function onCommand( file ) {
		var err;
		if ( !isString( file ) ) {
			err = new TypeError( format( 'invalid argument. Must provide a string. Value: `%s`.', file ) );
			debug( 'Error: %s', err.message );
			pres._repl._ostream.write( 'Error: '+err.message+'\n' );
			return;
		}
		pres._repl.once( 'drain', onDrain );

		/**
		* Callback invoked upon a `drain` event.
		*
		* @private
		*/
		function onDrain() {
			var pos;
			try {
				pres.load( file ).show();
			} catch ( error ) {
				debug( 'Error: %s', error.message );

				// Infer the current cursor column position based on the length of the command prompt string:
				pos = pres._repl._prompt().length; // FIXME: how to address multi-column characters?

				// FIXME: handle non-TTY output streams!

				/*
				* Print the error message on the previous line and generate the expected display prompt and cursor position.
				*
				* [ANSI escape sequences][1]:
				*
				* -   `\u001b`: ESC, the escape character
				* -   `[1A`: move cursor up one line
				* -   `[nD`: move cursor back (to the left) `n` columns (cells)
				* -   `[0J`: clear the screen beginning from the current cursor position to the end of the screen
				*
				* [1]: https://en.wikipedia.org/wiki/ANSI_escape_code
				*/
				pres._repl._ostream.write( '\u001b[1A\u001b['+pos+'DError: '+error.message+'\u001b[0J\n' );

				// Show a new display prompt:
				pres._repl._displayPrompt();
			}
		}
	}
Loads a presentation from a file.

## Notes

-   Relative file paths are resolved relative to the current working directory.

@private
@param {string} file - file path