path: root/doc/fconfigure.n

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.so man.macros
.TH fconfigure n 8.3 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
fconfigure \- Set and get options on a channel
.SH SYNOPSIS
.nf
\fBfconfigure \fIchannelId\fR
\fBfconfigure \fIchannelId\fR \fIname\fR
\fBfconfigure \fIchannelId\fR \fIname value \fR?\fIname value ...\fR?
.fi
.BE
.SH DESCRIPTION
.PP
The \fBfconfigure\fR command sets and retrieves options for channels.
.PP
\fIChannelId\fR identifies the channel for which to set or query an
option and must refer to an open channel such as a Tcl standard
channel (\fBstdin\fR, \fBstdout\fR, or \fBstderr\fR), the return
value from an invocation of \fBopen\fR or \fBsocket\fR, or the result
of a channel creation command provided by a Tcl extension.
.PP
If no \fIname\fR or \fIvalue\fR arguments are supplied, the command
returns a list containing alternating option names and values for the channel.
If \fIname\fR is supplied but no \fIvalue\fR then the command returns
the current value of the given option.
If one or more pairs of \fIname\fR and \fIvalue\fR are supplied, the
command sets each of the named options to the corresponding \fIvalue\fR;
in this case the return value is an empty string.
.PP
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 \fBsocket\fR command for its additional options.
.TP
\fB\-blocking\fR \fIboolean\fR
The \fB\-blocking\fR 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 \fBgets\fR,
\fBread\fR, \fBputs\fR, \fBflush\fR, and \fBclose\fR 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 \fBTcl_DoOneEvent\fR or
invoking the \fBvwait\fR command).
.TP
\fB\-buffering\fR \fInewValue\fR
.
If \fInewValue\fR is \fBfull\fR then the I/O system will buffer output
until its internal buffer is full or until the \fBflush\fR command is
invoked. If \fInewValue\fR is \fBline\fR, then the I/O system will
automatically flush output for the channel whenever a newline character
is output. If \fInewValue\fR is \fBnone\fR, the I/O system will flush
automatically after every output operation.  The default is for
\fB\-buffering\fR to be set to \fBfull\fR except for channels that
connect to terminal-like devices; for these channels the initial setting
is \fBline\fR.  Additionally, \fBstdin\fR and \fBstdout\fR are
initially set to \fBline\fR, and \fBstderr\fR is set to \fBnone\fR.
.TP
\fB\-buffersize\fR \fInewSize\fR
.
\fINewvalue\fR 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. \fINewvalue\fR must be between ten and one million, allowing
buffers of ten to one million bytes in size.
.TP
\fB\-encoding\fR \fIname\fR
.
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 \fBshiftjis\fR
and properly process and display the contents, the encoding would be set
to \fBshiftjis\fR.  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.
.RS
.PP
If a file contains pure binary data (for instance, a JPEG image), the
encoding for the channel should be configured to be \fBbinary\fR.  Tcl
will then assign no interpretation to the data in the file and simply read or
write raw bytes.  The Tcl \fBbinary\fR command can be used to manipulate this
byte-oriented data.
.PP
The default encoding for newly opened channels is the same platform- and
locale-dependent system encoding used for interfacing with the operating
system.  
.RE
.TP
\fB\-eofchar\fR \fIchar\fR
.TP
\fB\-eofchar\fR \fB{\fIinChar outChar\fB}\fR
.
This option supports DOS file systems that use Control-z (\ex1a) as an
end of file marker.  If \fIchar\fR 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 \fIchar\fR is the empty string, then there is no special 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
convenience, 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 \fB\-eofchar\fR is the empty string in all cases except for files
under Windows.  In that case the \fB\-eofchar\fR is Control-z (\ex1a) for
reading and the empty string for writing.
.TP
\fB\-translation\fR \fImode\fR
.TP
\fB\-translation\fR \fB{\fIinMode outMode\fB}\fR 
.
In Tcl scripts the end of a line is always represented using a single
newline character (\en).  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 \fBgets\fP
and \fBread\fP) the Tcl I/O system automatically translates the external
end-of-line representation into newline characters.  Upon output (i.e.,
with \fBputs\fP), the I/O system translates newlines to the external
end-of-line representation.  The default translation mode, \fBauto\fP,
handles all the common cases automatically, but the \fB\-translation\fR
option provides explicit control over the end of line translations.
.RS
.PP
The value associated with \fB\-translation\fR 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 supported:
.TP
\fBauto\fR
.
As the input translation mode, \fBauto\fR treats any of newline
(\fBlf\fP), carriage return (\fBcr\fP), or carriage return followed by a
newline (\fBcrlf\fP) 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, \fBauto\fR
chooses a platform specific representation; for sockets on all platforms
Tcl chooses \fBcrlf\fR, for all Unix flavors, it chooses \fBlf\fR, for the
Macintosh platform it chooses \fBcr\fR and for the various flavors of
Windows it chooses \fBcrlf\fR.  The default setting for
\fB\-translation\fR is \fBauto\fR for both input and output.
.TP
\fBbinary\fR 
.
No end-of-line translations are performed.  This is nearly identical to
\fBlf\fP mode, except that in addition \fBbinary\fP mode also sets the
end-of-file character to the empty string (which disables it) and sets the
encoding to \fBbinary\fR (which disables encoding filtering).  See the
description of \fB\-eofchar\fR and \fB\-encoding\fR for more information.
.TP
\fBcr\fR
.
The end of a line in the underlying file or device is represented by a
single carriage return character.  As the input translation mode,
\fBcr\fP mode converts carriage returns to newline characters.  As the
output translation mode, \fBcr\fP mode translates newline characters to
carriage returns.  This mode is typically used on Macintosh platforms.
.TP
\fBcrlf\fR
.
The end of a line in the underlying file or device is represented by a
carriage return character followed by a linefeed character.  As the input
translation mode, \fBcrlf\fP mode converts carriage-return-linefeed
sequences to newline characters.  As the output translation mode,
\fBcrlf\fP mode translates newline characters to carriage-return-linefeed
sequences.  This mode is typically used on Windows platforms and for
network connections.
.TP
\fBlf\fR
.
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.
.RE
.PP

.SH "STANDARD CHANNELS"
.PP
The Tcl standard channels (\fBstdin\fR, \fBstdout\fR, and \fBstderr\fR)
can be configured through this command 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 \fBinet\fR
super-server common on Unix system its Tcl standard channels will be
sockets and thus support the socket options.

.VS 8.4
.SH "SERIAL PORT CONFIGURATION OPTIONS"
.PP
If \fIchannelId\fR refers to a serial port, then the following
additional configuration options are available on Windows and
Unix systems with a POSIX serial interface:

.TP
\fB\-mode\fR \fIbaud\fB,\fIparity\fB,\fIdata\fB,\fIstop\fR
.
This option is a set of 4 comma-separated values: the baud rate, parity,
number of data bits, and number of stop bits for this serial port.  The
\fIbaud\fR rate is a simple integer that specifies the connection speed.
\fIParity\fR is one of the following letters: \fBn\fR, \fBo\fR, \fBe\fR,
\fBm\fR, \fBs\fR; respectively signifying the parity options of ``none'',
``odd'', ``even'', ``mark'', or ``space''.  \fIData\fR is the number of
data bits and should be an integer from 5 to 8, while \fIstop\fR is the
number of stop bits and should be the integer 1 or 2.

.TP
\fB\-handshake\fR \fItype\fR
.
(Windows and Unix). This option is used to setup automatic handshake
control. Note that not all handshake types maybe supported by your operating
system. The \fItype\fR parameter is case-independent.

If \fItype\fR is \fBnone\fR then any handshake is switched off.
\fBrtscts\fR activates hardware handshake. Hardware handshake signals
are described below.
For software handshake \fBxonxoff\fR the handshake characters can be redefined
with \fB-xchar\fR.
An additional hardware handshake \fBdtrdsr\fR is available only under Windows.
There is no default handshake configuration, the initial value depends
on your operating system settings.
The \fB-handshake\fR option cannot be queried.

.TP
\fB\-queue\fR
.
(Windows and Unix). The \fB-queue\fR option can only be queried.
It returns a list of two integers representing the current number
of bytes in the input and output queue respectively.

.TP
\fB\-timeout\fR \fImsec\fR
.
(Windows and Unix). This option is used to set the timeout for blocking
read operations. It specifies the maximum interval between the
reception of two bytes in milliseconds.
For Unix systems the granularity is 100 milliseconds.
The \fB-timeout\fR option does not affect write operations or
nonblocking reads.
This option cannot be queried.

.TP
\fB\-ttycontrol\fR \fI{signal boolean signal boolean ...}\fR
.
(Windows and Unix). This option is used to setup the handshake
output lines (see below) permanently or to send a BREAK over the serial line.
The \fIsignal\fR names are case-independent.
\fB{RTS 1 DTR 0}\fR sets the RTS output to high and the DTR output to low.
The BREAK condition (see below) is enabled and disabled with \fB{BREAK 1}\fR and
\fB{BREAK 0}\fR respectively.
It's not a good idea to change the \fBRTS\fR (or \fBDTR\fR) signal
with active hardware handshake \fBrtscts\fR (or \fBdtrdsr\fR).
The result is unpredictable.
The \fB-ttycontrol\fR option cannot be queried.

.TP
\fB\-ttystatus\fR
.
(Windows and Unix). The \fB-ttystatus\fR option can only be
queried.  It returns the current modem status and handshake input signals
(see below).
The result is a list of signal,value pairs with a fixed order,
e.g. \fB{CTS 1 DSR 0 RING 1 DCD 0}\fR.
The \fIsignal\fR names are returned upper case.

.TP
\fB\-xchar\fR \fI{xonChar xoffChar}\fR
.
(Windows and Unix). This option is used to query or change the software
handshake characters. Normally the operating system default should be
DC1 (0x11) and DC3 (0x13) representing the ASCII standard
XON and XOFF characters.

.TP
\fB\-pollinterval\fR \fImsec\fR
.
(Windows only). This option is used to set the maximum time between
polling for fileevents.
This affects the time interval between checking for events throughout the Tcl
interpreter (the smallest value always wins).  Use this option only if
you want to poll the serial port more or less often than 10 msec
(the default).

.TP
\fB\-sysbuffer\fR \fIinSize\fR
.TP
\fB\-sysbuffer\fR \fI{inSize outSize}\fR
.
(Windows only). This option is used to change the size of Windows
system buffers for a serial channel. Especially at higher communication
rates the default input buffer size of 4096 bytes can overrun
for latent systems. The first form specifies the input buffer size,
in the second form both input and output buffers are defined.

.TP
\fB\-lasterror\fR
.
(Windows only). This option is query only.
In case of a serial communication error, \fBread\fR or \fBputs\fR
returns a general Tcl file I/O error.
\fBfconfigure -lasterror\fR can be called to get a list of error details.
See below for an explanation of the various error codes.

.SH "SERIAL PORT SIGNALS"
.PP
RS-232 is the most commonly used standard electrical interface for serial
communications. A negative voltage (-3V..-12V) define a mark (on=1) bit and
a positive voltage (+3..+12V) define a space (off=0) bit (RS-232C).  The
following signals are specified for incoming and outgoing data, status
lines and handshaking. Here we are using the terms \fIworkstation\fR for
your computer and \fImodem\fR for the external device, because some signal
names (DCD, RI) come from modems. Of course your external device may use
these signal lines for other purposes.
.RS
.IP \fBTXD(output)\fR
\fBTransmitted Data:\fR Outgoing serial data.
.IP \fBRXD(input)\fR
\fBReceived Data:\fRIncoming serial data.
.IP \fBRTS(output)\fR
\fBRequest To Send:\fR This hardware handshake line informs the modem that
your workstation is ready to receive data. Your workstation may
automatically reset this signal to indicate that the input buffer is full.
.IP \fBCTS(input)\fR
\fBClear To Send:\fR The complement to RTS. Indicates that the modem is
ready to receive data.
.IP \fBDTR(output)\fR
\fBData Terminal Ready:\fR This signal tells the modem that the workstation
is ready to establish a link. DTR is often enabled automatically whenever a
serial port is opened.
.IP \fBDSR(input)\fR
\fBData Set Ready:\fR The complement to DTR. Tells the workstation that the
modem is ready to establish a link.
.IP \fBDCD(input)\fR
\fBData Carrier Detect:\fR This line becomes active when a modem detects
a "Carrier" signal.
.IP \fBRI(input)\fR
\fBRing Indicator:\fR Goes active when the modem detects an incoming call.
.IP \fBBREAK\fR
A BREAK condition is not a hardware signal line, but a logical zero on the
TXD or RXD lines for a long period of time, usually 250 to 500
milliseconds.  Normally a receive or transmit data signal stays at the mark
(on=1) voltage until the next character is transferred. A BREAK is sometimes
used to reset the communications line or change the operating mode of
communications hardware.
.RE

.SH "ERROR CODES (Windows only)"
.PP
A lot of different errors may occur during serial read operations or during
event polling in background. The external device may have been switched
off, the data lines may be noisy, system buffers may overrun or your mode
settings may be wrong.  That's why a reliable software should always
\fBcatch\fR serial read operations.  In cases of an error Tcl returns a
general file I/O error.  Then \fBfconfigure -lasterror\fR may help to
locate the problem.  The following error codes may be returned.
.RS
.IP \fBRXOVER:\fR
Windows input buffer overrun. The data comes faster than your scripts reads
it or your system is overloaded. Use \fBfconfigure -sysbuffer\fR to avoid a
temporary bottleneck and/or make your script faster.
.IP \fBTXFULL\fR
Windows output buffer overrun. Complement to RXOVER. This error should
practically not happen, because Tcl cares about the output buffer status.
.IP \fBOVERRUN\fR
UART buffer overrun (hardware) with data lost.
The data comes faster than the system driver receives it.
Check your advanced serial port settings to enable the FIFO (16550) buffer
and/or setup a lower(1) interrupt threshold value.
.IP \fBRXPARITY\fR
A parity error has been detected by your UART.
Wrong parity settings with \fBfconfigure -mode\fR or a noisy data line (RXD)
may cause this error.
.IP \fBFRAME\fR
A stop-bit error has been detected by your UART.
Wrong mode settings with \fBfconfigure -mode\fR or a noisy data line (RXD)
may cause this error.
.IP \fBBREAK\fR
A BREAK condition has been detected by your UART (see above).
.RE
.VE

.SH "SEE ALSO"
close(n), flush(n), gets(n), puts(n), read(n), socket(n),
Tcl_StandardChannels(3)

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