chmod (change permissions) in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of ls -l after running chmod 754 file.txt?

You have a file named file.txt. You run the command chmod 754 file.txt. What will be the permission string shown by ls -l file.txt?

Linux CLI

chmod 754 file.txt
ls -l file.txt

A -rwxr-xr-- 1 user group 0 date file.txt

B -rwxr-xr-x 1 user group 0 date file.txt

C -rwxr--r-x 1 user group 0 date file.txt

D -rwxr--r-- 1 user group 0 date file.txt

💡 Hint

Remember the digits in chmod represent owner, group, and others permissions in octal.

The number 7 means read, write, execute (rwx) for owner. 5 means read and execute (r-x) for group. 4 means read only (r--) for others. So the permission string is '-rwxr-xr--'.

💻 Command Output

intermediate

What error occurs when running chmod 999 file.txt?

You try to set permissions with chmod 999 file.txt. What happens?

Linux CLI

chmod 999 file.txt

A chmod: cannot access 'file.txt': No such file or directory

B Permission changed successfully

C chmod: invalid mode: ‘999’

D chmod: invalid argument ‘999’

💡 Hint

Check if the mode digits are valid octal numbers.

Digits in chmod must be octal (0-7). '9' is invalid, so chmod reports 'invalid mode'.

📝 Syntax

advanced

Which command correctly adds execute permission for the group on script.sh?

You want to add execute permission for the group only, without changing other permissions. Which command is correct?

A chmod g+x+ script.sh

B chmod +x g script.sh

C chmod x+g script.sh

D chmod g+x script.sh

💡 Hint

The syntax is chmod [who]+[permission] file.

The correct syntax to add execute permission for group is 'chmod g+x file'. Other options are invalid syntax.

🚀 Application

advanced

How to set permissions so owner has full access, group has read-only, and others have no access on data.txt?

You want data.txt to have these permissions: owner can read, write, execute; group can only read; others have no permissions. Which command achieves this?

A chmod 740 data.txt

B chmod 700 data.txt

C chmod 754 data.txt

D chmod 744 data.txt

💡 Hint

Convert permissions to octal: rwx=7, r--=4, ---=0.

Owner rwx=7, group r--=4, others ---=0 gives 740.

🧠 Conceptual

expert

What is the effect of chmod u=rwx,g=rx,o= file.txt?

You run chmod u=rwx,g=rx,o= file.txt. What permissions does file.txt have?

A Owner has read and write; group has read only; others have execute only

B Owner has read, write, execute; group has read and execute; others have no permissions

C Owner has full permissions; group and others have full permissions

D Owner has no permissions; group has read and execute; others have read only

💡 Hint

Look at each user class and the permissions assigned explicitly.

The command sets owner (u) to rwx, group (g) to rx, and others (o) to no permissions.