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

__________________________________________________________________________________________________________________________________________________

NAME

       fconfigure - Set and get options on a channel

SYNOPSIS

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

DESCRIPTION

       The  fconfigure command sets and retrieves options for channels.  ChannelId identifies the channel for which to set or query an option.	If
       no name or value arguments are supplied, the command returns a list containing alternating 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 nonblocking mode it
	      will affect the operation of the gets, read, puts, flush, and close commands; see the documentation for those commands for  details.
	      For nonblocking 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 buffer 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 character 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 setting is line.  Additionally, stdin
	      and stdout are intially 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  con- |
	      verted 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 interpretation 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 output when the channel
	      is closed.  If char is the empty string, then there is no special end of file character marker.  For read-write channels, a two-ele-
	      ment list specifies the end of file marker for input and output, respectively.  As a convenience, when setting the end-of-file char-
	      acter 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 character (
).  However, in actual files and devices
	      the end of a line may be represented differently on different platforms, or even for different devices on the  same  platform.   For
	      example, under UNIX newlines are used in files, whereas carriage-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  ele-
	      ment.   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 supported:

	      auto   As  the  input translation mode, auto treats any of newline (lf), carriage return (cr), or carriage return followed by a new-
		     line (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
		     sockets 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 Windows 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 character to the empty string (which disables it) and sets the encoding to binary (which disables encod- |
		     ing 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 single carriage return character.  As the input trans-
		     lation mode, cr mode converts 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 carriage return character followed by a linefeed char-
		     acter.  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 typi-
		     cally used on Windows platforms and for network connections.

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

SEE ALSO

       close(n), flush(n), gets(n), puts(n), read(n), socket(n)

KEYWORDS

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

Tcl									8.1							     fconfigure(n)