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.