ls (List Directories)

Now that we know how to move around the filesystem, how do we figure out what is available to us? The ls command lists files and directories so you can inspect your current location or another path.

Basic Usage of the ls Command

By default, the ls command will list the directories and files in your current directory. However, you can also specify a path to list the contents of a different directory.

$ ls
$ ls /home/pete

You can list a specific file too:

$ ls /etc/hosts
/etc/hosts

Viewing Hidden Files

Not all files in a directory are visible by default. In Linux, filenames that start with a dot (.) are hidden. You can view them with the -a option, which stands for all.

$ ls -a
.  ..  .bashrc  Documents  Pictures

Dotfiles are hidden by default and often store configuration, such as .bashrc.

Getting Detailed Information

Another essential ls option is -l for long format. It shows file permissions, number of links, owner, group, size, modification time, and name.

$ ls -l

Here is an example of the output:

pete@icebox:~$ ls -l
total 80
drwxr-x--- 7 pete penguingroup   4096 Nov 20 16:37 Desktop
drwxr-x--- 2 pete penguingroup   4096 Oct 19 10:46  Documents
drwxr-x--- 4 pete penguingroup   4096 Nov 20 09:30 Downloads
drwxr-x--- 2 pete penguingroup   4096 Oct  7 13:13   Music
drwxr-x--- 2 pete penguingroup   4096 Sep 21 14:02 Pictures
drwxr-x--- 2 pete penguingroup   4096 Jul 27 12:41   Public
drwxr-x--- 2 pete penguingroup   4096 Jul 27 12:41   Templates
drwxr-x--- 2 pete penguingroup   4096 Jul 27 12:41   Videos

For easier file sizes, add -h for human-readable output:

$ ls -lh

Sorting in Reverse Order

Sometimes you may want to change the sort order. The -r option lists files and directories in reverse order.

$ ls -r

You can sort by modification time with -t, then reverse it with -r:

$ ls -lt
$ ls -ltr

Combining Command Flags

Commands have flags, also called options, to add more functionality. As we saw with -a and -l, you can combine them into a single command like ls -la. The order of the flags often does not matter, so ls -al works the same way.

$ ls -la

Useful combinations include:

$ ls -lh
$ ls -la
$ ls -ltr

Common ls Options

• -a: Show all files, including hidden files.
• -l: Use long format.
• -h: Show human-readable sizes with -l.
• -r: Reverse the sort order.
• -t: Sort by modification time.
• -S: Sort by file size.
• -d: List the directory itself instead of its contents.

Some systems display ls output in different colors for different file types. This behavior commonly comes from an alias or environment setting, so colors may vary between systems.

To reinforce your understanding of the ls command, try this hands-on lab:

• Linux ls Command: Content Listing - Practice using the ls command to efficiently list and analyze file and directory contents. You'll learn various options for detailed listings, hidden file display, human-readable sizes, and sorting techniques to enhance your command-line skills.

This lab will help you apply the concepts in a real scenario and build confidence with directory listing in Linux.

Summary

You can now use ls to inspect directory contents and control how entries are displayed.

1. List the current directory or another path.
2. Include hidden files in a listing.
3. Show detailed information with readable sizes.
4. Sort entries by modification time in reverse order.
5. List a directory entry without listing its contents.