Fundamental Commands of Linux and Unix (with Examples and Syntax)

Updated: 22 October 2026 · Applies to: Linux and Unix, bash

These are the fundamental file and directory management commands every Linux or Unix user needs.

1. List files: ls

ls

Lists files and directories in your current directory. Add -R to list recursively through subdirectories, or -al for a detailed, columnar listing:

ls -R
ls -al

In ls -al output, the columns are:

1. File type and access permissions
2. Number of hard links to the file
3. Owner
4. Owner's group
5. File size in bytes
6. Date and time of last modification
7. File or directory name

2. List hidden files

ls -a

On Linux and Unix, a hidden file or directory is simply one whose name starts with a dot (.).

3. Create, view and combine files: cat

Create a new file and type content into it directly, then press Ctrl+D to stop and save:

cat > filename

View a file's contents:

cat filename

Combine two files into a new one:

cat file1 file2 > newfilename

The shell does not print a confirmation after this; if nothing went wrong, nothing is shown. Check the result by viewing the new file:

cat newfilename

cat only works reliably this way on plain text files.

4. Delete a file: rm

rm filename

rm deletes without asking for confirmation by default.

5. Move and rename a file: mv

mv filename new_file_location

The same command renames a file when the destination is just a new name in the same directory:

mv filename newfilename

If you get a permission error moving or renaming a file you do not own, run it with sudo:

sudo mv filename newfilename

sudo runs a single command with root privileges after you authenticate with your own password, not the root password.

6. Directory basics

Create a directory in your current location:

mkdir directoryname

Create a directory at a specific path, and more than one at a time:

mkdir /path/to/directoryname
mkdir dir1 dir2 dir3

7. Remove a directory: rmdir

rmdir directoryname

rmdir only removes an empty directory; delete its files and subdirectories first, or use rm -r directoryname to remove a directory and everything in it at once.

8. Rename a directory

mv renames directories the same way it renames files:

mv directoryname newdirectoryname

Other useful commands

• man COMMAND: shows the manual page for a command, similar to a built-in help file.
• history: lists the commands you have run in the current terminal session.
• clear: clears the terminal screen.
• Copy and paste in most terminal emulators: Ctrl+C to copy (where that does not send an interrupt), Ctrl+Shift+V or Shift+Insert to paste, or the terminal's own Edit menu.

Formatting a file for printing: pr

Useful options:

• -x: split the output into x columns.
• -h "header": use "header" as the report header.
• -t: suppress the header and top/bottom margins.
• -d: double-space the output.
• -n: number every line.
• -l page_length: set lines per page (default 56).
• -o margin: set the page margin.

pr -x filename
pr -h "Header" filename
pr -n filename

Printing a file

lp filename

or:

lpr filename

Installing software

Linux distributes software as packages; dependencies are usually separate packages that need installing too. On a Debian or Ubuntu system:

sudo apt-get update
sudo apt-get install packagename

Sending mail from the terminal

Install mailutils first:

sudo apt-get install mailutils

Then send a message:

mail -s 'subject' -c 'cc-address' -b 'bcc-address' 'to-address'

Type the message body, then press Ctrl+D to finish composing and send it.