Making scripts executable (chmod +x) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the command chmod +x script.sh do?

It adds execute permission to the file script.sh, allowing it to be run as a program.

beginner

Why do you need to make a script executable before running it?

Because the operating system requires execute permission to run a file as a program. Without it, you can only read or edit the script, not run it directly.

intermediate

What is the difference between chmod +x script.sh and chmod 755 script.sh?

chmod +x adds execute permission to the existing permissions. chmod 755 sets read, write, and execute for owner and read and execute for group and others explicitly.

beginner

How can you check if a script is executable?

Use ls -l script.sh. If you see an x in the permission string (e.g., -rwxr-xr-x), it means the script is executable.

beginner

What happens if you try to run a script without execute permission?

You will get a 'Permission denied' error if you try to run it directly. However, you can still run it by calling the interpreter explicitly, like bash script.sh.

What does chmod +x myscript.sh do?

A Copies the script

B Makes the script executable

C Changes the script owner

D Deletes the script

The command adds execute permission to the script, allowing it to be run.

Which command shows if a file is executable?

A ls -l filename

B cat filename

C rm filename

D touch filename

The ls -l command lists file permissions, showing if execute permission is set.

If a script is not executable, how can you still run it?

A By running <code>bash script.sh</code>

B By double-clicking it

C By renaming it

D By deleting it

Calling the interpreter explicitly runs the script without needing execute permission.

What permission does chmod +x add?

A Read permission

B Write permission

C Delete permission

D Execute permission

The +x flag adds execute permission to the file.

What error appears if you run a script without execute permission?

A Syntax error

B File not found

C Permission denied

D Command not found

Trying to run a non-executable script directly results in a 'Permission denied' error.

Explain why and how you make a script executable in bash.

Think about what the system needs to allow running a file as a program.

Describe how to check if a script is executable and what the permission string looks like.

Look at the file permissions shown by ls.