copyfile ?-bytes num|-maxbytes num? ?-translate? fromFileId toFileId Copies the rest of the file specified by from- FileId, starting from its current position, to the file specified by toFileId, starting from its cur- rent position. By default, newline translation is disabled for the duration of the copy. If -bytes is specified, then num bytes are copied. If less than num bytes are available, an error is returned. If -maxbytes is specified, then num bytes are copied but no error is returned if less are available. If -translate is specified, then newline transla- tion will not be disabled for the copy. The command returns the number of bytes that were copied. The -bytes option is particularly useful for mixing binary data in with ASCII commands or data in a data stream. This command is provided by Extended Tcl.