Writes a data to the file.
filewrite <file handle> <data>
Writes <data> to the file specified by <file handle>.
When the <data> type is the character string, the data is written as string.
When the <data> type is the integer, the least significant byte(0-255) regards as the ASCII code and
the ASCII character is written.
filewrite fhandle '---------cut here---------'#13#10
; write a NUL character (0x00). filewrite fhandle 0