Which command is used to change the permissions set on a file?

The command used to change the permissions set on a file is indeed "chmod." This command allows users to alter the access levels of files and directories for different user categories, including the owner, group members, and others. With "chmod," you can define whether a user has read, write, or execute permissions for a specific file.

For instance, you can use numeric values to represent permission settings or symbolic notation to make changes more understandable. This flexibility makes "chmod" an essential command for managing file permissions in a Linux environment.

Other commands listed serve different functions: "chown" is used to change the owner of a file, "chgrp" changes the group ownership, and "ls -l" is used to list files in a directory along with their permissions but does not modify them. Thus, these commands do not directly relate to changing permissions like "chmod" does.