir /destination/ copies a directory recursively.

8. mv: Moves or renames a file or directory.

   • Example: mv old_file.txt new_file.txt.

9. rm: Removes (deletes) files or directories. rm -rf is a powerful and dangerous command to force-delete a directory and its contents recursively.

   • Example: rm config.conf.

10. find: Searches for files in a directory hierarchy.

    • Example: find . -name "*.log" finds all files ending with .log in the current directory.

2. File Content & Editing

These commands are for viewing and modifying the content of files.

1. cat: Concatenates and displays file content. It's often used to quickly view small files.
   • Example: cat file1.txt file2.txt > combined.txt.
2. less: A file pager that lets you view file content one screen at a time, allowing you to scroll both up and down.
   • Example: less big_log_file.log.
3. more: Similar to less, but with more limited scrolling functionality (typically only scrolls forward).
   • Example: more README.md.
4. head: Displays the first 10 lines of a file by default.
   • Example: head -n 5 data.csv to see the first 5 lines.