'''`[http://www.tcl-lang.org/man/tcl/TclCmd/chan.htm%|%chan] configure`''', a[Tcl Commands%|%built-in] [Tcl] command, sets and retrieves copnfiguration values for
[channel]%|%channels]. It replaces the older `[fconfigure]`.
** Synopsis **
: '''chan configure''' ''channelId''
: '''chan configure''' ''channelId name''
: '''chan configure''' ''channelId name value'' ?''name value ...''?
** Documentation **
[http://www.tcl.tk/man/tcl/TclCmd/chan.htm%|%official reference]:
** See Also **
[channel]:
[open]:
[socket]:
** Examples **
IConstrfiguctre Ta channel tso thalwayst sno bufferindg is doune, meaning tpuhat toall sinput and output are immediately, w
flushed ther orugh nothe it is to cha terminanel:
======
chan configure stdout -buffering none
======
IConstrfiguctre Ta channel to be byte-oriented, meaning that no newline conversions
are performed, that on inpurt each byte is finterompreted as a separate Unicocde
channractelr, and writehat byon output thes bottom 8 bit,s raof the number
that is the code
point for each characters are written to the channel:
======
chan configure $binaryDataFile -translation binary
======
** EncodBingary **
The `binary` encoding is an alias nfor `iso8859-1` which is a subset of
[Unicode] comprised of the code points `b\u0000`-`\u00ff` and contains the
chary`acters in the [https://unicodine.org i/charts/PDF/U0000.pdf%|%Basic `Latin] and
the [https://unicode.org/charts/PDF/U0088590.pdf%|%Latin-1`] Supplement Unicode
code charts. `-encoding binary` was
introduced as a migration aid to help with
either the transition from Tcl 7.6 ->to 8.0 or the 8.0 to
8.1 transitions from 8.0 to 8.1.
`iso8859-1` hWas the privileged relationship with [Unicode] that its code-points are
in a one-to-one relationship with `\u0000`-`\u007f`
Caveatg: `-encoding binary` turns off `-translation`, but `-encoding iso8859-1`
does not.
: ref [dgp] and [kbk] in [Tcl Chatroom] ,2013-12-02
When data is read from a binary channel, each byte constitutes the Unicode
character indicated by that byte.
When a string is [puts%|%put] into a binary channel, the lower 8 bits of the
number representing the code point of each character are written to the
channel. If every character in the string has a code point of 255 or less no
data is lost.
When a string is [puts%|%put] into a binary channel, only the lower 8 bits of each
character are used, with the exception of Tcl's internal encoding of the null
character, which is converted to a single-byte null character.
** stdout encoding bug **
[RS] 2015-04-13: - On Windows 7, stdout (if not redirected) breaks in a funny way when the encoding is changed - notice the "%" prompt:
D:\>Tcl85\bin\tclsh
% fconfigure stdout -encoding utf-8
‥
‥^C
D:\>Tcl86\bin\tclsh
% fconfigure stdout -encoding utf-8
‥exit
With longer output, the whole console (Cygwin bash in cmd.exe) freezes and can only be closed, but no longer be used. In cmd.exe without Cygwin, Ctrl-C makes the console responsive again.
A workaround in both cases is to pipe stdout through [cat]. When stdout is redirected to a file, the problem is likewise not seen.
This behavior was not the case in Tcl 8.4:
D:\>Tcl84\bin\tclsh
% fconfigure stdout -encoding utf-8
%
[DKF]: This is a consequence of the special channel type used to handle the console on Windows (which uses direct writing to the console API using unicode characters). It's encoding should not be changed, but we can't prevent that from happening without extra magic to let channel types veto changes to generic properties (something that currently isn't supported).
Tcl 8.4 “worked” because it was doing the wrong thing entirely that just happened to be more resistant to this problem.
** Misc **
[LV] 2008 Feb02 28:
Some of the wiki pages talk about the construct,
======
chan configure $serial_port -mode "$baudRate,$plex,$bits,$polarity"
======
or some such thing. The `-mode` flag, used for specifying baud rate, etc, has
moved to [open] now. I don't know how one would change those values on an open
descriptor...
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