Add a newline and append `contents` to the file.

Removes any lines matching `line` in the file.

Returns true if the directory exists.

Returns true if the file contains the given line exactly.

Returns true if the file is empty.

Returns true if the file exists.

Replaces the contents of file `filename` with `contents`.

Add `contents` and a newline to the start of the file.

Return contents of a file as a string.