LIST FILES IN LINUX: “ls” COMMAND 

As it was said, the command ls allows you to list files and folders of a specific path, is easy to use and is very useful and used in the daily work. The command has several options to improve the listings. In a terminal, we can invoke the help of the command ls in this way.

ls --help 

Above command will display all options available for ls command to list the files and folders. In this way we get the syntax of usage and options as output per terminal.

As all options will not cover in one single screenshot so i have scrolled the above screen and taken another screenshots to cover all options in screenshots that has been displayed below.

As we can see the documentation is extensive, but don’t worry we will examine the most useful and used options. The basic syntax of the command is:

ls [options] [file|dir]

Although it is possible to use ls from the most basic form only by typing:

#List files from your given directory.
ls

With this we only list the files that are in the directory where we are located in the terminal. For example, if we wanted to list everything in the root directory of our GNU/LINUX distribution it would be with the command:

#List everything in the root directory
ls /

It was easy, wasn’t it?

Most Important Options of the Command “ls”

ls as well as all GNU/LINUX commands have options that modify the basic command execution result. Here is a list of the most outstanding ones for this command.

 Examples of Command “ls”

Here i have given different examples of command ls that you can use to fulfill different requirements.

List Hidden Files 

We can use option -a if we want to list the hidden files of a specific folder, it would be enough to write:

ls –a path

In my case it would be something like that:

ls –a /home/angelo/

You can see all hidden files as well in above screenshot. We can identify hidden files by looking at the output as such files or folders start with dot (.).

Display Files with their Index Number

We can list files with their index number by running below command. To show files/folders with their index number we will use the option –i along with command ls. You can see i have used below command and output is showing in below image.

ls -i /home/angelo/
 

List Files with full Details (Permissions, Index no, Owner, Create Date etc.)

We can use ls command to display information such as permissions and owner of the folder or file. We will be using option -I to show complete information about files and folders as shown in below screenshot.

ls -l /home/angelo/

This output shows us more specific information about what we have in the folder: First it shows the permissions on the folder, its index number, the owner of the folder, who created the folder, its size in kb, the date it was modified and the folder name.

List Files or Folders in a Reverse Order

ls command also gives an option to sort files and folders in reverse order. We can use -r option to show files and folders in a reverse order as shown in below screenshot after running below command.

ls –r  /home/angelo/

List Subdirectories Recursively

We can List subdirectories recursively by adding the -R option with ls command.  It will display the contents of the directory subfolders. Run below command to display the result.

ls –R /home/angelo/

 Display list of Directories Only

We can use -d and an asterisk option to list and show only the directories. Have a look at below command that has displayed the list of directories under /home/angelo.

ls –d */home/angelo/

Display Files Sort by their File Size

Run below command to display files sort by file size. It is possible with the option –S.

ls -S /home/angelo/

Sort by Date/Time

We can option -t to display files sort by date/time. Run below command to see the output that is also showing in below screenshot.

ls –t /home/angelo/

Display Files as they were Created

Use option -U to show folders and files in no order at all. It will display just as they are created.

ls –U /home/angelo/

Sort by File Extension

We can use option -X with ls command to sort files by their extension names. You can see this in below screenshot.

ls –X /home/angelo/

Sort by Modified Files

We can use combination of options -ltr to show last modification file or directory date. Simply run below command to display the output.

ls -lrt

ls -lrt [path]

In conclusion we can say that the ls command, even when it is relatively easy to use, is one of the tools most used by system administrators.

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Read More:

• RHEL Interview Questions & Answers
• Linux User Administration – Add, Delete & Modify User Accounts
• Install HTop and Use it to Monitor Linux Processes
• How to Change Host Name of RHEL system?
• How to Reset or Change Linux User Account Passwords?

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Red Hat Linux Interview Questions and Answers

1. What is Red Hat Enterprise Linux?

Answer – It is a GNU/LINUX distribution created and developed by the multinational enterprise oriented company Red Hat, being the basis for deploying cloud applications, servers or data center.

2. Which is the package manager used by RHEL?

Answer – The package manager in RHEL is YUM.

3. How do I install a program in RHEL?

Answer – Installing a package or program in RHEL is simple thanks to YUM. With root permission we type in a terminal.

yum install package_name

4. How can I update the packages in RHEL?

Answer – Run below command to update all packages in your RHEL system.

yum upgrade

5. How can I remove the packages in RHEL?

Answer – Run below command to remove any package from RedHat Linux system.

#Make sure to change the name of package that needs to be removed.
yum remove package_name

6. How can I create a user in RHEL?

Answer – We can create a new user from the terminal with the command:

#Pass the user name in place of user_name 
useradd user_name

7. How can I change the user password?

Answer – The command that allows us to change the password of the active user is passwd. By entering the command in the terminal, you will be prompted for the current password and twice for the new password. Read below article to learn step by step process to change user as well as sudo passwords.

• How to Reset or Change User Password on RHEL?

8. How can I change the system language?

Answer- In RHEL, the system language can be changed using the following command:

localectl set-locale LANG=”xx_XX.utf8”

For example, if the system is in English and we want to change to German

localectl set-locale LANG=de_DE.utf8

Then simply restart the active session (not the system)

9. What is a GNU/LINUX service?

Answer – A service is a program that runs in the background, outside the interactive control of the users of the system.

10. How can I list the services that are running in RHEL?

Answer – This is very useful when managing systems in GNU/LINUX. We can list all the services that are running with the command:

systemctl -t service --state=active

If you want to check specific service running on RHEL then you can pass service name in above command. For example, i want to check SQL Server service running on my RHEL system then i will run below command. This command will show the output for only this service.

systemctl status mssql-server

11. How can I start or stop a service?

Answer – During the administration of a GNU/LINUX based server we will have to initialize and also stop services.

To initialize:

systemctl start name.service 

To Stop:

systemctl stop name.service

To Restart:

systemctl restart name.service

12. How do I know which version of the kernel I am using?

Answer – To know which version of the Linux Kernel we are using, just use the command:

uname –r

13. How can I add and remove kernel modules?

Answer – The kernel modules are small programs or libraries that are added to the kernel so that it can manage hardware devices. To add or remove it we use the command modprobe.

For example, to add a module:

modprobe module_name

And to remove a module

modprobe –r module_name

14. What is the file system RHEL uses?

Answer – The file system used by RHEL is XFS

15. How do I know how much space is available on my hard disk with RHEL?

Answer – This is useful to know when we are reaching the hard disk capacity. With the command:

df –h

16. Can I change hostname in RHEL?

Answer – Yes. There are multiple ways to change hostname of a RHEL system. For example if we want hostname to be example. com, we must write the following command in a terminal:

hostnamectl set-hostname example.com

I have explained it in below article in very details way. Have a look at this article to learn the process to rename or change the hostname of RHEL system.

• How to Change Hostname of RHEL system?

17. How do I know the IP address of the equipment in RHEL?

Answer – With the command:

nmcli dev show

We will not only be able to see the ip address, but also the complete information of all the network interfaces. You can read below article to learn how to check and change the IP address, subnet mask etc of a RHEL system.

• How to Find and Change IP Address, Subnet Mask and Default Gateway of RHEL system?

18. Can I install a Web server in RHEL?

Answer- Of course, we can install the web server we want: Apache, nGix or other.

19. After installing Apache2, where is the default Document Root located?

Answer – By default the apache2 DocumentRoot in RHEL sets it to /var/www/html/

20. How do I know which version of Red Hat Enterprise Linux is running the server?

Answer – Run the command in a terminal to get the RHEL version running on your system.

/etc/redhat-release

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