fcopy man page on OpenDarwin

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fcopy(n)		     Tcl Built-In Commands		      fcopy(n)


       fcopy - Copy data from one channel to another.

       fcopy inchan outchan ?-size size? ?-command callback?

       The  fcopy  command copies data from one I/O channel, inchan to another
       I/O channel, outchan.  The fcopy command leverages the buffering in the
       Tcl  I/O	 system	 to avoid extra copies and to avoid buffering too much
       data in main memory when copying large files to slow destinations  like
       network sockets.

       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 or two additional arguments
       that indicates how many bytes were written to  outchan.	 If  an	 error
       occurred	 during	 the background copy, the second argument is the error
       string associated with the error.  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 and the com‐
       mand callback is not made.  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  transla‐
       tions  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 syn‐
       chronous fcopy or as the argument to the callback for  an  asynchronous

       Fcopy  obeys the encodings configured for the channels. This means that
       the incoming characters are converted internally first UTF-8  and  then
       into  the encoding of the channel fcopy writes to. See the manual entry
       for fconfigure for details on the -encoding option.  No	conversion  is
       done  if both channels are set to encoding "binary". If only the output
       channel is set to encoding "binary" the system will write the  internal
       UTF-8  representation  of  the  incoming	 characters. If only the input
       channel is set to encoding "binary" the system  will  assume  that  the
       incoming bytes are valid UTF-8 characters and convert them according to
       the output encoding. The behaviour of the system for  bytes  which  are
       not valid UTF-8 characters is undefined in this case.

       This  first  example  shows  how the callback gets passed the number of
       bytes transferred.  It also uses vwait to put the application into  the
       event  loop.   Of course, this simplified example could be done without
       the command callback.  proc Cleanup {in out bytes {error {}}} {
	   global total
	   set total $bytes
	   close $in
	   close $out
	   if {[string length $error] != 0} {	   # error occurred during the
	   }  }	 set in [open $file1] set out [socket $server $port] fcopy $in
       $out -command [list Cleanup $in $out] vwait total

       The second example copies in chunks and tests for end of	 file  in  the
       command callback proc CopyMore {in out chunk bytes {error {}}} {
	   global total done
	   incr total $bytes
	   if  {([string  length  $error]  !=  0) || [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

       eof(n), fblocked(n), fconfigure(n)

       blocking,  channel, end of line, end of file, nonblocking, read, trans‐

Tcl				      8.0			      fcopy(n)

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