To hide the file on a Linux system, you have to start the filename with a specific character. What is the character?

The tilde (~) character typically represents the current user's home directory in shell environments, not a prefix for hiding files.

An underscore (_) is a valid character for filenames but does not confer any special 'hidden' status on a file in Linux.

On Linux and other Unix-like systems, files and directories whose names start with a period ('.') are treated as hidden by convention and are not displayed by default by common commands like `ls` unless the `-a` (all) option is specified. This is a fundamental aspect of the Linux file system.

The exclamation mark (!) is a special character often used in shell scripting for history expansion or specific operations, but it does not indicate a hidden file.