fcopy inchan outchan ?-size size? ?-command callback?
The fcopy command transfers data from inchan until end of file or size bytes have been transferred. If no -size argument is given, then the copy goes until end of file. All the data read from inchan is copied to outchan. Without the -command option, fcopy blocks until the copy is complete and returns the number of bytes written to outchan.
The -command argument makes fcopy work in the background. In this case it returns immediately and the callback is invoked later when the copy completes. The callback is called with one additional argument that indicates how many bytes were written to outchan. With a background copy, it is not necessary to put inchan or outchan into non-blocking mode; the fcopy command takes care of that automatically. However, it is necessary to enter the event loop by using the vwait command or by using Tk.
You are not allowed to do other I/O operations with inchan or outchan during a background fcopy. If either inchan or outchan get closed while the copy is in progress, the current copy is stopped. If inchan is closed, then all data already queued for outchan is written out.
Note that inchan can become readable during a background copy. You should turn off any fileevent handlers during a background copy so those handlers do not interfere with the copy. Any I/O attempted by a fileevent handler will get a "channel busy" error.
Fcopy translates end-of-line sequences in inchan and outchan according to the -translation option for these channels. See the manual entry for fconfigure for details on the -translation option. The translations mean that the number of bytes read from inchan can be different than the number of bytes written to outchan. Only the number of bytes written to outchan is reported, either as the return value of a synchronous fcopy or as the argument to the callback for an asynchronous fcopy.
The second example copies in chunks and tests for end of file in the command callbackproc Cleanup {in out bytes} { global total set total $bytes close $in close $out } set in [open $file1] set out [socket $server $port] fcopy $in $out -command [list Cleanup $in $out] vwait total
proc CopyMore {in out chunk bytes} { global total done incr total $bytes if [eof $in] { set done $total close $in close $out } else { fcopy $in $out -command [list CopyMore $in $out $chunk] \ -size $chunk } } set in [open $file1] set out [socket $server $port] set chunk 1024 set total 0 fcopy $in $out -command [list CopyMore $in $out $chunk] -size $chunk vwait done
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