What does chmod +x filename command do?

You may see a Permission denied error when you try to execute a Python, Shell, or Bash scripts on Linux distributions, Unix, or macOS Terminals.

Example: zsh shell on macOS

% ./script.sh

zsh: permission denied: ./script.sh




Example: Sh Shell

# ./script.sh

bash: ./script.sh: Permission denied




Example: Bash Shell

$ ./script.sh

sh: ./script.sh: Permission denied

Now let's take a look at file permissions using ls command on the script.sh file.

% ls -ls script.sh 

0 -rw-r--r--  1 c2ctechtv  staff  0 Jul 16 02:49 script.sh

Let's try to understand what permissions we have on the file using a table.

Permission	User	Group	Others
Read (r)	✓	✓	✓
Write (w)	✓
Execute (x)

As you can see not of the users have the execute permission enabled, hence the erorr.

Let's make use of chmod +x on the file.

% chmod +x script.sh

% ls -l chmod+x script.sh

-rwxr-xr-x  1 c2ctechtv  staff  0 Jul 16 02:49 script.sh

Permission	User	Group	Others
Read (r)	✓	✓	✓
Write (w)	✓
Execute (x)	✓	✓	✓