Read Long-Listing Permissions

The teacher sees a report in a directory but wants to know who can read or change it. ls -l includes a compact mode field near the start of the listing. At first it looks like a string of unrelated letters; once you split it into parts, it becomes much easier to read.

The first character describes the entry type. The next nine positions form three triplets for owner, group and others. We will read the ordinary bits first, then recognize that ACLs and other system rules can add information beyond this short display.

Prepare the example

Use a new practice directory. The first line creates a small report, and chmod gives it a known ordinary mode for the reading exercise. That preparation avoids relying on whatever default mode your environment happened to choose.

Bash · Linux terminal

printf 'Diya: 72\n' > marks.txt
chmod 640 marks.txt
ls -l marks.txt

Expected behavior; machine-dependent details

The mode begins -rw-r-----; owner, group, size and dates vary.

After chmod 640 marks.txt, ls -l marks.txt should show the ordinary mode as -rw-r-----. The leading - indicates a regular file. Owner rw- allows read and write, group r-- allows read, and others --- grants no ordinary permission bits. A dash in a triplet means that bit is absent.

Read the owning user and group fields alongside the triplets, because they identify the classes. Names, sizes and dates vary across systems. If an extended ACL exists, the group-class display can reflect its mask; use getfacl for the additional entries. The listing is a useful starting point, not a complete guarantee about every possible access constraint.

ls -l shows more than filenames. Its long format includes the file type, permission bits, link count, owner, group, size and modification time.

Step 1: Open your terminal

You can use any terminal. If you're using a Mac or Linux machine, just open the Terminal app. On Windows, use WSL or any Linux shell.

Step 2: Use the ls -l command

Let’s look at the contents of your current directory in long listing format:

ls -l

You’ll see an output that looks like this:

-rw-r--r--  1 user  user   1024 Jul  2 10:00  notes.txt
drwxr-xr-x  2 user  user   4096 Jul  1 09:30  documents
-rwxr-xr--  1 user  user   2048 Jul  1 14:15  script.sh

Step 3: Understand the output

Let’s break down the line for script.sh:

-rwxr-xr--  1 user  user   2048 Jul  1 14:15  script.sh

• -: This indicates it's a file (d for directory)
• rwx: The owner (user) has read (r), write (w), and execute (x) permissions
• r-x: The group has read and execute permissions
• r--: Others (everyone else) only have read permission

The permissions are grouped like this:

• First character: File type (- for file, d for directory)
• Next 3 characters: User permissions
• Next 3 characters: Group permissions
• Last 3 characters: Others (world) permissions

Practice reading permissions on a test file

Create a file and check its permissions:

touch test.txt
ls -l test.txt

-rw-r--r--  1 user  user  0 Jul 2 11:00 test.txt

This tells us that the user can read and write the file, while the group and others can only read it.

Step 5: View permissions of all files and folders

You can also view permissions recursively inside subdirectories:

ls -lR

This is useful if you want to audit the entire structure.

Read an ls -l permission string from left to right

File permissions in Linux control who can do what with a file or folder. Use ls -l to view them. Each permission set is shown as a series of characters, grouped by owner, group, and others.

Understanding permissions is the first step to becoming confident in managing your Linux system securely and effectively.

Your task: Interpret the group triplet r--.

Use a new practice directory. The first line creates a small report, and chmod gives it a known ordinary mode for the reading exercise. That preparation avoids relying on whatever default mode your environment happened to choose.

Bash · complete example for this question

printf 'Diya: 72\n' > marks.txt
chmod 640 marks.txt
ls -l marks.txt

Expected behavior; machine-dependent details

The mode begins -rw-r-----; owner, group, size and dates vary.

Worked answer

Group read is allowed by these bits.

The group triplet r-- includes read, not write or execute. It does not say that every user can read. Identify which class applies to the reader and keep directory traversal or other access controls in mind when predicting a real operation.

Split the mode field instead of memorizing its whole string: type, owner, group, others. Read the names that define those classes and recognize missing bits. When a short listing does not explain access, inspect ACLs and the relevant directory path rather than assuming the display is wrong.