What command is used to change file permissions from the command line?

The command used to change file permissions from the command line is chmod. This command allows users to modify the read, write, and execute permissions for files and directories in a Linux environment.

When using chmod, you can specify permissions in symbolic mode (using letters such as r for read, w for write, and x for execute) or numeric mode (using numeric values like 4 for read, 2 for write, and 1 for execute). This flexibility makes it a powerful tool for managing access permissions on files and ensuring that users can interact with files in appropriate ways.

Other commands listed have different functionalities. For instance, chgrp is used to change the group ownership of a file or directory, while chage is used for managing password expiration or aging for user accounts. The term "modify" does not correspond to any specific command in Linux for changing file permissions. Therefore, the function of chmod specifically addresses the need to alter file permissions, confirming it as the correct choice.