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OpenDarwin 7.2.1 - man page for fconfigure (opendarwin section n)

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


       fconfigure - Set and get options on a channel

       fconfigure channelId
       fconfigure channelId name
       fconfigure channelId name value ?name value ...?

       The fconfigure command sets and retrieves options for channels.

       ChannelId  identifies the channel for which to set or query an option and must refer to an
       open channel such as a Tcl standard channel (stdin, stdout, or stderr), the  return  value
       from an invocation of open or socket, or the result of a channel creation command provided
       by a Tcl extension.

       If no name or value arguments are supplied, the command returns a list  containing  alter-
       nating option names and values for the channel.	If name is supplied but no value then the
       command returns the current value of the given option.  If one or more pairs of	name  and
       value are supplied, the command sets each of the named options to the corresponding value;
       in this case the return value is an empty string.

       The options described below are supported for all channels. In addition, each channel type
       may  add  options that only it supports. See the manual entry for the command that creates
       each type of channels for the options that that specific type  of  channel  supports.  For
       example, see the manual entry for the socket command for its additional options.

       -blocking boolean
	      The -blocking option determines whether I/O operations on the channel can cause the
	      process to block indefinitely.  The value of the option must be  a  proper  boolean
	      value.   Channels  are normally in blocking mode;  if a channel is placed into non-
	      blocking mode it will affect the operation of the  gets,	read,  puts,  flush,  and
	      close  commands;	see  the  documentation for those commands for details.  For non-
	      blocking mode to work correctly, the application must be using the Tcl  event  loop
	      (e.g. by calling Tcl_DoOneEvent or invoking the vwait command).

       -buffering newValue
	      If  newValue is full then the I/O system will buffer output until its internal buf-
	      fer is full or until the flush command is invoked. If newValue is  line,	then  the
	      I/O system will automatically flush output for the channel whenever a newline char-
	      acter is output. If newValue is none, the I/O system will flush automatically after
	      every output operation.  The default is for -buffering to be set to full except for
	      channels that connect to terminal-like devices; for these channels the initial set-
	      ting is line.  Additionally, stdin and stdout are initially set to line, and stderr
	      is set to none.

       -buffersize newSize
	      Newvalue must be an integer; its value is used to  set  the  size  of  buffers,  in
	      bytes,  subsequently  allocated for this channel to store input or output. Newvalue
	      must be between ten and one million, allowing buffers of ten to one  million  bytes
	      in size.

       -encoding name
	      This option is used to specify the encoding of the channel, so that the data can be
	      converted to and from Unicode for use in Tcl.  For instance, in order  for  Tcl  to
	      read  characters	from a Japanese file in shiftjis and properly process and display
	      the contents, the encoding would be set to shiftjis.  Thereafter, when reading from
	      the  channel,  the bytes in the Japanese file would be converted to Unicode as they
	      are read.  Writing is also supported - as Tcl strings are written  to  the  channel
	      they will automatically be converted to the specified encoding on output.

	      If  a file contains pure binary data (for instance, a JPEG image), the encoding for
	      the channel should be configured to be binary.  Tcl will then assign no interpreta-
	      tion  to	the  data in the file and simply read or write raw bytes.  The Tcl binary
	      command can be used to manipulate this byte-oriented data.

	      The default encoding for newly opened channels is the same  platform-  and  locale-
	      dependent system encoding used for interfacing with the operating system.

       -eofchar char

       -eofchar {inChar outChar}
	      This  option  supports DOS file systems that use Control-z (\x1a) as an end of file
	      marker.  If char is not an empty string, then this  character  signals  end-of-file
	      when it is encountered during input.  For output, the end-of-file character is out-
	      put when the channel is closed.  If char is the empty string, then there is no spe-
	      cial  end  of  file  character marker.  For read-write channels, a two-element list
	      specifies the end of file marker for input and output, respectively.  As	a  conve-
	      nience,  when  setting  the  end-of-file character for a read-write channel you can
	      specify a single value that will apply to both reading and writing.  When  querying
	      the  end-of-file	character of a read-write channel, a two-element list will always
	      be returned.  The default value for -eofchar is  the  empty  string  in  all  cases
	      except  for files under Windows.	In that case the -eofchar is Control-z (\x1a) for
	      reading and the empty string for writing.

       -translation mode

       -translation {inMode outMode}
	      In Tcl scripts the end of a line is always represented using a single newline char-
	      acter  (\n).   However, in actual files and devices the end of a line may be repre-
	      sented differently on different platforms, or even for  different  devices  on  the
	      same  platform.	For  example, under UNIX newlines are used in files, whereas car-
	      riage-return-linefeed sequences are normally used in network connections.  On input
	      (i.e., with gets and read) the Tcl I/O system automatically translates the external
	      end-of-line representation into newline characters.  Upon output (i.e., with puts),
	      the I/O system translates newlines to the external end-of-line representation.  The
	      default translation mode, auto, handles all the common cases automatically, but the
	      -translation option provides explicit control over the end of line translations.

	      The  value  associated  with -translation is a single item for read-only and write-
	      only channels.  The value is a two-element list for read-write channels;	the  read
	      translation  mode  is the first element of the list, and the write translation mode
	      is the second element.  As a convenience, when setting the translation mode  for	a
	      read-write  channel  you can specify a single value that will apply to both reading
	      and writing.  When querying the translation mode of a read-write	channel,  a  two-
	      element  list  will  always  be  returned.  The following values are currently sup-

	      auto   As the input translation mode, auto treats any  of  newline  (lf),  carriage
		     return  (cr),  or carriage return followed by a newline (crlf) as the end of
		     line representation.  The end of line representation can  even  change  from
		     line-to-line,  and  all  cases  are  translated to a newline.  As the output
		     translation mode, auto chooses a platform specific representation; for sock-
		     ets  on all platforms Tcl chooses crlf, for all Unix flavors, it chooses lf,
		     for the Macintosh platform it chooses cr and for the various flavors of Win-
		     dows it chooses crlf.  The default setting for -translation is auto for both
		     input and output.

	      binary No end-of-line translations are performed.  This is nearly identical  to  lf
		     mode,  except that in addition binary mode also sets the end-of-file charac-
		     ter to the empty string (which disables it) and sets the encoding to  binary
		     (which  disables  encoding  filtering).  See the description of -eofchar and
		     -encoding for more information.

	      cr     The end of a line in the underlying file or device is represented by a  sin-
		     gle  carriage return character.  As the input translation mode, cr mode con-
		     verts carriage returns to newline characters.   As  the  output  translation
		     mode,  cr mode translates newline characters to carriage returns.	This mode
		     is typically used on Macintosh platforms.

	      crlf   The end of a line in the underlying file or device is represented by a  car-
		     riage  return  character  followed  by  a	linefeed character.  As the input
		     translation mode, crlf mode converts carriage-return-linefeed  sequences  to
		     newline  characters.   As	the output translation mode, crlf mode translates
		     newline characters to carriage-return-linefeed sequences.	This mode is typ-
		     ically used on Windows platforms and for network connections.

	      lf     The  end of a line in the underlying file or device is represented by a sin-
		     gle newline (linefeed) character.	In this mode no translations occur during
		     either input or output.  This mode is typically used on UNIX platforms.

       The  Tcl standard channels (stdin, stdout, and stderr) can be configured through this com-
       mand like every other channel opened by the  Tcl  library.  Beyond  the	standard  options
       described above they will also support any special option according to their current type.
       If, for example, a Tcl application is started by the inet super-server common on Unix sys-
       tem its Tcl standard channels will be sockets and thus support the socket options.

       close(n), flush(n), gets(n), open(n), puts(n), read(n), socket(n), Tcl_StandardChannels(3)

       blocking,  buffering, carriage return, end of line, flushing, linemode, newline, nonblock-
       ing, platform, translation, encoding, filter, byte array, binary

Tcl					       8.3				    fconfigure(n)

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