With Linux, it’s very easy to navigate directories and files using just few commands. In fact, it can be even faster than normal GUI desktop. Usually, terminal operations are lot faster than GUI based operations. This lesson shows how we can read the contents of the file and how to navigate around the directories in Linux.

In this lesson, we will explore some of the command we learned in the previous lesson.

pwd

Home Directory

By default, we are in user’s home directory which looks something like below. Everytime we open Terminal session in UNIX machine, it opens in this home directory. In home directory, the current user will have all permission. We will talk about permissions in one of the later lessons.

/home/username

Root Directory Structure

We can navigate to root directory using cd /. Here, we see all system level directories. Type ls to see directories available here. Below are some of the common directories in root directory of Linux system. Depending on operating system some of these may not be present.

  • /bin (Binaries): This directory contains essential binary executables (commands) required for basic system operations. Common commands like ls, cp, mv, rm are stored here.
  • /boot: The /boot directory contains files related to the boot process of the system. Bootloader configuration files, kernel images, and initial RAM disk files reside here.
  • /dev (Device): This directory holds special device files that represent physical or virtual devices attached to the system. Devices such as hard drives (e.g., /dev/sda), CD-ROMs (e.g., /dev/cdrom), and USB devices can be accessed via these device files.
  • /etc: This directory stores system-wide configuration files used by various applications and services. Network settings, startup scripts, user account details, etc., can be found in this directory.
  • /home: Each user on a Linux system typically has their own home directory located under this root directory. User-specific files such as documents, downloads, configurations, and personal settings can be found here.
  • /lib (Library): Essential shared libraries required by binaries under the /bin and /sbin directories are stored here. These libraries provide functions used by various applications at runtime.
  • /media: This directory is used as a mounting point for removable media devices (e.g., USB drives, CD/DVDs). When a removable media device is connected to the system, it gets automatically mounted under this directory.
  • /opt (Optional Packages): It is commonly used to store additional software packages that are not part of the core Linux distribution.
  • /proc (Process Information): This directory provides a virtual file system that contains information about running processes and system configuration. Information about CPU, memory, hardware, and other kernel-related details can be accessed through files within this directory.
  • /root: The root user’s home directory is located here (/root) which may have important configuration files specific to the root user.
  • /sbin (System Binaries): It contains essential system binaries required for administrative tasks like mount, umount, reboot are stored in this directory accessible only by administrators.
  • /tmp (Temporary): It is used for temporary storage of files and directories. The contents of this directory may not persist across reboots.
  • /usr (Unix System Resources): This holds non-essential utilities, libraries, documentation, and resources for typical users. It further subdivides into subdirectories like /usr/bin (user binaries), /usr/lib (user libraries), and so on.
  • /var (Variable Data): This contains variable data such as logs, spool files, cache data, etc. It contains information that might change frequently during system operation.

To navigate back to previous directory, we can use cd -. This will take us to previous location, in this case the home directory.

Absolute and Relative Path

Now that we are in the home directory the user, we can create new files and directories in two ways. If we write pathnames without prefix of / then that will be relative to our current path. That is also known as relative path in Linux.

mkdir something

Above command will make something directory in the current path,. That is, it will create path /home/username/something. Similarly, if we were inside /home/username/folder and executed this command, it will create new directory relative to that location. Please, note that relative path can be specified without any prefix, but sometimes, you may notice relative path for scripts specified using ./ prefix. In Linux . refers to current directory. So, you can also type commands like ls . or cd ..

On the other hand, if we want to create the same directory using Absolute path, we would have to specify full path like below.

mkdir /home/username/something

This is called absolute path.

Practical Demo

Create Directory and Navigating File System

Ok, let’s create our directory and try to create directories and files inside it.

mkdir bash-session # create directory
cd bash-session # change into new directory
mkdir folder1
mkdir folder{2..3}
ls # list current directory

Here, we have three directories.

folder1 folder2 folder3

To display only folders Let’s remove them and recreated a nested directory structure where we will create our first file.

rmdir folder{1..3} # remove multiple empty directories
ls # No directories or files

mkdir dir1/inside_dir1 # produces error because dir1 does not exist
mkdir: cannot create directory ‘dir1/inside_dir1’: No such file or directory

Above command fails because when shell tries to create child directory inside_dir1, it did not find the parent directory. By default, mkdir assumes that the parent directory exists. If we want to create parent directory if it does not exist, then we have to use -p option with this command.

mkdir -p dir1/inside_dir1 # works fine because -p can create path if not exists
cd dir1/inside_dir1/
touch hello.txt # create 'hello.txt' file
echo "Hello" # prints Hello on terminal

To navigate back to bash-session, we can type cd .. which brings us to dir1/ and then again cd .. which brings us to bash-session directory. Alternatively, we can type cd ../../ which will take us two steps up.

To recursively list files and directories in current directory, we can use -R option with ls command.

ls -R
  • We can find all files or directories that start with keyword my using ls my*.
  • To find items ending with numbers 2 and 3, we can use something like ls dir[23]
mkdir dir{2..5}
ls dir[23]

Move, Copy, Rename Files

touch dir1/test1.txt
touch dir2/test2.txt

Now, to copy file dir1/test1.txt to dir3/test3.txt we can use below syntax.

cp dir1/test1.txt dir3/test3.txt
ls dir3

For copying and moving files, if the file with given name already existed, it will overwrite it. To avoid such situation, we can use cp -i or mv -i. This will always prompt the user to make sure the user wants to overwrite the file.

cp -i dir1/test1.txt dir3/test3.txt
cp: overwrite 'dir3/test3.txt'? n

By default, when we perform cp dir1/* dir5/, it will copy only the files, but if we want to move all contents of dir1 including directories, we can use cp -r which recursively copies everything from dir1.

cp -r dir1/* dir5

To move file from dir3/test3.txt into dir4/, we can use mv command. Note that moving a file removes the file from the source and moves it to destination.

mv dir3/test3.txt dir4/

To rename a file, we use the same mv command. In this case, we just name file differently which is same as moving file to differently named file.

mv dir1/test1.txt dir1/sample.txt
ls dir1
inside_dir1  sample.txt

Before, we go further, we have to learn few more Linux commands.

echo: Printing

The echo command is used to display text on the terminal or redirect it into a file.

  • Syntax: echo [OPTIONS] [STRING]
  • Usage:
    • Writing to the console: echo "Hello World"
    • Writing to a file: echo "Linux is awesome" > linux.txt

cat: Read files and Display content

The cat command is used for reading files sequentially and displaying their contents on the terminal.

  • Syntax: cat [OPTIONS] [FILE(S)]
  • Usage:
    • Read file content and display on terminal: cat file.txt
    • Combine two files into single file: cat file1.txt file2.txt > combined.txt

head: Print first part of file

The head command displays the beginning lines of a file. By default, it shows the first 10 lines but can be customized using options.

  • Syntax: head [OPTIONS] [FILE(S)]
  • Usage:
    • Display first 10 lines: head file.txt
    • Display first 5 lines: head -n 5 file.txt

tail: Print last part of file

Description: The tail command displays the ending lines of a file. By default, it shows the last 10 lines but can be customized using options.

  • Syntax: tail [OPTIONS] [FILE(S)]
  • Usage:
    • Display last 10 lines of a file: tail file.txt
    • Display last 3 lines of a file: tail -n 3 access.log

Let’s say we have a file hello.txt with below content in it.

line 1
line 2
line 3
line 4
line 5
line 6
line 7

Now, to read the contents of this file, we can use below commands. Please, note that in this small file, we have only 7 lines, so head command by default will show all 7 lines, but if the file was larger than 10 lines, it would display only first 10 lines.

cat hello.txt # displays full content of the file
head hello.txt # shows 10 lines, in this case, full file
head -n 5 hello.txt # shows first 5 lines
tail hello.txt # shows last 10 lines
tail -n 3 hello.txt # shows last 3 lines.

Linked Files

If you need to maintain two or multiple copies of the same file on the system, instead of having separate copies, we can create virtual copies. These are called links. There are two types of links in Linux:

This is simply a physical file that points to another file in the virtual directory structure.

touch hello.txt
ln -s hello.txt hello_symbol.txt
ls -l

Below output shows that symbolik link hello_symbol.txt has lot smaller size. Modifying one file will modify the original file.

-rw-r--r-- 1 user group 45 Sep 15 13:02 hello.txt
lrwxrwxrwx 1 user group  9 Sep 15 13:01 hello_symbol.txt -> hello.txt

This is largely used in Linux configuration files which reside in one location but can be added to another location using symbolic links.

This creates a separate virtual file that contains the same information as the original file. However, these are two separates files. When we reference the hard link file, it’s same as reading the original file. To create hard link, the original file must exist.

ln hello.txt hello_hard.txt
ls -l

Below output shows that hard links have exactly the same size as the original file.

-rw-r--r-- 2 piyushpatel2005 piyushpatel2005 45 Sep 15 13:02 hello.txt
-rw-r--r-- 2 piyushpatel2005 piyushpatel2005 45 Sep 15 13:02 hello_hard.txt
lrwxrwxrwx 1 piyushpatel2005 piyushpatel2005  9 Sep 15 13:01 hello_symbol.txt -> hello.txt

To unlink these links, we can use below command:

unlink hello_hard.txt
unlink hello_symbol.txt