What does '755' represent in the command 'chmod -R 755 ~/test-dir'?

In the command chmod -R 755 ~/test-dir, the 755 represents the permissions that are being set for the files and directories within ~/test-dir.

Here's a breakdown of what 755 means:

• The first digit 7 sets the permissions for the owner of the file:

  • 4 (read) + 2 (write) + 1 (execute) = 7 (full permissions).

• The second digit 5 sets the permissions for the group:

  • 4 (read) + 1 (execute) = 5 (read and execute permissions, but no write).

• The third digit 5 sets the permissions for others:

  • 4 (read) + 1 (execute) = 5 (read and execute permissions, but no write).

So, 755 means:

• The owner can read, write, and execute.
• The group can read and execute.
• Others can read and execute.

The -R option means that the command is applied recursively to all files and subdirectories within ~/test-dir.