What command is used to change permissions of a file in Linux?

The command used to change permissions of a file in Linux is "chmod." This command stands for "change mode," and it allows users to specify who can read, write, or execute a file.

Permissions in Linux are categorized into three types: read (r), write (w), and execute (x), and they can be applied to three categories of users: the owner of the file, the group associated with the file, and others. Using "chmod," you can modify these permissions by either using symbolic notation (e.g., "chmod u+x filename" to add execute permission for the user) or numeric notation (e.g., "chmod 755 filename" to set specific permissions for the owner, group, and others).

The other options provided are not valid commands in Linux for changing file permissions, which highlights "chmod" as the correct and widely recognized command for this function.