Basics Questions

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Level: Basics

🟢 Foundational interview questions.

Focus on core concepts, definitions, and building blocks.

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??? question "1. Which command prints the current working directory?" pwd (Print Working Directory).

This command displays the full absolute path of the directory you are currently in.

??? question "2. Which command lists files in the current directory?" ls.

`ls` lists the files and directories in the current working directory. `ls -l` shows detailed info, and `ls -a` shows hidden files.

??? question "3. How do you recognize a hidden file in Linux?" It starts with a dot (.).

Files like `.bashrc` or `.gitignore` are hidden by default and won't show up in a standard `ls` unless you use `ls -a`.

??? question "4. Which command is used to change directories?" cd [directory-path].

For example, `cd /var/log` moves you into the `/var/log` directory.

??? question "5. What does cd .. do?" Moves you up one level to the parent directory.

The `..` symbol represents the parent directory.

??? question "6. Which command creates a new directory?" mkdir [directory-name].

Use `mkdir -p a/b/c` to create nested directories (parents) automatically.

??? question "7. Which command creates an empty file?" touch [filename].

If the file already exists, `touch` updates its access and modification timestamps without changing the content.

??? question "8. Which command removes a file?" rm [filename].

To remove a directory and its contents recursively, use `rm -rf [directory-name]`.

??? question "9. Which command copies files or directories?" cp [source] [destination].

To copy a directory, you must use the recursive flag: `cp -r`.

??? question "10. Which command moves or renames files?" mv [source] [destination].

It is used for both moving files to a new location and renaming them (e.g., `mv old.txt new.txt`).

??? question "11. Which command displays the contents of a file?" cat [filename].

It dumps the entire content of the file to the terminal. For larger files, `less` or `more` is often preferred.

??? question "12. Which permission allows executing a file?" x (Execute).

In numeric mode, this corresponds to `1`. It allows a file to be run as a program or script.

??? question "13. What does chmod 755 mean?" Owner has full access (7); Group and Others have read/execute (5).

*   **7** = `rwx` (Read(4) + Write(2) + Execute(1))
*   **5** = `r-x` (Read(4) + Execute(1))

??? question "14. Which command changes file ownership?" chown [user]:[group] [file].

For example, `chown john:devs file.txt` changes the owner to `john` and group to `devs`.

??? question "15. Which command prints all environment variables?" env (or printenv).

It lists the current environment variables and their values.

??? question "16. Which command creates an environment variable accessible to child processes?" export VAR=value.

Without `export`, the variable is only available in the current shell session.

??? question "17. What is the difference between absolute and relative paths?" Absolute path: Starts from the root / (e.g., /home/user/file). Relative path: Starts from the current directory (e.g., ../file or docs/file).

??? question "18. Which command is safer for copying large directory structures?" rsync.

Unlike `cp`, `rsync` supports resuming interrupted transfers, delta updates (only copying changed parts), and explicitly preserving permissions.

??? question "19. Which command lists files in a tree-like format?" tree.

It provides a visual recursive directory listing.

??? question "20. Which command checks the version of text editor installed?" vi --version (or vim --version).

`vi` (or `vim`) is the standard text editor available on almost all Linux systems.

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