What is the primary purpose of the 'chmod' command?

The primary purpose of the 'chmod' command is to change the permissions of a file. In Unix-like operating systems, file permissions dictate who can read, write, or execute a file. The 'chmod' command allows users to modify these permissions for the file owner, the group, and others.

When using 'chmod', you can set permissions in numeric format (using octal values) or symbolic format (using letters to represent users and actions). For example, using 'chmod 755 filename' would grant the owner full permissions (read, write, execute) and allow group and others to read and execute the file. This capability is crucial for managing access control to files and ensuring that only authorized users can perform certain actions, thus maintaining security within the system.

Other options do not reflect the purpose of 'chmod': changing ownership is handled by the 'chown' command, moving a file falls under the 'mv' command, and displaying a file's content is managed by commands like 'cat' or 'less'. Thus, understanding the specific functionalities of these commands helps illuminate why 'chmod' is specifically focused on permission changes.