unix/dltest/*.o
unix/dltest/*.sl
unix/dltest/*.so
unix/tcl.pc
unix/tclIndex
unix/Tcl-Info.plist
unix/Tclsh-Info.plist
unix/pkgs8/*
unix/pkgs/*
win/Debug*
win/Release*
win/*.manifest
win/pkgs8/*
win/pkgs/*
win/coffbase.txt
win/tcl.hpj
win/nmakehlp.out
win/nmhlp-out.txt

jobs:
  gcc:
    runs-on: ubuntu-22.04
    strategy:
      matrix:
        config:
          - ""
          - "CFLAGS=-DTCL_NO_DEPRECATED=1"
          - "--disable-shared"
          - "--disable-zipfs"
          - "--enable-symbols"
          - "--enable-symbols=mem"
          - "--enable-symbols=all"
          - "CFLAGS=-ftrapv"
          # Duplicated below

      run:
        shell: msys2 {0}
        working-directory: win
    strategy:
      matrix:
        config:
          - ""
          - "CFLAGS=-DTCL_NO_DEPRECATED=1"
          - "--disable-shared"
          - "--disable-zipfs"
          - "--enable-symbols"
          - "--enable-symbols=mem"
          - "--enable-symbols=all"
    # Using powershell means we need to explicitly stop on failure
    steps:

libtommath/*.tex
macosx/configure
unix/autoMkindex.tcl
unix/dltest.marker
unix/dltest/embtest
unix/tcl.pc
unix/tclIndex
unix/pkgs8/*
unix/pkgs/*
win/Debug*
win/Release*
win/*.manifest
win/pkgs8/*
win/pkgs/*
win/coffbase.txt
win/tcl.hpj
win/nmakehlp.out
win/nmhlp-out.txt

                    GNU AFFERO GENERAL PUBLIC LICENSE
                       Version 3, 19 November 2007

 Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
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  If the Program specifies that a proxy can decide which future
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  16. Limitation of Liability.

  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
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THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
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  17. Interpretation of Sections 15 and 16.

  If the disclaimer of warranty and limitation of liability provided
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reviewing courts shall apply local law that most closely approximates
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                     END OF TERMS AND CONDITIONS

            How to Apply These Terms to Your New Programs

  If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.

  To do so, attach the following notices to the program.  It is safest
to attach them to the start of each source file to most effectively
state the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.

    <one line to give the program's name and a brief idea of what it does.>
    Copyright (C) <year>  <name of author>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.

Also add information on how to contact you by electronic and paper mail.

  If your software can interact with users remotely through a computer
network, you should also make sure that it provides a way for users to
get its source.  For example, if your program is a web application, its
interface could display a "Source" link that leads users to an archive
of the code.  There are many ways you could offer source, and different
solutions will be better for different programs; see section 13 for the
specific requirements.

  You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU AGPL, see
<https://www.gnu.org/licenses/>.

# README:  Tcl

This is the **Tcl 9.0.1** source distribution.
This is the **Tcl Unchained 9.0.1** source distribution.

You can get any source release of Tcl from [our distribution
site](https://sourceforge.net/projects/tcl/files/Tcl/).

9.0 (production release, daily build)
[![Build Status](https://github.com/tcltk/tcl/actions/workflows/linux-build.yml/badge.svg?branch=main)](https://github.com/tcltk/tcl/actions/workflows/linux-build.yml?query=branch%3Amain)
[![Build Status](https://github.com/tcltk/tcl/actions/workflows/win-build.yml/badge.svg?branch=main)](https://github.com/tcltk/tcl/actions/workflows/win-build.yml?query=branch%3Amain)

/*
 * dlfcn.h --
 *
 *	This file provides a replacement for the header file "dlfcn.h"
 *	on systems where dlfcn.h is missing.  It's primary use is for
 *	AIX, where Tcl emulates the dl library.
 *
 *	This file is subject to the following copyright notice, which is
 *	different from the notice used elsewhere in Tcl but rougly
 *	equivalent in meaning.
 *
 *	Copyright (c) 1992,1993,1995,1996, Jens-Uwe Mager, Helios Software GmbH
 *	Not derived from licensed software.
 *
 *	Permission is granted to freely use, copy, modify, and redistribute
 *	this software, provided that the author is not construed to be liable
 *	for any results of using the software, alterations are clearly marked
 *	as such, and this notice is not modified.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

/*
 * dlfcn.h --
 *
 *	This file provides a replacement for the header file "dlfcn.h"
 *	on systems where dlfcn.h is missing.  It's primary use is for
 *	AIX, where Tcl emulates the dl library.
 *
 * This is an unpublished work copyright (c) 1992 HELIOS Software GmbH
 * 30159 Hannover, Germany
 */

#ifndef __dlfcn_h__
#define __dlfcn_h__

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

/*
 * Pseudo-implementation of RFC2553 name / address resolution functions
 *
 * But these functions are not implemented correctly. The minimum subset
 * is implemented for ssh use only. For example, this routine assumes
 * that ai_family is AF_INET. Don't use it for another purpose.

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.

 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

/*
 * Pseudo-implementation of RFC2553 name / address resolution functions
 *
 * But these functions are not implemented correctly. The minimum subset
 * is implemented for ssh use only. For example, this routine assumes
 * that ai_family is AF_INET. Don't use it for another purpose.

/*
 * gettod.c --
 *
 *	This file provides the gettimeofday function on systems
 *	that only have the System V ftime function.
 *
 * Copyright (c) 1995 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.

 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

/*
 * gettod.c --
 *
 *	This file provides the gettimeofday function on systems
 *	that only have the System V ftime function.
 *
*/

#include "tclPort.h"
#include <sys/timeb.h>

#undef timezone

int

/*
 * mkstemp.c --
 *
 *	Source code for the "mkstemp" library routine.
 *
 * Copyright (c) 2009 Donal K. Fellows
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.

 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

/*
 * strncasecmp.c --
 *
 *	Source code for the "strncasecmp" library routine.
 *
 * Copyright (c) 1988-1993 The Regents of the University of California.
 * Copyright (c) 1995-1996 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.

 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

#include "tclPort.h"

/*
 * This array is designed for mapping upper and lower case letter together for
 * a case independent comparison. The mappings are based upon ASCII character
 * sequences.

/*
 * waitpid.c --
 *
 *	This procedure emulates the POSIX waitpid kernel call on BSD systems
 *	that don't have waitpid but do have wait3. This code is based on a
 *	prototype version written by Mark Diekhans and Karl Lehenbauer.
 *
 * Copyright (c) 1993 The Regents of the University of California.
 * Copyright (c) 1994 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 */

/*
 * You may distribute and/or modify this program under the terms of the GNU
 * Affero General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.

 * See the file "COPYING" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/

#include "tclPort.h"

#ifndef pid_t
#define pid_t int
#endif

'\"
'\" Copyright (c) 1998-1999 Scriptics Corporation
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_Access 3 8.1 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_Access, Tcl_Stat \- check file permissions and other attributes
.SH SYNOPSIS

'\"
'\" Copyright (c) 1989-1993 The Regents of the University of California.
'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_AddErrorInfo 3 8.5 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_GetReturnOptions, Tcl_SetReturnOptions, Tcl_AddErrorInfo, Tcl_AppendObjToErrorInfo, Tcl_AddObjErrorInfo, Tcl_SetObjErrorCode, Tcl_SetErrorCode, Tcl_SetErrorLine, Tcl_GetErrorLine, Tcl_PosixError, Tcl_LogCommandInfo \- retrieve or record information about errors and other return options
.SH SYNOPSIS

'\"
'\" Copyright (c) 1995-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_Alloc 3 9.0 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_Alloc, Tcl_Free, Tcl_Realloc, Tcl_AttemptAlloc, Tcl_AttemptRealloc, Tcl_GetMemoryInfo \- allocate or free heap memory
.SH SYNOPSIS

'\"
'\" Copyright (c) 1989-1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_AllowExceptions 3 7.4 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_AllowExceptions \- allow all exceptions in next script evaluation
.SH SYNOPSIS

'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_AppInit 3 7.0 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_AppInit \- perform application-specific initialization
.SH SYNOPSIS

converted. \fBTCL_ENCODING_END\fR signifies that the source buffer is the last
block in a (potentially multi-block) input stream, telling the conversion
routine to perform any finalization that needs to occur after the last
byte is converted and then to reset to an initial state. The
\fBTCL_PROFILE_*\fR bits defined in the \fBPROFILES\fR section below
control the encoding profile to be used for dealing with invalid data or
other errors in the encoding transform.
The flag \fBTCL_ENCODING_STOPONERROR\fR has no effect,
it only has meaning in Tcl 8.x.
.PP
Some flags bits may not be usable with some functions as noted in the
function descriptions below.
.AP Tcl_EncodingState *statePtr in/out
Used when converting a (generally long or indefinite length) byte stream
in a piece-by-piece fashion.  The conversion routine stores its current
state in \fI*statePtr\fR after \fIsrc\fR (the buffer containing the
current piece) has been converted; that state information must be passed

.PP
.CS
.ta 1.5i
# Encoding file: iso2022-jp, escape-driven
E
init		{}
final		{}
iso8859-1	\ex1B(B
jis0201		\ex1B(J
jis0208		\ex1B$@
jis0208		\ex1B$B
jis0212		\ex1B$(D
gb2312		\ex1B$A
ksc5601		\ex1B$(C
iso8859-1	\ex1b(B
jis0201		\ex1b(J
jis0208		\ex1b$@
jis0208		\ex1b$B
jis0212		\ex1b$(D
gb2312		\ex1b$A
ksc5601		\ex1b$(C
.CE
.PP
In the file, the first column represents an option and the second column
is the associated value.  \fBinit\fR is a string to emit or expect before
the first character is converted, while \fBfinal\fR is a string to emit
or expect after the last character.  All other options are names of
table-based encodings; the associated value is the escape-sequence that
marks that encoding.  Tcl syntax is used for the values; in the above
example, for instance,
.QW \fB{}\fR
represents the empty string and
.QW \fB\ex1B\fR
.QW \fB\ex1b\fR
represents character 27.
.PP
When \fBTcl_GetEncoding\fR encounters an encoding \fIname\fR that has not
been loaded, it attempts to load an encoding file called \fIname\fB.enc\fR
from the \fBencoding\fR subdirectory of each directory that Tcl searches
for its script library.  If the encoding file exists, but is
malformed, an error message will be left in \fIinterp\fR.

Encoding profiles define the manner in which errors in the encoding transforms
are handled by the encoding functions. An application can specify the profile
to be used by OR-ing the \fBflags\fR parameter passed to the function
with at most one of \fBTCL_ENCODING_PROFILE_TCL8\fR,
\fBTCL_ENCODING_PROFILE_STRICT\fR or \fBTCL_ENCODING_PROFILE_REPLACE\fR.
These correspond to the \fBtcl8\fR, \fBstrict\fR and \fBreplace\fR profiles
respectively. If none are specified, a version-dependent default profile is used.
For Tcl 9.0, the default profile is \fBstrict\fR.
The default profile is \fBstrict\fR.
.PP
For details about profiles, see the \fBPROFILES\fR section in
the documentation of the \fBencoding\fR command.
.SH "SEE ALSO"
encoding(n)
.SH KEYWORDS
utf, encoding, convert

'\"
'\" Copyright (c) 1996-1997 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_ObjType 3 9.0 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_RegisterObjType, Tcl_GetObjType, Tcl_AppendAllObjTypes, Tcl_ConvertToType, Tcl_FreeInternalRep, Tcl_InitStringRep, Tcl_HasStringRep, Tcl_StoreInternalRep, Tcl_FetchInternalRep  \- manipulate Tcl value types
Tcl_RegisterObjType, Tcl_GetObjType, Tcl_AppendAllObjTypes, Tcl_ConvertToType
	,Tcl_FreeInternalRep, Tcl_InitStringRep, Tcl_HasStringRep
	,Tcl_NewObjInterface, Tcl_NewObjType
	, Tcl_StoreInternalRep, Tcl_FetchInternalRep  \- manipulate Tcl value types
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
\fBTcl_RegisterObjType\fR(\fItypePtr\fR)
.sp
const Tcl_ObjType *

.sp
char *
\fBTcl_InitStringRep\fR(\fIobjPtr, bytes, numBytes\fR)
.sp
int
\fBTcl_HasStringRep\fR(\fIobjPtr\fR)
.sp
Tcl_ObjInterface *
Tcl_NewObjInterface()
.sp
Tcl_ObjType *
\fBTcl_NewObjType\fR()
.sp
void
\fBTcl_StoreInternalRep\fR(\fIobjPtr, typePtr, irPtr\fR)
.sp
Tcl_ObjInternalRep *
\fBTcl_FetchInternalRep\fR(\fIobjPtr, typePtr\fR)
.fi
.SH ARGUMENTS

.SH DESCRIPTION
.PP
The procedures in this man page manage Tcl value types (sometimes
referred to as object types or \fBTcl_ObjType\fRs for historical reasons).
They are used to register new value types, look up types,
and force conversions from one type to another.
.PP
\fBTcl_NewObjType\fR allocates a new \fBTcl_ObjType\fR and returns a
pointer to it.
.PP
\fBTcl_NewObjInterface\fR allocates a new \fBTcl_ObjInterface\fR and returns a
pointer to it.
.PP
\fBTcl_ObjTypeSetInterface\fR sets the given \fBTcl_ObjInterface\fB for the
given \fBTcl_ObjType\fR.
.PP
\fBTcl_RegisterObjType\fR registers a new Tcl value type
in the table of all value types that \fBTcl_GetObjType\fR
can look up by name.  There are other value types supported by Tcl
as well, which Tcl chooses not to register.  Extensions can likewise
choose to register the value types they create or not.
The argument \fItypePtr\fR points to a Tcl_ObjType structure that

.CE
where the contents are exactly the existing contents of the union in the
\fIinternalRep\fR field of the \fITcl_Obj\fR struct.
This definition permits us to pass internal representations and pointers to
them as arguments and results in public routines.
.SH "THE TCL_OBJTYPE STRUCTURE"
.PP
Extension writers can define new value types by defining four to twelve
Extension writers can define new value types by defining procedures for the
procedures and initializing a Tcl_ObjType structure to describe the
type.  Extension writers may also pass a pointer to their Tcl_ObjType
structure to \fBTcl_RegisterObjType\fR if they wish to permit other
extensions to look up their Tcl_ObjType by name with the
\fBTcl_GetObjType\fR routine.  The \fBTcl_ObjType\fR structure is
defined as follows:
funtion types described below.  An extension may also pass to
\fBTcl_RegisterObjType\fR a pointer to a custom Tcl_ObjType structure in order
to permit other extensions to look up the Tcl_ObjType by name with the
\fBTcl_GetObjType\fR routine.  The \fBTcl_ObjType\fR structure is defined as
follows:
.PP
.CS
typedef struct {
    const char *\fIname\fR;
    Tcl_FreeInternalRepProc *\fIfreeIntRepProc\fR;
    Tcl_DupInternalRepProc *\fIdupIntRepProc\fR;
    Tcl_UpdateStringProc *\fIupdateStringProc\fR;
    Tcl_SetFromAnyProc *\fIsetFromAnyProc\fR;
    size_t \fIversion\fR;
    /* List emulation functions - ObjType Version 1 & 2 */
    Tcl_ObjTypeLengthProc *lengthProc;
    /* List emulation functions - ObjType Version 2 */
    Tcl_ObjTypeIndexProc *\fIindexProc\fR;
    Tcl_ObjTypeSliceProc *\fIsliceProc\fR;
    Tcl_ObjTypeReverseProc *\fIreverseProc\fR;
    Tcl_ObjTypeGetElements *\fIgetElementsProc\fR;
    Tcl_ObjTypeSetElement *\fIsetElementProc\fR;
    Tcl_ObjTypeReplaceProc *\fIreplaceProc\fR;
    Tcl_ObjTypeInOperatorProc *\fIinOperProc\fR;
} \fBTcl_ObjType\fR;
.CE
.SS "THE NAME FIELD"
.PP
The \fIname\fR member describes the name of the type, e.g. \fBint\fR.
When a type is registered, this is the name used by callers
of \fBTcl_GetObjType\fR to lookup the type.  For unregistered

Note that if a subsidiary value has its reference count reduced to zero
during the running of a \fIfreeIntRepProc\fR, that value may be not freed
immediately, in order to limit stack usage. However, the value will be freed
before the outermost current \fBTcl_DecrRefCount\fR returns.
.SS "THE VERSION FIELD"
.PP
The \fIversion\fR member provides for future extensibility of the
structure and should be set to \fBTCL_OBJTYPE_V0\fR for compatibility
structure and should be set to 0 for compatibility
of ObjType definitions prior to version 9.0. Specifics about versions
will be described further in the sections below.
.SH "ABSTRACT LIST TYPES"
.SH "OTHER OPERATIONS"
.PP
Additional fields in the Tcl_ObjType descriptor allow for control over
A procedure for each of the type definitions below may be registered for
how custom data values can be manipulated using Tcl's List commands
without converting the value to a List type. This requires the custom
type to provide functions that will perform the given operation on the
custom data representation.  Not all functions are required. In the
absence of a particular function (set to NULL), the fallback is to
allow the internal List operation to perform the operation, most
applying an operation to the Tcl_Obj value.  For example, if a function of type
likely causing the value type to be converted to a traditional list.
.SS "SCALAR VALUE TYPES"
.PP
For a custom value type that is scalar or atomic in nature, i.e., not
a divisible collection, version \fBTCL_OBJTYPE_V1\fR is
recommended. In this case, List commands will treat the scalar value
as if it where a list of length 1, and not convert the value to a List
type.
.SS "VERSION 2: ABSTRACT LISTS"
.PP
Version 2, \fBTCL_OBJTYPE_V2\fR, allows full List support when the
functions described below are provided.  This allows for script level
use of the List commands without causing the type of the Tcl_Obj value
\fITcl_ObjInterfaceStringLengthProc\fR is registered, then if provides the
length of the string representation of the value.  If a function of type
to be converted to a list.
.SS "THE LENGTHPROC FIELD"
.PP
The \fBLengthProc\fR function correlates with the \fBTcl_ListObjLength\fR
C API. The function returns the number of elements in the list. It
\fITcl_ObjInterfaceListLengthProc\fR is registered, then it provides the number
of items in the list represented by the value.  It is not necessary to
is used in every List operation and is required for all Abstract List
implementations.
implement all procedures.  If a particular procedure is NULL, Tcl attempts
.CS
typedef Tcl_Size
to interpret the value as a type which supports the requested operation.  For
example, to perform a list index operation, The Tcl_Obj may be interpreted as
\fBtclListType\fR if possible.
(Tcl_ObjTypeLengthProc) (Tcl_Obj *listPtr);
.CE
.PP
.SS "THE INDEXPROC FIELD"
.PP
The \fBIndexProc\fR function correlates with with the
\fBTcl_ListObjIndex\fR C API. The function returns a Tcl_Obj value for
the element at the specified index.
.CS
typedef int (\fBTcl_ObjTypeIndexProc\fR) (
See the following typedef lines in
    Tcl_Interp *interp,
    Tcl_Obj *listPtr,
    Tcl_Size index,
    Tcl_Obj** elemObj);
.CE
.cs
.SS "THE SLICEPROC FIELD"
.PP
tcl.h
The \fBSliceProc\fR correlates with the \fBlrange\fR command,
returning a new List or Abstract List for the portion of the original
list specified.
.CS
.ce
typedef int (\fBTcl_ObjTypeSliceProc\fR) (
    Tcl_Interp *interp,
    Tcl_Obj *listPtr,
for the procedures that may registered.
    Tcl_Size fromIdx,
    Tcl_Size toIdx,
    Tcl_Obj **newObjPtr);
.CE
.SS "THE REVERSEPROC FIELD"
.PP
The \fBReverseProc\fR correlates with the \fBlreverse\fR command,
returning a List or Abstract List that has the same elements as the

.RS
list operations
input Abstract List, with the elements in the reverse order.
.RS
.CS
typedef int (\fBTcl_ObjTypeReverseProc\fR) (
    Tcl_Interp *interp,
    Tcl_Obj *listPtr,
    Tcl_Obj **newObjPtr);
Tcl_ObjInterfaceListAllProc
Tcl_ObjInterfaceListAppendProc
Tcl_ObjInterfaceListAppendlistProc
Tcl_ObjInterfaceListContainsProc
.CE
.SS "THE GETELEMENTS FIELD"
.PP
The \fBGetElements\fR function returns a count and a pointer to an
array of Tcl_Obj values for the entire Abstract List. This
Tcl_ObjInterfaceListIndexProc
correlates to the \fBTcl_ListObjGetElements\fR C API call.
.CS
typedef int (\fBTcl_ObjTypeGetElements\fR) (
    Tcl_Interp *interp,
    Tcl_Obj *listPtr,
    Tcl_Size *objcptr,
    Tcl_Obj ***objvptr);
Tcl_ObjInterfaceListIndexEndProc
Tcl_ObjInterfaceListIsSortedProc
Tcl_ObjInterfaceListLengthProc
Tcl_ObjInterfaceListRangeProc
Tcl_ObjInterfaceListRangeEndProc
.CE
.SS "THE SETELEMENT FIELD"
.PP
The \fBSetElement\fR function replaces the element within the
specified list at the give index. This function correlates to the
\fBlset\fR command.
.CS
typedef Tcl_Obj *(\fBTcl_ObjTypeSetElement\fR) (
    Tcl_Interp *interp,
    Tcl_Obj *listPtr,
Tcl_ObjInterfaceListReplaceProc
Tcl_ObjInterfaceListReplaceListProc
Tcl_ObjInterfaceListReverseProc
    Tcl_Size indexCount,
    Tcl_Obj *const indexArray[],
    Tcl_Obj *valueObj);
Tcl_ObjInterfaceListSetProc
Tcl_ObjInterfaceListSetDeepProc
.CE
.SS "REPLACEPROC FIELD"
.PP
The \fBReplaceProc\fR returns a new list after modifying the list
replacing the elements to be deleted, and adding the elements to be
.RE

string operations
inserted. This function correlates to the \fBTcl_ListObjReplace\fR C API.
.RS
.CS
typedef int (\fBTcl_ObjTypeReplaceProc\fR) (
    Tcl_Interp *interp,
    Tcl_Obj *listObj,
    Tcl_Size first,
    Tcl_Size numToDelete,
Tcl_ObjInterfaceStringIndexProc
Tcl_ObjInterfaceStringIndexEndProc
Tcl_ObjInterfaceStringIsEmptyProc
Tcl_ObjInterfaceStringLengthProc
Tcl_ObjInterfaceStringRangeProc
    Tcl_Size numToInsert,
    Tcl_Obj *const insertObjs[]);
Tcl_ObjInterfaceStringRangeEndProc
.CE
.SS "THE INOPERPROC FIELD"
.PP
.RE
The \fBInOperProc\fR function determines whether the value is present in the
given list, according to equivalent string comparison of elements. The
\fBboolResult\fR is set to 1 (true) if the value is present, and 0
(false) if it is not present. This function implements the "in" and
"ni" math operators for an abstract list.
.CS
typedef int (\fBTcl_ObjTypeInOperatorProc\fR) (
.RE

    Tcl_Interp *interp,
    Tcl_Obj *valueObj,
    Tcl_Obj *listObj,
    int *boolResult);
.CE
.SH "REFERENCE COUNT MANAGEMENT"
.PP
The \fIobjPtr\fR argument to \fBTcl_AppendAllObjTypes\fR should be an unshared
value; this function will not modify the reference count of that value, but
will modify its contents. If \fIobjPtr\fR is not (interpretable as) a list,
this function will set the interpreter result and produce an error; using an
unshared empty value is strongly recommended.

'\"
'\" Copyright (c) 1997 Sun Microsystems, Inc.
'\" Contributions from Don Porter, NIST, 2004. (not subject to US copyright)
'\" Copyright (c) 2018 Nathan Coulter.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_SaveInterpState 3 8.1 Tcl "Tcl Library Procedures"
.so man.macros
.BS
.SH NAME
Tcl_SaveInterpState, Tcl_RestoreInterpState, Tcl_DiscardInterpState \- save and restore an interpreter's state
Tcl_SaveInterpState, Tcl_RestoreInterpState, Tcl_DiscardInterpState \- Save and restore the
state of an an interpreter.
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_InterpState
\fBTcl_SaveInterpState\fR(\fIinterp, status\fR)
.sp
int
\fBTcl_RestoreInterpState\fR(\fIinterp, state\fR)
.sp
\fBTcl_DiscardInterpState\fR(\fIstate\fR)
.fi
.SH ARGUMENTS
.AS Tcl_InterpState savedPtr
.AP Tcl_Interp *interp in
Interpreter for which state should be saved.
The interpreter for the operation.
.AP int status in
Return code value to save as part of interpreter state.
The return code for the state.
.AP Tcl_InterpState state in
Saved state token to be restored or discarded.
A token for saved state.
.BE
.SH DESCRIPTION
.PP
These routines allows a C procedure to take a snapshot of the current
state of an interpreter so that it can be restored after a call
to \fBTcl_Eval\fR or some other routine that modifies the interpreter
These routines save the state of an interpreter before a call to a routine such
as \fBTcl_Eval\fR, and restore the state afterwards.
state.
.PP
\fBTcl_SaveInterpState\fR stores a snapshot of the interpreter state in
\fBTcl_SaveInterpState\fR saves the parts of \fIinterp\fR that comprise the
an opaque token returned by \fBTcl_SaveInterpState\fR.  That token
value may then be passed back to one of \fBTcl_RestoreInterpState\fR
or \fBTcl_DiscardInterpState\fR, depending on whether the interp
state is to be restored.  So long as one of the latter two routines
is called, Tcl will take care of memory management.
.PP
\fBTcl_SaveInterpState\fR takes a snapshot of those portions of
interpreter state that make up the full result of script evaluation.
This include the interpreter result, the return code (passed in
as the \fIstatus\fR argument, and any return options, including
\fB\-errorinfo\fR and \fB\-errorcode\fR when an error is in progress.
result of a script, including the resulting value, the return code passed as
\fIstatus\fR, and any options such as \fB\-errorinfo\fR and \fB\-errorcode\fR.
This snapshot is returned as an opaque token of type \fBTcl_InterpState\fR.
The call to \fBTcl_SaveInterpState\fR does not itself change the
state of the interpreter.
It returns a token for the saved state.  The interpreter result is not reset
and no interpreter state is changed.
.PP
\fBTcl_RestoreInterpState\fR accepts a \fBTcl_InterpState\fR token
\fBTcl_RestoreInterpState\fR restores the state indicated by \fIstate\fR and
previously returned by \fBTcl_SaveInterpState\fR and restores the
state of the interp to the state held in that snapshot.  The return
value of \fBTcl_RestoreInterpState\fR is the status value originally
passed to \fBTcl_SaveInterpState\fR when the snapshot token was
returns the \fIstatus\fR originally passed in the corresponding call to
\fBTcl_SaveInterpState\fR.
created.
.PP
\fBTcl_DiscardInterpState\fR is called to release a \fBTcl_InterpState\fR
token previously returned by \fBTcl_SaveInterpState\fR when that
snapshot is not to be restored to an interp.
.PP
The \fBTcl_InterpState\fR token returned by \fBTcl_SaveInterpState\fR
must eventually be passed to either \fBTcl_RestoreInterpState\fR
or \fBTcl_DiscardInterpState\fR to avoid a memory leak.  Once
If a saved state is not restored, \fBTcl_DiscardInterpState\fR must be called
the \fBTcl_InterpState\fR token is passed to one of them, the
token is no longer valid and should not be used anymore.
to release it.  A token used to discard or restore state must not be used
again.
.SH KEYWORDS
result, state, interp

\fBTcl_TransferResult\fR(\fIsourceInterp, code, targetInterp\fR)
.sp
\fBTcl_AppendElement\fR(\fIinterp, element\fR)
.fi
.SH ARGUMENTS
.AS Tcl_FreeProc sourceInterp out
.AP Tcl_Interp *interp out
Interpreter whose result is to be modified or read.
The interpreter get or set the result for.
.AP Tcl_Obj *objPtr in
Tcl value to become result for \fIinterp\fR.
A value to set the result to.
.AP char *result in
String value to become result for \fIinterp\fR or to be
appended to the existing result.
The string value set the result to, or to append to the existing result.
.AP "const char" *element in
String value to append as a list element
The string value to append as a list element
to the existing result of \fIinterp\fR.
.AP Tcl_FreeProc *freeProc in
Address of procedure to call to release storage at
\fIresult\fR, or \fBTCL_STATIC\fR, \fBTCL_DYNAMIC\fR, or
Pointer to a procedure to call to release storage at
\fIresult\fR.
\fBTCL_VOLATILE\fR.
.AP Tcl_Interp *sourceInterp in
Interpreter that the result and return options should be transferred from.
The interpreter to transfer the result and return options from.
.AP Tcl_Interp *targetInterp in
Interpreter that the result and return options should be transferred to.
The interpreter to transfer the result and return options to.
.AP int code in
Return code value that controls transfer of return options.
.BE
.SH DESCRIPTION
.PP
The procedures described here are utilities for manipulating the
result value in a Tcl interpreter.
These procedures manipulate the result of an interpreter.  Some procedures
provide a Tcl_Obj interface while others provide a string interface.  For
The interpreter result may be either a Tcl value or a string.
For example, \fBTcl_SetObjResult\fR and \fBTcl_SetResult\fR
example, \fBTcl_SetObjResult\fR accepts a Tcl_Obj and \fBTcl_SetResult\fR
set the interpreter result to, respectively, a value and a string.
Similarly, \fBTcl_GetObjResult\fR and \fBTcl_GetStringResult\fR
accepts a char *.  Similarly, \fBTcl_GetObjResult\fR produces a Tcl_Obj * and
return the interpreter result as a value and as a string.
The procedures always keep the string and value forms
\fBTcl_GetStringResult\fR produces a char *.  The procedures can be mixed and
of the interpreter result consistent.
For example, if \fBTcl_SetObjResult\fR is called to set
matched.  For example, if \fBTcl_SetObjResult\fR is called to set the result to
the result to a value,
then \fBTcl_GetStringResult\fR is called,
a Tcl_Obj value, and then \fBTcl_GetStringResult\fR is called, it returns a
it will return the value's string representation.
char * (but see caveats below).
.PP
\fBTcl_SetObjResult\fR
\fBTcl_SetObjResult\fR sets \fIobjPtr\fR as the result for \fIinterp\fR,
arranges for \fIobjPtr\fR to be the result for \fIinterp\fR,
replacing any existing result.
The result is left pointing to the value
referenced by \fIobjPtr\fR.
\fIobjPtr\fR's reference count is incremented
since there is now a new reference to it from \fIinterp\fR.
The reference count for any old result value
is decremented and the old result value is freed if no
references to it remain.
.PP
\fBTcl_GetObjResult\fR returns the result for \fIinterp\fR as a value.
The value's reference count is not incremented;
\fBTcl_GetObjResult\fR returns the result for \fIinterp\fR, without
incrementing its reference count.
if the caller needs to retain a long-term pointer to the value
they should use \fBTcl_IncrRefCount\fR to increment its reference count
in order to keep it from being freed too early or accidentally changed.
.PP
\fBTcl_SetResult\fR
\fBTcl_SetResult\fR sets \fIresult\fR as the result for \fIinterp\fR, replacing
arranges for \fIresult\fR to be the result for the current Tcl
command in \fIinterp\fR, replacing any existing result.
any existing result, and calls \fIfreeProc\fR to free \fIresult\fR.  See \fBTHE
The \fIfreeProc\fR argument specifies how to manage the storage
for the \fIresult\fR argument;
it is discussed in the section
\fBTHE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT\fR below.
If \fIresult\fR is \fBNULL\fR, then \fIfreeProc\fR is ignored
TCL_FREEPROC ARGUMENT TO TCL_SETRESULT\fR below.  If \fIresult\fR is
\fBNULL\fR, ignores \fIfreeProc\fR and sets the result for \fIinterp\fR to
and \fBTcl_SetResult\fR
re-initializes \fIinterp\fR's result to point to an empty string.
point to the empty string.
.PP
\fBTcl_GetStringResult\fR returns the result for \fIinterp\fR as a string.
\fBTcl_GetStringResult\fR returns the result for \fIinterp\fR as a string, i.e.
If the result was set to a value by a \fBTcl_SetObjResult\fR call,
the value form will be converted to a string and returned.
the bytes of the Tcl_Obj for the result, which can be decoded using
\fBTcl_UtfToExternal\fR.  This value is freed when its corresponding Tcl_Obj is
If the value's string representation contains null bytes,
this conversion will lose information.
For this reason, programmers are encouraged to
freed.Programmers are encouraged to use the newer Tcl_Obj API procedures, e.g.
write their code to use the new value API procedures
and to call \fBTcl_GetObjResult\fR instead.
to call \fBTcl_GetObjResult\fR instead.
.PP
\fBTcl_ResetResult\fR clears the result for \fIinterp\fR
\fBTcl_ResetResult\fR sets the empty string as the result for \fIinterp\fR and
and leaves the result in its normal empty initialized state.
If the result is a value,
its reference count is decremented and the result is left
pointing to an unshared value representing an empty string.
If the result is a dynamically allocated string, its memory is free*d
and the result is left as a empty string.
\fBTcl_ResetResult\fR also clears the error state managed by
clears the error state managed by \fBTcl_AddErrorInfo\fR,
\fBTcl_AddErrorInfo\fR, \fBTcl_AddObjErrorInfo\fR,
and \fBTcl_SetErrorCode\fR.
\fBTcl_AddObjErrorInfo\fR, and \fBTcl_SetErrorCode\fR.
.PP
\fBTcl_AppendResult\fR makes it easy to build up Tcl results in pieces.
\fBTcl_AppendResult\fR builds up a result from smaller pieces, appending each
It takes each of its \fIresult\fR arguments and appends them in order
to the current result associated with \fIinterp\fR.
\fIresult\fR in order to the current result for \fIinterp\fR.  It may be called
If the result is in its initialized empty state (e.g. a command procedure
was just invoked or \fBTcl_ResetResult\fR was just called),
then \fBTcl_AppendResult\fR sets the result to the concatenation of
its \fIresult\fR arguments.
\fBTcl_AppendResult\fR may be called repeatedly as additional pieces
of the result are produced.
repeatedly as additional pieces of the result are produced, and manages the
\fBTcl_AppendResult\fR takes care of all the
storage management issues associated with managing \fIinterp\fR's
result, such as allocating a larger result area if necessary.
It also manages conversion to and from the \fIresult\fR field of the
\fIinterp\fR so as to handle backward-compatibility with old-style
storage for the \fIinterp\fR's result, allocating a larger result area if
necessary.  It also manages conversion to and from the \fIresult\fR field of
the \fIinterp\fR to handle backward-compatibility with old-style extensions.
extensions.
Any number of \fIresult\fR arguments may be passed in a single
call; the last argument in the list must be (char *)NULL.
Any number of \fIresult\fR arguments may be passed in a single call; the last
argument in the list must be (char *)NULL.
.PP
\fBTcl_TransferResult\fR transfers interpreter state from \fIsourceInterp\fR
to \fItargetInterp\fR. The two interpreters must have been created in the
\fBTcl_TransferResult\fR transfers interpreter state from \fIsourceInterp\fR to
\fItargetInterp\fR, both of which must have been created in the same thread,
same thread.  If \fIsourceInterp\fR and \fItargetInterp\fR are the same,
nothing is done. Otherwise, \fBTcl_TransferResult\fR moves the result
from \fIsourceInterp\fR to \fItargetInterp\fR, and resets the result
in \fIsourceInterp\fR. It also moves the return options dictionary as
controlled by the return code value \fIcode\fR in the same manner
resets the result in \fIsourceInterp\fR, and moves the return options
dictionary as controlled by the return code value \fIcode\fR in the same manner
as \fBTcl_GetReturnOptions\fR.
.PP
If \fIsourceInterp\fR and \fItargetInterp\fR are the same, nothing is done.
.SH "DEPRECATED INTERFACES"
.SS "OLD STRING PROCEDURES"
.PP
Use of the following procedures is deprecated
since they manipulate the Tcl result as a string.
Procedures such as \fBTcl_SetObjResult\fR
The following procedures are deprecated since they manipulate the Tcl result as
a string.  Procedures such as \fBTcl_SetObjResult\fR can be significantly more
that manipulate the result as a value
can be significantly more efficient.
efficient.
.PP
\fBTcl_AppendElement\fR is similar to \fBTcl_AppendResult\fR in
\fBTcl_AppendElement\fR is like \fBTcl_AppendResult\fR, but it appends only one
that it allows results to be built up in pieces.
However, \fBTcl_AppendElement\fR takes only a single \fIelement\fR
argument and it appends that argument to the current result
as a proper Tcl list element.
\fBTcl_AppendElement\fR adds backslashes or braces if necessary
piece, and also appends that piece as a list item.
\fBTcl_AppendElement\fR adds backslashes or braces as necessary to ensure that
to ensure that \fIinterp\fR's result can be parsed as a list and that
\fIelement\fR will be extracted as a single element.
Under normal conditions, \fBTcl_AppendElement\fR will add a space
character to \fIinterp\fR's result just before adding the new
list element, so that the list elements in the result are properly
\fIelement\fR is properly formatted as a list item.  Under normal conditions,
\fBTcl_AppendElement\fR adds a space character to \fIinterp\fR's result just
before adding the new list element, so that the list elements in the result are
separated.
However if the new list element is the first in a list or sub-list
(i.e. \fIinterp\fR's current result is empty, or consists of the
single character
properly separated.  However if the new list element is the first item in the
list or sublist (i.e. \fIinterp\fR's current result is empty, or consists of
the single character
.QW { ,
or ends in the characters
.QW " {" )
then no space is added.
.SH "THE TCL_FREEPROC ARGUMENT TO TCL_SETRESULT"
.PP
\fBTcl_SetResult\fR's \fIfreeProc\fR argument specifies how
the Tcl system is to manage the storage for the \fIresult\fR argument.
If \fBTcl_SetResult\fR or \fBTcl_SetObjResult\fR are called
at a time when \fIinterp\fR holds a string result,
they do whatever is necessary to dispose of the old string result
(see the \fBTcl_Interp\fR manual entry for details on this).
.PP
If \fIfreeProc\fR is \fBTCL_STATIC\fR it means that \fIresult\fR
refers to an area of static storage that is guaranteed not to be
modified until at least the next call to \fBTcl_Eval\fR.
If \fIfreeProc\fR
\fIFreeProc\fR has the following type:
is \fBTCL_DYNAMIC\fR it means that \fIresult\fR was allocated with a call
to \fBTcl_Alloc\fR and is now the property of the Tcl system.
\fBTcl_SetResult\fR will arrange for the string's storage to be
released by calling \fBTcl_Free\fR when it is no longer needed.
If \fIfreeProc\fR is \fBTCL_VOLATILE\fR it means that \fIresult\fR
points to an area of memory that is likely to be overwritten when
\fBTcl_SetResult\fR returns (e.g. it points to something in a stack frame).
In this case \fBTcl_SetResult\fR will make a copy of the string in
dynamically allocated storage and arrange for the copy to be the
result for the current Tcl command.
.PP
If \fIfreeProc\fR is not one of the values \fBTCL_STATIC\fR,
\fBTCL_DYNAMIC\fR, and \fBTCL_VOLATILE\fR, then it is the address
of a procedure that Tcl should call to free the string.
This allows applications to use non-standard storage allocators.
When Tcl no longer needs the storage for the string, it will
call \fIfreeProc\fR. \fIFreeProc\fR should have arguments and
result that match the type \fBTcl_FreeProc\fR:
.PP
.CS
typedef void \fBTcl_FreeProc\fR(
        void *\fIblockPtr\fR);
.CE
.PP
When \fIfreeProc\fR is called, its \fIblockPtr\fR will be set to
the value of \fIresult\fR passed to \fBTcl_SetResult\fR.
When \fIfreeProc\fR is called, \fIblockPtr\fR is the \fIresult\fR value passed
to \fBTcl_SetResult\fR.

.SH "REFERENCE COUNT MANAGEMENT"
.PP
The interpreter result is one of the main places that owns references to
values, along with the bytecode execution stack, argument lists, variables,
and the list and dictionary collection values.
.PP
\fBTcl_SetObjResult\fR takes a value with an arbitrary reference count
\fI(specifically including zero)\fR and guarantees to increment the reference
count. If code wishes to continue using the value after setting it as the
result, it should add its own reference to it with \fBTcl_IncrRefCount\fR.
.PP
\fBTcl_GetObjResult\fR returns the current interpreter result value. This will
have a reference count of at least 1. If the caller wishes to keep the
interpreter result value, it should increment its reference count.
.PP
\fBTcl_GetStringResult\fR does not manipulate reference counts, but the string
it returns is owned by (and has a lifetime controlled by) the current
interpreter result value; it should be copied instead of being relied upon to
persist after the next Tcl API call, as most Tcl operations can modify the
interpreter result.
.PP
\fBTcl_SetResult\fR, \fBTcl_AppendResult\fR,
\fBTcl_AppendElement\fR, and \fBTcl_ResetResult\fR all modify the interpreter
result. They may cause the old interpreter result to have its reference count
decremented and a new interpreter result to be allocated. After they have been
called, the reference count of the interpreter result is guaranteed to be 1.
.SH "SEE ALSO"
Tcl_AddErrorInfo, Tcl_CreateObjCommand, Tcl_SetErrorCode, Tcl_Interp,
Tcl_GetReturnOptions
.SH KEYWORDS
append, command, element, list, value, result, return value, interpreter

'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\" Copyright (c) 2023 Nathan Coulter
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH Tcl n "8.6" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
.SH NAME
Tcl \- Tool Command Language
.SH SYNOPSIS
Summary of Tcl language syntax.
.BE
.SH DESCRIPTION
.PP
The following rules define the syntax and semantics of the Tcl language:
.
.IP "[1] \fBCommands.\fR"
A Tcl script is a string containing one or more commands.
Semi-colons and newlines are command separators unless quoted as
.IP "[1] \fBScript.\fR"
A script is composed of zero or more commands delimited by semi-colons or
newlines.
described below.
Close brackets are command terminators during command substitution
(see below) unless quoted.
.IP "[2] \fBEvaluation.\fR"
A command is evaluated in two steps.
.IP "[2] \fBCommand.\fR"
A command is composed of zero or more words delimited by whitespace.  The
First, the Tcl interpreter breaks the command into \fIwords\fR
and performs substitutions as described below.
These substitutions are performed in the same way for all
commands.
replacement for a substitution is included verbatim in the word. For example, a
space in the replacement is included in the word rather than becoming a
delimiter, and \fI\\\\\fR becomes a single backslash in the word.  Each word is
processed from left to right and each substitution is performed as soon as it
is complete.
Secondly, the first word is used to locate a routine to
carry out the command, and the remaining words of the command are
passed to that routine.
The routine is free to interpret each of its words
For example, the command
.RS
.PP
.CS
set y [set x 0][incr x][incr x]
in any way it likes, such as an integer, variable name, list,
or Tcl script.
Different commands interpret their words differently.
.IP "[3] \fBWords.\fR"
.CE
.PP
is composed of three words, and sets the value of \fIy\fR to \fI012\fR.
.PP
If hash
.PQ #
is the first character of what would otherwise be the first word of a command,
all characters up to the next newline are ignored.
.RE
.
.IP "[3] \fBBraced word.\fR"
Words of a command are separated by white space (except for
newlines, which are command separators).
.IP "[4] \fBDouble quotes.\fR"
If the first character of a word is double-quote
If a word is enclosed in braces
.PQ {
and
.PQ } ""
, the braces are removed and the enclosed characters become the word.  No
substitutions are performed.  Nested pairs of braces may occur within the word.
A brace preceded by an odd number of backslashes is not considered part of a
pair, and neither brace nor the backslashes are removed from the word.
.
.IP "[4] \fBQuoted word.\fR"
If a word is enclosed in double quotes
.PQ \N'34'
then the word is terminated by the next double-quote character.
, the double quotes are removed and the enclosed characters become the word.
If semi-colons, close brackets, or white space characters
(including newlines) appear between the quotes then they are treated
as ordinary characters and included in the word.
Command substitution, variable substitution, and backslash substitution
Substitutions are performed.
.
.IP "[5] \fBList.\fR"
A list has the form of a single command.  Newline is whitespace, and semicolon
has no special interpretation.  There is no script evaluation so there is no
argument expansion, variable substitution, or command substitution: Dollar-sign
are performed on the characters between the quotes as described below.
The double-quotes are not retained as part of the word.
.IP "[5] \fBArgument expansion.\fR"
If a word starts with the string
and open bracket have no special interpretation, and what would be argument
expansion in a script is invalid in a list.
.
.IP "[6] \fBArgument expansion.\fR"
If
.QW {*}
followed by a non-whitespace character, then the leading
.QW {*}
is removed and the rest of the word is parsed and substituted as any other
prefixes a word, it is removed.  After any remaining enclosing braces or quotes
word. After substitution, the word is parsed as a list (without command or
variable substitutions; backslash substitutions are performed as is normal for
a list and individual internal words may be surrounded by either braces or
double-quote characters), and its words are added to the command being
substituted. For instance,
.QW "cmd a {*}{b [c]} d {*}{$e f {g h}}"
are processed and applicable substitutions performed, the word, which must
be a list, is removed from the command, and in its place each word in the
list becomes an additional word in the command.  For example,
.CS
cmd a {*}{b [c]} d {*}{$e f {g h}}
.CE
is equivalent to
.CS
.QW "cmd a b {[c]} d {$e} f {g h}" .
cmd a b {[c]} d {$e} f {g h} .
.IP "[6] \fBBraces.\fR"
If the first character of a word is an open brace
.PQ {
and rule [5] does not apply, then
the word is terminated by the matching close brace
.CE
.
.IP "[7] \fBEvaluation.\fR"
To evaluate a script, an interpreter evaluates each successive command.  The
first word identifies a procedure, and the remaining words are passed to that
.PQ } "" .
Braces nest within the word: for each additional open
brace there must be an additional close brace (however,
if an open brace or close brace within the word is
procedure for further evaluation.  The procedure interprets each argument in
its own way, e.g. as an integer, variable name, list, mathematical expression,
script, or in some other arbitrary way.  The result of the last command is the
quoted with a backslash then it is not counted in locating the
matching close brace).
No substitutions are performed on the characters between the
braces except for backslash-newline substitutions described
below, nor do semi-colons, newlines, close brackets,
or white space receive any special interpretation.
The word will consist of exactly the characters between the
result of the script.
outer braces, not including the braces themselves.
.IP "[7] \fBCommand substitution.\fR"
If a word contains an open bracket
.
.IP "[8] \fBCommand substitution.\fR"
Each pair of brackets
.PQ [
then Tcl performs \fIcommand substitution\fR.
and
To do this it invokes the Tcl interpreter recursively to process
the characters following the open bracket as a Tcl script.
The script may contain any number of commands and must be terminated
by a close bracket
.PQ ] "" .
The result of the script (i.e. the result of its last command) is
.PQ ] ""
encloses a script and is replaced by the result of that script.
substituted into the word in place of the brackets and all of the
characters between them.
There may be any number of command substitutions in a single word.
Command substitution is not performed on words enclosed in braces.
.IP "[8] \fBVariable substitution.\fR"
If a word contains a dollar-sign
.IP "[9] \fBVariable substitution.\fR"
Each of the following forms begins with dollar sign
.PQ $
followed by one of the forms
described below, then Tcl performs \fIvariable
and is replaced by the value of the identified variable.  \fIname\fR names the
variable and is composed of ASCII letters (\fBA\fR\(en\fBZ\fR and
substitution\fR:  the dollar-sign and the following characters are
replaced in the word by the value of a variable.
\fBa\fR\(en\fBz\fR), digits (\fB0\fR\(en\fB9\fR), underscores, or namespace
delimiters (two or more colons).  \fIindex\fR is the name of an individual
variable within an array variable, and may be empty.
Variable substitution may take any of the following forms:
.RS
.TP 15
\fB$\fIname\fR
.
\fIName\fR is the name of a scalar variable;  the name is a sequence
\fIname\fR may not be empty.
of one or more characters that are a letter, digit, underscore,
or namespace separators (two or more colons).
Letters and digits are \fIonly\fR the standard ASCII ones (\fB0\fR\(en\fB9\fR,
\fBA\fR\(en\fBZ\fR and \fBa\fR\(en\fBz\fR).
.TP 15
\fB$\fIname\fB(\fIindex\fB)\fR
.
\fIName\fR gives the name of an array variable and \fIindex\fR gives
the name of an element within that array.
\fIName\fR must contain only letters, digits, underscores, and
namespace separators, and may be an empty string.
Letters and digits are \fIonly\fR the standard ASCII ones (\fB0\fR\(en\fB9\fR,
\fBA\fR\(en\fBZ\fR and \fBa\fR\(en\fBz\fR).
Command substitutions, variable substitutions, and backslash
substitutions are performed on the characters of \fIindex\fR.
\fIname\fR may be empty.  Substitutions are performed on \fIindex\fR.
.TP 15
\fB${\fIname\fB}\fR
.
\fIName\fR is the name of a scalar variable or array element.  It may contain
any characters whatsoever except for close braces.  It indicates an array
element if \fIname\fR is in the form
\fIname\fR may be empty.
.QW \fIarrayName\fB(\fIindex\fB)\fR
where \fIarrayName\fR does not contain any open parenthesis characters,
.QW \fB(\fR ,
.TP 15
or close brace characters,
.QW \fB}\fR ,
\fB${\fIname(index)\fB}\fR
and \fIindex\fR can be any sequence of characters except for close brace
characters.  No further
substitutions are performed during the parsing of \fIname\fR.
.
\fIname\fR may be empty. No substitutions are performed.
.PP
There may be any number of variable substitutions in a single word.
Variable substitution is not performed on words enclosed in braces.
.PP
Note that variables may contain character sequences other than those listed
above, but in that case other mechanisms must be used to access them (e.g.,
via the \fBset\fR command's single-argument form).
.RE
Variables that are not accessible through one of the forms above may be
accessed through other mechanisms, e.g. the \fBset\fR command.
.IP "[9] \fBBackslash substitution.\fR"
If a backslash
.IP "[10] \fBBackslash substitution.\fR"
Each backslash
.PQ \e
appears within a word then \fIbackslash substitution\fR occurs.
In all cases but those described below the backslash is dropped and
that is not part of one of the forms listed below is removed, and the next
the following character is treated as an ordinary
character and included in the word.
This allows characters such as double quotes, close brackets,
character is included in the word verbatim, which allows the inclusion of
characters that would normally be interpreted, namely whitespace, braces,
and dollar signs to be included in words without triggering
special processing.
The following table lists the backslash sequences that are
handled specially, along with the value that replaces each sequence.
brackets, double quote, dollar sign, and backslash.  The following sequences
are replaced as described:
.RS
.RS
.RS
.TP 7
\e\fBa\fR
.
Audible alert (bell) (Unicode U+000007).
Audible alert (bell) (U+7).
.TP 7
\e\fBb\fR
.
Backspace (Unicode U+000008).
Backspace (U+8).
.TP 7
\e\fBf\fR
.
Form feed (Unicode U+00000C).
Form feed (U+C).
.TP 7
\e\fBn\fR
.
Newline (Unicode U+00000A).
Newline (U+A).
.TP 7
\e\fBr\fR
.
Carriage-return (Unicode U+00000D).
Carriage-return (U+D).
.TP 7
\e\fBt\fR
.
Tab (Unicode U+000009).
Tab (U+9).
.TP 7
\e\fBv\fR
.
Vertical tab (Unicode U+00000B).
Vertical tab (U+B).
.TP 7
\e\fB<newline>\fIwhiteSpace\fR
.
A single space character replaces the backslash, newline, and all spaces
and tabs after the newline.  This backslash sequence is unique in that it
is replaced in a separate pre-pass before the command is actually parsed.
Newline preceded by an odd number of backslashes, along with the consecutive
spaces and tabs that immediately follow it, is replaced by a single space.
Because this happens before the command is split into words, it occurs even
This means that it will be replaced even when it occurs between braces,
and the resulting space will be treated as a word separator if it is not
in braces or quotes.
within braced words, and if the resulting space may subsequently be treated as
a word delimiter.
.TP 7
\e\e
.
Backslash
.PQ \e "" .
.TP 7
\e\fIooo\fR
.
The digits \fIooo\fR (one, two, or three of them) give a eight-bit octal
value for the Unicode character that will be inserted, in the range
\fI000\fR\(en\fI377\fR (i.e., the range U+000000\(enU+0000FF).
The parser will stop just before this range overflows, or when
Up to three octal digits form an eight-bit value for a Unicode character in the
range \fI0\fR\(en\fI377\fR, i.e. U+0\(enU+FF.  Only the digits that result in a
number in this range are consumed.
the maximum of three digits is reached.  The upper bits of the Unicode
character will be 0.
.TP 7
\e\fBx\fIhh\fR
.
The hexadecimal digits \fIhh\fR (one or two of them) give an eight-bit
Up to two hexadecimal digits form an eight-bit value for a Unicode character in
hexadecimal value for the Unicode character that will be inserted.  The upper
bits of the Unicode character will be 0 (i.e., the character will be in the
range U+000000\(enU+0000FF).
the range \fI0\fR\(en\fIFF\fR.
.TP 7
\e\fBu\fIhhhh\fR
.
The hexadecimal digits \fIhhhh\fR (one, two, three, or four of them) give a
Up to four hexadecimal digits form a 16-bit value for a Unicode character in
sixteen-bit hexadecimal value for the Unicode character that will be
inserted.  The upper bits of the Unicode character will be 0 (i.e., the
character will be in the range U+000000\(enU+00FFFF).
the range \fI0\fR\(en\fIFFFF\fR.
.TP 7
\e\fBU\fIhhhhhhhh\fR
.
The hexadecimal digits \fIhhhhhhhh\fR (one up to eight of them) give a
Up to eight hexadecimal digits form a 21-bit value for a Unicode character in
twenty-one-bit hexadecimal value for the Unicode character that will be
inserted, in the range U+000000\(enU+10FFFF.  The parser will stop just
before this range overflows, or when the maximum of eight digits
the range \fI0\fR\(en\fI10FFFF\fR.  Only the digits that result in a number in
this range are consumed.
is reached.  The upper bits of the Unicode character will be 0.
.RE
.RE
.PP
Backslash substitution is not performed on words enclosed in braces,
except for backslash-newline as described above.
.RE
.IP "[10] \fBComments.\fR"
If a hash character
.PQ #
appears at a point where Tcl is
expecting the first character of the first word of a command,
then the hash character and the characters that follow it, up
through the next newline, are treated as a comment and ignored.
The comment character only has significance when it appears
at the beginning of a command.
.IP "[11] \fBOrder of substitution.\fR"
Each character is processed exactly once by the Tcl interpreter
as part of creating the words of a command.
For example, if variable substitution occurs then no further
substitutions are performed on the value of the variable;  the
value is inserted into the word verbatim.
If command substitution occurs then the nested command is
processed entirely by the recursive call to the Tcl interpreter;
no substitutions are performed before making the recursive
call and no additional substitutions are performed on the result
of the nested script.
.RS
.PP
Substitutions take place from left to right, and each substitution is
evaluated completely before attempting to evaluate the next.  Thus, a
sequence like
.PP
.CS
set y [set x 0][incr x][incr x]
.CE
.PP
will always set the variable \fIy\fR to the value, \fI012\fR.
.RE
.IP "[12] \fBSubstitution and word boundaries.\fR"
Substitutions do not affect the word boundaries of a command,
except for argument expansion as specified in rule [5].
For example, during variable substitution the entire value of
the variable becomes part of a single word, even if the variable's
value contains spaces.
.
.SH KEYWORDS
backslash, command, comment, script, substitution, variable
'\" Local Variables:
'\" mode: nroff
'\" fill-column: 78
'\" End:

'\"
'\" Copyright (c) 2018 Donal K. Fellows
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH abstract n 0.3 TclOO "TclOO Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
oo::abstract \- a class that does not allow direct instances of itself

'\"
'\" Copyright (c) 1990-1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH after n 7.5 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
after \- Execute a command after a time delay

'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH append n "" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
append \- Append to variable

'\"
'\" Copyright (c) 1993-1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH array n 9.0 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
array \- Manipulate array variables

'\"
'\" Copyright (c) 1990-1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH bgerror n 7.5 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
bgerror \- Command invoked to process background errors

'\"
'\" Copyright (c) 1997 Sun Microsystems, Inc.
'\" Copyright (c) 2008 Donal K. Fellows
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH binary n 8.0 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
binary \- Insert and extract fields from binary strings
.SH SYNOPSIS

.PP
which returns a binary string equivalent to:
.PP
.CS
\fB\e254\fR
.CE
.PP
(i.e. \fB\exAC\fR) by
(i.e. \fB\exac\fR) by
truncating the high-bits of the character, and which is probably not
what is desired.
.RE
.IP \fBA\fR 5
This form is the same as \fBa\fR except that spaces are used for
padding instead of nulls.  For example,
.RS

.CS
\fBbinary format\fR B5B* 11100 111000011010
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\exE0\exE1\exA0\fR
\fB\exe0\exe1\exa0\fR
.CE
.RE
.IP \fBH\fR 5
Stores a string of \fIcount\fR hexadecimal digits in high-to-low
within each byte in the output binary string.  \fIArg\fR must contain a
sequence of characters in the set
.QW 0123456789abcdefABCDEF .

.CS
\fBbinary format\fR H3H*H2 ab DEF 987
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\exAB\ex00\exDE\exF0\ex98\fR
\fB\exab\ex00\exde\exf0\ex98\fR
.CE
.RE
.IP \fBh\fR 5
This form is the same as \fBH\fR except that the digits are stored in
low-to-high order within each byte. This is seldom required. For example,
.RS
.PP
.CS
\fBbinary format\fR h3h*h2 AB def 987
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\exBA\ex00\exED\ex0F\ex89\fR
\fB\exba\ex00\exed\ex0f\ex89\fR
.CE
.RE
.IP \fBc\fR 5
Stores one or more 8-bit integer values in the output string.  If no
\fIcount\fR is specified, then \fIarg\fR must consist of an integer
value. If \fIcount\fR is specified, \fIarg\fR must consist of a list
containing at least that many integers. The low-order 8 bits of each integer

.CS
\fBbinary format\fR c3cc* {3 -3 128 1} 260 {2 5}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\ex03\exFD\ex80\ex04\ex02\ex05\fR
\fB\ex03\exfd\ex80\ex04\ex02\ex05\fR
.CE
.PP
whereas:
.PP
.CS
\fBbinary format\fR c {2 5}
.CE

.CS
\fBbinary format\fR s3 {3 -3 258 1}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\ex03\ex00\exFD\exFF\ex02\ex01\fR
\fB\ex03\ex00\exfd\exff\ex02\ex01\fR
.CE
.RE
.IP \fBS\fR 5
This form is the same as \fBs\fR except that it stores one or more
16-bit integers in big-endian byte order in the output string.  For
example,
.RS
.PP
.CS
\fBbinary format\fR S3 {3 -3 258 1}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\ex00\ex03\exFF\exFD\ex01\ex02\fR
\fB\ex00\ex03\exff\exfd\ex01\ex02\fR
.CE
.RE
.IP \fBt\fR 5
This form (mnemonically \fItiny\fR) is the same as \fBs\fR and \fBS\fR
except that it stores the 16-bit integers in the output string in the
native byte order of the machine where the Tcl script is running.
To determine what the native byte order of the machine is, refer to

.CS
\fBbinary format\fR i3 {3 -3 65536 1}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\ex03\ex00\ex00\ex00\exFD\exFF\exFF\exFF\ex00\ex00\ex01\ex00\fR
\fB\ex03\ex00\ex00\ex00\exfd\exff\exff\exff\ex00\ex00\ex01\ex00\fR
.CE
.RE
.IP \fBI\fR 5
This form is the same as \fBi\fR except that it stores one or more one
or more 32-bit integers in big-endian byte order in the output string.
For example,
.RS
.PP
.CS
\fBbinary format\fR I3 {3 -3 65536 1}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\ex00\ex00\ex00\ex03\exFF\exFF\exFF\exFD\ex00\ex01\ex00\ex00\fR
\fB\ex00\ex00\ex00\ex03\exff\exff\exff\exfd\ex00\ex01\ex00\ex00\fR
.CE
.RE
.IP \fBn\fR 5
This form (mnemonically \fInumber\fR or \fInormal\fR) is the same as
\fBi\fR and \fBI\fR except that it stores the 32-bit integers in the
output string in the native byte order of the machine where the Tcl
script is running.

.CS
\fBbinary format\fR f2 {1.6 3.4}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\exCD\exCC\exCC\ex3F\ex9A\ex99\ex59\ex40\fR
\fB\excd\excc\excc\ex3f\ex9a\ex99\ex59\ex40\fR
.CE
.RE
.IP \fBr\fR 5
This form (mnemonically \fIreal\fR) is the same as \fBf\fR except that
it stores the single-precision floating point numbers in little-endian
order.  This conversion only produces meaningful output when used on
machines which use the IEEE floating point representation (very

.CS
\fBbinary format\fR d1 {1.6}
.CE
.PP
will return a binary string equivalent to:
.PP
.CS
\fB\ex9A\ex99\ex99\ex99\ex99\ex99\exF9\ex3F\fR
\fB\ex9a\ex99\ex99\ex99\ex99\ex99\exf9\ex3f\fR
.CE
.RE
.IP \fBq\fR 5
This form (mnemonically the mirror of \fBd\fR) is the same as \fBd\fR
except that it stores the double-precision floating point numbers in
little-endian order.  This conversion only produces meaningful output
when used on machines which use the IEEE floating point representation

.QW \fB*\fR ,
then all of the remaining hex digits in \fIstring\fR will be
scanned. If \fIcount\fR is omitted, then one hex digit will be
scanned. For example,
.RS
.PP
.CS
\fBbinary scan\fR \ex07\exC6\ex05\ex1F\ex34 H3H* var1 var2
\fBbinary scan\fR \ex07\exC6\ex05\ex1f\ex34 H3H* var1 var2
.CE
.PP
will return \fB2\fR with \fB07c\fR stored in \fIvar1\fR and
\fB051f34\fR stored in \fIvar2\fR.
.RE
.IP \fBh\fR 5
This form is the same as \fBH\fR, except the digits are taken in

.QW \fB*\fR ,
then all of the remaining bytes in \fIstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 16-bit integer will be scanned.  For
example,
.RS
.PP
.CS
\fBbinary scan\fR \ex05\ex00\ex07\ex00\exF0\exFF s2s* var1 var2
\fBbinary scan\fR \ex05\ex00\ex07\ex00\exf0\exff s2s* var1 var2
.CE
.PP
will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR
stored in \fIvar2\fR.  Note that the integers returned are signed unless
\fBsu\fR is used in place of \fBs\fR.
.RE
.IP \fBS\fR 5
This form is the same as \fBs\fR except that the data is interpreted
as \fIcount\fR 16-bit integers represented in big-endian byte
order.  For example,
.RS
.PP
.CS
\fBbinary scan\fR \ex00\ex05\ex00\ex07\exFF\exF0 S2S* var1 var2
\fBbinary scan\fR \ex00\ex05\ex00\ex07\exff\exf0 S2S* var1 var2
.CE
.PP
will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR
stored in \fIvar2\fR.
.RE
.IP \fBt\fR 5
The data is interpreted as \fIcount\fR 16-bit signed integers

.QW \fB*\fR ,
then all of the remaining bytes in \fIstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 32-bit integer will be scanned.  For
example,
.RS
.PP
.CS
set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exF0\exFF\exFF\exFF
set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exf0\exff\exff\exff
\fBbinary scan\fR $str i2i* var1 var2
.CE
.PP
will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR
stored in \fIvar2\fR.  Note that the integers returned are signed unless
\fBiu\fR is used in place of \fBi\fR.
.RE
.IP \fBI\fR 5
This form is the same as \fBI\fR except that the data is interpreted
as \fIcount\fR 32-bit signed integers represented in big-endian byte
order, or as unsigned if \fBu\fR is placed
immediately after the \fBI\fR.  For example,
.RS
.PP
.CS
set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exFF\exFF\exFF\exF0
set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exff\exff\exff\exf0
\fBbinary scan\fR $str I2I* var1 var2
.CE
.PP
will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR
stored in \fIvar2\fR.
.RE
.IP \fBn\fR 5

.QW \fB*\fR ,
then all of the remaining bytes in \fIstring\fR will be scanned.  If
\fIcount\fR is omitted, then one 64-bit integer will be scanned.  For
example,
.RS
.PP
.CS
set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exF0\exFF\exFF\exFF
set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exf0\exff\exff\exff
\fBbinary scan\fR $str wi* var1 var2
.CE
.PP
will return \fB2\fR with \fB30064771077\fR stored in \fIvar1\fR and
\fB\-16\fR stored in \fIvar2\fR.
.RE
.IP \fBW\fR 5
This form is the same as \fBw\fR except that the data is interpreted
as \fIcount\fR 64-bit signed integers represented in big-endian byte
order, or as unsigned if \fBu\fR is placed
immediately after the \fBW\fR.  For example,
.RS
.PP
.CS
set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exFF\exFF\exFF\exF0
set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exff\exff\exff\exf0
\fBbinary scan\fR $str WI* var1 var2
.CE
.PP
will return \fB2\fR with \fB21474836487\fR stored in \fIvar1\fR and \fB\-16\fR
stored in \fIvar2\fR.
.RE
.IP \fBm\fR 5

bytes that are scanned may vary.  If the data does not represent a
valid floating point number, the resulting value is undefined and
compiler dependent.  For example, on a Windows system running on an
Intel Pentium processor,
.RS
.PP
.CS
\fBbinary scan\fR \ex3F\exCC\exCC\exCD f var1
\fBbinary scan\fR \ex3f\excc\excc\excd f var1
.CE
.PP
will return \fB1\fR with \fB1.6000000238418579\fR stored in
\fIvar1\fR.
.RE
.IP \fBr\fR 5
This form is the same as \fBf\fR except that the data is interpreted

This form is the same as \fBf\fR except that the data is interpreted
as \fIcount\fR double-precision floating point numbers in the
machine's native representation. For example, on a Windows system
running on an Intel Pentium processor,
.RS
.PP
.CS
\fBbinary scan\fR \ex9A\ex99\ex99\ex99\ex99\ex99\exF9\ex3F d var1
\fBbinary scan\fR \ex9a\ex99\ex99\ex99\ex99\ex99\exf9\ex3f d var1
.CE
.PP
will return \fB1\fR with \fB1.6000000000000001\fR
stored in \fIvar1\fR.
.RE
.IP \fBq\fR 5
This form is the same as \fBd\fR except that the data is interpreted

'\"
'\" Copyright (c) 1993-1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH break n "" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
break \- Abort looping command

'\"
'\" Copyright (c) 2018 Donal K. Fellows
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH callback n 0.3 TclOO "TclOO Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
callback, mymethod \- generate callbacks to methods

'\"
'\" Copyright (c) 1993-1994 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\" Contributions from Don Porter, NIST, 2003.  (not subject to US copyright)
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH catch n "8.5" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
catch \- Evaluate script and trap exceptional returns

'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
'\"
.TH cd n "" Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
cd \- Change working directory

'\"
'\" Copyright (c) 2005-2006 Donal K. Fellows
'\" Copyright (c) 2021 Nathan Coulter
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" Copyright (c) 2024 Nathan Coulter
'\"
'\" You may distribute and/or modify this program under the terms of the GNU
'\" Affero General Public License as published by the Free Software Foundation,
'\" either version 3 of the License, or (at your option) any later version.
'\"
'\" See the file "COPYING" for information on usage and redistribution.
.TH chan n 8.5 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
chan \- Read, write and manipulate channels
chan \- Reads, writes and manipulates channels.
.SH SYNOPSIS
\fBchan \fIoption\fR ?\fIarg arg ...\fR?
\fBchan \fIprocedure\fR ?\fIarg arg ...\fR?
.BE
.SH DESCRIPTION
.PP
This command provides several operations for reading from, writing to
and otherwise manipulating open channels (such as have been created
\fBchan\fR provides procedures for reading from, writing to, and
otherwise manipulating channels like those created by \fBopen\fR and
with the \fBopen\fR and \fBsocket\fR commands, or the default named
channels \fBstdin\fR, \fBstdout\fR or \fBstderr\fR which correspond to
the process's standard input, output and error streams respectively).
\fIOption\fR indicates what to do with the channel; any unique
abbreviation for \fIoption\fR is acceptable. Valid options are:
\fBsocket\fR, or the default channels \fBstdin\fR, \fBstdout\fR or \fBstderr\fR
which correspond respectively to the standard input, output, and error streams
of the process.
Available procedures are:
.\" METHOD: blocked
.TP
\fBchan blocked \fIchannel\fR
.
This tests whether the last input operation on the channel called
\fIchannel\fR failed because it would have otherwise caused the
process to block, and returns 1 if that was the case. It returns 0
Returns 1 when \fIchannel\fR is non-blocking and the last input operation on
\fIchannel\fR failed because it would have otherwise caused the process to
block, and 0 otherwise.
otherwise. Note that this only ever returns 1 when the channel has
been configured to be non-blocking; all Tcl channels have blocking
turned on by default.
.\" METHOD: close
.TP
\fBchan close \fIchannel\fR ?\fIdirection\fR?
.
Close and destroy the channel called \fIchannel\fR. Note that this
deletes all existing file-events registered on the channel.
Closes \fIchannel\fR, deleting any existing event handlers established for it,
and returns the empty string.  Once both sides of a \fIchannel\fR are closed,
If the \fIdirection\fR argument (which must be \fBread\fR or \fBwrite\fR or
any unique abbreviation of them) is present, the channel will only be
half-closed, so that it can go from being read-write to write-only or
read-only respectively. If a read-only channel is closed for reading, it is
the same as if the channel is fully closed, and respectively similar for
write-only channels. Without the \fIdirection\fR argument, the channel is
closed for both reading and writing (but only if those directions are
currently open). It is an error to close a read-only channel for writing, or a
write-only channel for reading.
\fIchannel\fR no-longer exists in the current \fBinterp\fR.
.RS
.PP
As part of closing the channel, all buffered output is flushed to the
channel's output device (only if the channel is ceasing to be writable), any
If \fIdirection\fR, which may be \fBread\fR or \fBwrite\fR or any unique
abbreviation of those words, is given, closes only that side of \fIchannel\fR.
buffered input is discarded (only if the channel is ceasing to be readable),
the underlying operating system resource is closed and \fIchannel\fR becomes
unavailable for future use (both only if the channel is being completely
closed).
If \fIchannel\fR is read-write and the write side is closed, it becomes
read-only, or if the read side is closed, it becomes write-only.
.PP
.PP
Discards any buffered input before closing the read side of \fIchannel\fR.
If the channel is blocking and the channel is ceasing to be writable, the
Fully flushes any output before closing the write side of \fIchannel\fR unless
command does not return until all output is flushed.  If the channel is
non-blocking and there is unflushed output, the channel remains open and the
command returns immediately; output will be flushed in the background and the
channel will be closed when all the flushing is complete.
it is non-blocking mode, where it makes \fIchannel\fR unavailable, returns
immediately, and flushes any buffered output the background before actually
closing \fIchannel\fR.
.PP
If \fIchannel\fR is a blocking channel for a command pipeline then
\fBchan close\fR waits for the child processes to complete.
Returns an error if \fIchannel\fR is blocking and error occurs while flushing
output.  Produces an error in the same manner as \fBexec\fR if a
process in a command pipeline created by \fBopen\fR returns an error (either by
returning a non-zero exit code or writing to its standard error file
descriptor).
.PP
If the channel is shared between interpreters, then \fBchan close\fR
makes \fIchannel\fR unavailable in the invoking interpreter but has
If \fIchannel\fR is a command pipeline and is in blocking mode, waits
no other effect until all of the sharing interpreters have closed the
channel. When the last interpreter in which the channel is registered
for the connected processes to complete before closing \fIchannel\fR.
invokes \fBchan close\fR (or \fBclose\fR), the cleanup actions
described above occur. With half-closing, the half-close of the channel only
applies to the current interpreter's view of the channel until all channels
have closed it in that direction (or completely).
See the \fBinterp\fR command for a description of channel sharing.
.PP
Channels are automatically fully closed when an interpreter is destroyed and
when the process exits.  Channels are switched to blocking mode, to
Only affects the current interpreter.  If \fIchannel\fR is open in any other
interpreter, its state is unchanged there.  See \fBinterp\fR for a description
of channel sharing.
ensure that all output is correctly flushed before the process exits.
.PP
The command returns an empty string, and may generate an error if
an error occurs while flushing output.  If a command in a command
pipeline created with \fBopen\fR returns an error, \fBchan close\fR
Closing one side of a socket or command pipeline may cause the underlying
generates an error (similar to the \fBexec\fR command.)
system resource to be closed or destroyed, along with whatever side-effects
that entails for the process on the other side of the pipeline.
.PP
Note that half-closes of sockets and command pipelines can have important side
effects because they result in a shutdown() or close() of the underlying
system resource, which can change how other processes or systems respond to
the Tcl program.
When the last interpreter sharing a channel is destroyed, the channel is
switched to blocking mode, fully flushed, and then closed.
.PP
Channels are automatically closed when an interpreter is destroyed and
when the process exits.
also when the process exits.
From 8.6 on (TIP#398), nonblocking channels are no longer switched to
blocking mode when exiting; this guarantees a timely exit even when the
peer or a communication channel is stalled. To ensure proper flushing of
stalled nonblocking channels on exit, one must now either (a) actively
switch them back to blocking or (b) use the environment variable
\fBTCL_FLUSH_NONBLOCKING_ON_EXIT\fR, which when set and not equal to
.QW \fB0\fR
restores the previous behavior.
.RE
.\" METHOD: configure
.TP
\fBchan configure \fIchannel\fR ?\fIoptionName\fR? ?\fIvalue\fR? ?\fIoptionName value\fR?...
\fBchan configure \fIchannel\fR ?\fIoption\fR? ?\fIvalue\fR? ?\fIoption value\fR?...
.
Query or set the configuration options of the channel named
\fIchannel\fR.
Sets or gets the configuration of \fIchannel\fR.
.RS
.PP
If no \fIoptionName\fR or \fIvalue\fR arguments are supplied, the
command returns a list containing alternating option names and values
for the channel.  If \fIoptionName\fR is supplied but no \fIvalue\fR
then the command returns the current value of the given option.  If
If no \fIoption\fR or \fIvalue\fR arguments are given, \fBchan configure\fR
returns a dictionary of option names and values for \fIchannel\fR.  If
\fIoption\fR is supplied without a \fIvalue\fR, \fBchan configure\fR returns
the current value that option.  If one or more values are given, \fBchan
one or more pairs of \fIoptionName\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.
configure\fR sets each of the given options to the corresponding \fIvalue\fR
and returns the 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 following options are supported for all channels. Each type of
channel may provide additional options. Those options are described in the
the manual entry for the command that creates each type of channel
for the options supported by that specific type of channel. For
example, see the manual entry for the \fBsocket\fR command for additional
relevant documentation. For example, additional options are documented for
options for sockets, and the \fBopen\fR command for additional options for
serial devices.
\fBsocket\fR, and also for serial devices at \fBopen\fR.
.RE
.\" OPTION: -blocking
.TP
\fB\-blocking\fI boolean\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
If \fB\-blocking\fR is set to \fBtrue\fR (default), reading from or writing to
\fIchannel\fR may cause the process to block indefinitely.  Otherwise,
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 \fBchan gets\fR, \fBchan read\fR, \fBchan
puts\fR, \fBchan flush\fR, and \fBchan close\fR commands; see the
operations such as \fBchan gets\fR, \fBchan read\fR, \fBchan puts\fR, \fBchan
flush\fR, and \fBchan close\fR take care not to block.  For non-blocking mode
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 \fBTcl_DoOneEvent\fR or invoking the \fBvwait\fR
to work correctly the event loop must be active, e.g. via 
\fBTcl_DoOneEvent\fR or \fBvwait\fR or by using Tk, so that channel events
command).
are processed.
.\" OPTION: -buffering
.TP
\fB\-buffering\fI newValue\fR
.
If \fInewValue\fR is \fBfull\fR then the I/O system will buffer output
until its internal buffer is full or until the \fBchan flush\fR
command is invoked. If \fInewValue\fR is \fBline\fR, then the I/O
If \fInewValue\fR is \fBfull\fR, which is the default, output is buffered
until the internal buffer is full or until \fBchan flush\fR is called. If
\fInewValue\fR is \fBline\fR, output is flushed each time a end-of-line
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
character is written. If \fInewValue\fR is \fBnone\fR, output is flushed after
every output operation.  For \fBstdin\fR, \fBstdout\fR, and channels that
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
connect to terminal-like devices, the default value is \fBline\fR.  For
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.
\fBstderr\fR the default value is \fBnone\fR.
.\" OPTION: -buffersize
.TP
\fB\-buffersize\fI newSize\fR
.
\fInewSize\fR must be an integer; its value is used to set the size
of buffers, in bytes, subsequently allocated for this channel to store
\fInewSize\fR, an integer no greater than one million, is the size in bytes of
any input or output buffers subsequently allocated for \fIchannel\fR.
input or output. \fInewSize\fR must be a number of no more than one
million, allowing buffers of up to one million bytes in size.
.\" OPTION: -encoding
.TP
\fB\-encoding\fR \fIname\fR
\fB\-encoding\fR \fIencoding\fR
.
This option is used to specify the encoding of the channel as one of
the named encodings returned by \fBencoding names\fR, so that the
data can be converted to and from
Sets the encoding of \fIchannel\fR to \fIencoding\fR which should be one of the
encodings returned by \fBencoding names\fR.
Input is converted from the encoding into Unicode, and output is converted
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.
from Unicode to the encoding.
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 \fBiso8859-1\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.  It is usually better to set the
\fB\-translation\fR option to \fBbinary\fR when you want to transfer
binary data, as this turns off the other automatic interpretations of
the bytes in the stream as well.
.PP
The default encoding for newly opened channels is the same platform-
and locale-dependent system encoding used for interfacing with the
operating system, as returned by \fBencoding system\fR.
The encoding of a new channel is the value of \fBencoding system\fR,
which returns the platform- and locale-dependent system encoding used to
interface with the operating system,
.RE
.\" OPTION: -eofchar
.TP
\fB\-eofchar\fI char\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.
Otherwise (the default) there is no special end of file character marker.
The acceptable range for \fB\-eofchar\fR values is \ex01 - \ex7f;
attempting to set \fB\-eofchar\fR to a value outside of this range will
generate an error.
\fIchar\fR signals the end of the data when it is encountered in the input.
If \fIchar\fR is the empty string, there is no special character that marks
the end of the data.
.RS
.PP
The default value is the empty string.  The acceptable range is \ex01 -
\ex7f.  A value outside this range results in an error.
.RE
.VS "TCL8.7 TIP656"
.\" OPTION: -profile
.TP
\fB\-profile\fI profile\fR
.
Specifies the encoding profile to be used on the channel. The encoding
transforms in use for the channel's input and output will then be subject to the
rules of that profile. Any failures will result in a channel error. See
\fBPROFILES\fR in the \fBencoding(n)\fR documentation for details about encoding
profiles.
Indicates the encoding profile to be used on \fIchannel\fR. The encoding
transforms in use for the input and output of \fIchannel\fR will then be
subject to the rules of that profile. Any failures will result in a channel
error. See \fBPROFILES\fR in the \fBencoding(n)\fR documentation for details
about encoding profiles.
.VE "TCL8.7 TIP656"
.\" OPTION: -translation
.TP
\fB\-translation\fI translation\fR
.TP
\fB\-translation\fR \fB{\fIinTranslation outTranslation\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 \fBchan gets\fR and \fBchan read\fR) the Tcl I/O system
In Tcl a single line\-feed character (\fBlf\fR) represents the end of a
line.  However, the end of a line of a may be represented differently on
different platforms, or even for different devices on the same platform.  For
example, in UNIX \fBlf\fR is normally used in files, and a carriage-return
character followed by a line-feed character (\fBcrlf\fR) is
normally used in network connections.  Therefore, when decoding, e.g. with
\fBchan gets\fR and \fBchan read\fR, each particular end-of-line representation
automatically translates the external end-of-line representation into
newline characters.  Upon output (i.e., with \fBchan puts\fR), the I/O
system translates newlines to the external end-of-line representation.
The default translation mode, \fBauto\fR, handles all the common cases
automatically, but the \fB\-translation\fR option provides explicit
control over the end of line translations.
is translated into \fBlf\fR for Tcl.  Before encoding, e.g. with \fBchan
puts\fR, each \fBlf\fR is translated to the approprate end\-of\-line
representation for the target.  The default translation setting is \fBauto\fR,
which handles all the common cases.  When needed, \fB\-translation\fR provides
explicit control over the end\-of\-line representation.
.RS
.PP
The value associated with \fB\-translation\fR is a single item for
Returns the input translation if \fIchannel\fR is read\-only, the output
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
translation if \fIchannel\fR is write\-only, and both the input translation and
the output translation if \fIchannel\fR is read\-write.  When two
translations are given, they indicate the input and output translation
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
respectively.  When only one translation is given for a read\-write channel, it
is the translation for both input and output.  The following values are
currently supported:
.IP \fBauto\fR
As the input translation mode, \fBauto\fR treats any of newline
(\fBlf\fR), carriage return (\fBcr\fR), or carriage return followed by
The default.  For input each occurrence of \fBlf\fR, carriage-return character
(\fBcr\fR), or \fBcrlf\fR is translated into \fBlf\fR for Tcl.  For output,
a newline (\fBcrlf\fR) 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,
each \fBlf\fR is translated into a the appropriate representation for the
\fBauto\fR chooses a platform specific representation; for sockets on
all platforms Tcl chooses \fBcrlf\fR, for all Unix flavors, it chooses
\fBlf\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.
target:  For all Unix variants it is \fBlf\fR, and for all Windows variants it
is \fBcrlf\fR, except that for sockets on all platforms it is \fBcrlf\fR for
both input and output.
.IP \fBbinary\fR
Like \fBlf\fR, no end-of-line translation is performed, but in addition, sets
\fB\-eofchar\fR to the empty string to disable it, and sets \fB\-encoding\fR
to \fBiso8859-1\fR.  With this one setting, a channel is fully configured
for binary input and output:  Each byte read from the channel
becomes the Unicode character having the same value as that byte, and each
character written to the channel becomes a single byte in the output.  This
makes it possible to work seamlessly with binary data as long as each character
in the data remains in the range of 0 to 255 so that there is no distinction
between binary data and text.  For example, A JPEG image can be read from a
such a channel, manipulated, and then written back to such a channel.
Like \fBlf\fR, prevents end-of-line translation, but also sets \fB\-eofchar\fR
to the empty string to disable it, and sets \fB\-encoding\fR to
\fBiso8859-1\fR.  This one argument fully configures \fIchannel\fR for bytewise
input and output:  Each byte is read from \fIchannel\fR as the Unicode
character having the same value as that byte, and each character written to
\fIchannel\fR is encoded a single byte having the value of the character.  This
makes it possible to treat text as byte values as long as each character in
remains in the range of 0 to 255 so that the correspondance between a character
and a byte is maintained.  For example, A JPEG image can be read from
\fIchannel\fR, manipulated, and then written back to \fIchannel\fR.
.IP \fBcr\fR
The end of a line in the underlying file or device is represented by a
The end of a line is encoded as \fBcr\fR.  For input, each \fBcr\fR is
single carriage return character.  As the input translation mode,
\fBcr\fR mode converts carriage returns to newline characters.  As the
output translation mode, \fBcr\fR mode translates newline characters
translated to \fBlf\fR, and for output each \fBlf\fR is translated to \fBcr\fR.
to carriage returns.
.IP \fBcrlf\fR
The end of a line in the underlying file or device is represented by a
The end of a line is encoded as a \fBcrlf\fR.  For input, each \fBcrlf\fR is
carriage return character followed by a linefeed character.  As the
input translation mode, \fBcrlf\fR mode converts
translated to \fBlf\fR.  For output, each \fBlf\fR is translated to \fBcrlf\fR.
carriage-return-linefeed sequences to newline characters.  As the
output translation mode, \fBcrlf\fR mode translates newline characters
to carriage-return-linefeed sequences.  This mode is typically used on
Windows platforms and for network connections.
This translation is typically used for network connections, and is also used on
Windows systems.
.IP \fBlf\fR
The end of a line in the underlying file or device is represented by a
The end of a line is encoded as \fBlf\fR so no translations occur during either
single newline (linefeed) character.  In this mode no translations
occur during either input or output.  This mode is typically used on
UNIX platforms.
input or output.  This translation is typically used on UNIX platforms,
.RE
.RE
.\" METHOD: copy
.TP
\fBchan copy \fIinputChan outputChan\fR ?\fB\-size \fIsize\fR? ?\fB\-command \fIcallback\fR?
.
Reads characters from \fIinputChan\fR and writes them to \fIoutputChan\fR until
all characters are copied, blocking until the copy is complete and returning

.QW "channel busy"
error.
.RE
.\" METHOD: create
.TP
\fBchan create \fImode cmdPrefix\fR
.
This subcommand creates a new script level channel using the command
Creates a new channel, called a \fBreflected\fR channel, with \fIcmdPrefix\fR
prefix \fIcmdPrefix\fR as its handler. Any such channel is called a
\fBreflected\fR channel. The specified command prefix, \fBcmdPrefix\fR,
as its handler, and returns the name of the channel.  \fBcmdPrefix\fR is the
must be a non-empty list, and should provide the API described in the
\fBrefchan\fR manual page. The handle of the new channel is
first words of a command that provides the interface for a \fBrefchan\fR.
returned as the result of the \fBchan create\fR command, and the
channel is open. Use either \fBclose\fR or \fBchan close\fR to remove
the channel.
.RS
.PP
The argument \fImode\fR specifies if the new channel is opened for
reading, writing, or both. It has to be a list containing any of the
strings
\fBImode\fR is a list of one or more of the strings
.QW \fBread\fR
or
.QW \fBwrite\fR ,
The list must have at least one
indicating whether the channel is a read channel, a write channel, or both.
element, as a channel you can neither write to nor read from makes no
sense. The handler command for the new channel must support the chosen
It is an error if the handler does not support the chosen mode.
mode, or an error is thrown.
.PP
The command prefix is executed in the global namespace, at the top of
The handler is called as needed from the global namespace at the top level, and
call stack, following the appending of arguments as described in the
\fBrefchan\fR manual page. Command resolution happens at the
command resolution happens there at the time of the call.  If the handler is
time of the call. Renaming the command, or destroying it means that
the next call of a handler method may fail, causing the channel
command invoking the handler to fail as well. Depending on the
subcommand being invoked, the error message may not be able to explain
renamed or deleted any subsequent attempt to call it is an error, which may
not be able to describe the failure.
the reason for that failure.
.PP
Every channel created with this subcommand knows which interpreter it
was created in, and only ever executes its handler command in that
interpreter, even if the channel was shared with and/or was moved into
The handler is always called in the interpreter and thread it was created in,
even if the channel was shared with or moved into a different interpreter in a
a different interpreter. Each reflected channel also knows the thread
it was created in, and executes its handler command only in that
thread, even if the channel was moved into a different thread. To this
different thread.  This is achieved through event dispatch, so if the event
end all invocations of the handler are forwarded to the original
thread by posting special events to it. This means that the original
thread (i.e. the thread that executed the \fBchan create\fR command)
must have an active event loop, i.e. it must be able to process such
events. Otherwise the thread sending them will \fIblock
indefinitely\fR. Deadlock may occur.
loop is not entered, e.g. by calling \fBTcl_DoOneEvent\fR or \fBvwait\fR or
using Tk, the thread performing the channel operation \fIblocks
indefinitely\fR, resulting in deadlock.
.PP
Note that this permits the creation of a channel whose two endpoints
live in two different threads, providing a stream-oriented bridge
One side of a channel may be in one thread while the other side is in a
different thread, providing a stream-oriented bridge between the threads. This
between these threads. In other words, we can provide a way for
regular stream communication between threads instead of having to send
commands.
provides a method for regular stream communication between threads as an
alternative to sending commands.
.PP
When a thread or interpreter is deleted, all channels created with
When the interpreter the handler is in is deleted each channel associated with
this subcommand and using this thread/interpreter as their computing
base are deleted as well, in all interpreters they have been shared
the handler is deleted as well, regardless of which interpreter or thread it
with or moved into, and in whatever thread they have been transferred
to. While this pulls the rug out under the other thread(s) and/or
interpreter(s), this cannot be avoided. Trying to use such a channel
will cause the generation of a regular error about unknown channel
handles.
is currently in or shared with.
.PP
This subcommand is \fBsafe\fR and made accessible to safe
\fBchan create\fR is \fBsafe\fR and is accessible to safe interpreters.  The
interpreters.  While it arranges for the execution of arbitrary Tcl
code the system also makes sure that the code is always executed
within the safe interpreter.
handler is always called in the safe interpreter it was created in.
.RE
.\" METHOD: eof
.TP
\fBchan eof \fIchannel\fR
.
Test whether the last input operation on the channel called
\fIchannel\fR failed because the end of the data stream was reached,
returning 1 if end-of-file was reached, and 0 otherwise.
Returns 1 if the last read on \fIchannel\fR failed because the end of the data
was already reached, and 0 otherwise.
.\" METHOD: event
.TP
\fBchan event \fIchannel event\fR ?\fIscript\fR?
.
Arrange for the Tcl script \fIscript\fR to be installed as a \fIfile
event handler\fR to be called whenever the channel called
\fIchannel\fR enters the state described by \fIevent\fR (which must
be either \fBreadable\fR or \fBwritable\fR); only one such handler may
Arranges for the given script, called a \fBchannel event handler\fR, to be
called whenever the given event, either
.QW \fBreadable\fR
or
.QW \fBwritable\fR
be installed per event per channel at a time.  If \fIscript\fR is the
empty string, the current handler is deleted (this also happens if the
channel is closed or the interpreter deleted).  If \fIscript\fR is
occurs on \fIchannel\fR, replacing any script that was previously set.  If
\fIscript\fR is the empty string the current handler is deleted.  If
\fIscript\fR is omitted, either the existing script or the empty string is
omitted, the currently installed script is returned (or an empty
string if no such handler is installed).  The callback is only
performed if the event loop is being serviced (e.g. via \fBvwait\fR or
\fBupdate\fR).
returned.  For handlers to be processed, the event loop must be entered, e.g.
via \fBvwait\fR or \fBupdate\fR, or by using Tk.
.RS
.PP
A file event handler is a binding between a channel and a script, such
that the script is evaluated whenever the channel becomes readable or
writable.  File event handlers are most commonly used to allow data to
be received from another process on an event-driven basis, so that the
\fIscript\fR is evaluated at the global level in the interpreter it was
established in.  Any resulting error is handled in the background, i.e. via
\fBinterp bgerror\fR.  In order to prevent an endless loop due to a buggy
handler, the handler is deleted if \fIscript\fR returns an error so that it is
not evaluated again.
receiver can continue to interact with the user or with other channels
while waiting for the data to arrive.  If an application invokes
\fBchan gets\fR or \fBchan read\fR on a blocking channel when there is
no input data available, the process will block; until the input data
arrives, it will not be able to service other events, so it will
appear to the user to
.PP
Without an event handler, \fBchan gets\fR or \fBchan read\fR on \fIchannel\fR in
blocking mode may block until data becomes available, during which the
thread is unable to perform other work or respond to events on other channels.
This could cause the application to appear to
.QW "freeze up"
\&.
With \fBchan event\fR, the
process can tell when data is present and only invoke \fBchan gets\fR
or \fBchan read\fR when they will not block.
Channel event handlers allow events on \fIchannel\fR to direct channel handling
so that the reader or writer can continue to perform other processing while
waiting for a channel to become available and then handle channel operations
when the channel is ready for the operation.
.PP
A channel is considered to be readable if there is unread data
available on the underlying device.  A channel is also considered to
\fIchannel\fR is considered to be readable if there is unread data
available on the underlying device.  \fIchannel\fR is also considered to
be readable if there is unread data in an input buffer, except in the
special case where the most recent attempt to read from the channel
special case where the most recent attempt to read from \fIchannel\fR
was a \fBchan gets\fR call that could not find a complete line in the
input buffer.  This feature allows a file to be read a line at a time
in non-blocking mode using events.  A channel is also considered to be
readable if an end of file or error condition is present on the
underlying file or device.  It is important for \fIscript\fR to check
for these conditions and handle them appropriately; for example, if
there is no special check for end of file, an infinite loop may occur
where \fIscript\fR reads no data, returns, and is immediately invoked
again.
.PP
A channel is considered to be writable if at least one byte of data
can be written to the underlying file or device without blocking, or
\fIchannel\fR is considered to be writable if at least one byte of data can be
written to the underlying file or device without blocking, or if an error
if an error condition is present on the underlying file or device.
Note that client sockets opened in asynchronous mode become writable
when they become connected or if the connection fails.
condition is present. Note that client sockets opened in asynchronous mode
become writable when they become connected or if the connection fails.
.PP
Event-driven I/O works best for channels that have been placed into
non-blocking mode with the \fBchan configure\fR command.  In blocking
Event-driven channel handling works best for channels in non-blocking mode.  In
blocking mode \fIchannel\fR blocks when \fBchan puts\fR writes more data than
mode, a \fBchan puts\fR command may block if you give it more data
than the underlying file or device can accept, and a \fBchan gets\fR
or \fBchan read\fR command will block if you attempt to read more data
than is ready; no events will be processed while the commands block.
In non-blocking mode \fBchan puts\fR, \fBchan read\fR, and \fBchan
\fIchannel\fR can accept at the moment, and also when \fBchan gets\fR or
\fBchan read\fR requests more data than is currently available.  When
\fIchannel\fR blocks, the thread can not do any other processing or service any
other events.  When \fIchannel\fR is in non-blocking mode a thread may to carry
gets\fR never block.
.PP
The script for a file event is executed at global level (outside the
context of any Tcl procedure) in the interpreter in which the \fBchan
event\fR command was invoked.  If an error occurs while executing the
script then the command registered with \fBinterp bgerror\fR is used
to report the error.  In addition, the file event handler is deleted
if it ever returns an error; this is done in order to prevent infinite
loops due to buggy handlers.
on with other work and get back to \fIchannel\fR at the right time.
.RE
.\" METHOD: flush
.TP
\fBchan flush \fIchannel\fR
.
Ensures that all pending output for the channel called \fIchannel\fR
is written.
.RS
.PP
If the channel is in blocking mode the command does not return until
If \fIchannel\fR is in blocking mode, flushes all buffered output to the
all the buffered output has been flushed to the channel. If the
channel is in non-blocking mode, the command may return before all
buffered output has been flushed; the remainder will be flushed in the
destination and then returns.  If \fIchannel\fR is non-blocking, returns
immediately while all buffered output is flushed in the background as soon as
background as fast as the underlying file or device is able to absorb
it.
possible.
.RE
.\" METHOD: gets
.TP
\fBchan gets \fIchannel\fR ?\fIvarName\fR?
.
Reads a line from the channel consisting of all characters up to the next
end-of-line sequence or until end of file is seen. The line feed character
Reads and returns the characters up to but not including the next end\-of\-line
representation or the end of the input, whichever comes first. If \fIvarName\fR
corresponding to end-of-line sequence is not included as part of the line.
If the \fIvarName\fR argument is specified, the line is stored in the variable
of that name and the command returns the length of the line. If \fIvarName\fR
is given, stores the result in the variable named \fIvarName\fR and returns the
length of the line.  If the line was terminated by the end of the input rather
is not specified, the command returns the line itself as the result of the command.
.RS
.PP
If a complete line is not available and the channel is not at EOF, the command
will block in the case of a blocking channel. For non-blocking channels, the
command will return the empty string as the result in the case of \fIvarName\fR
not specified and -1 if it is.
.RE
.RS
.PP
If a blocking channel is already at EOF, the command returns an empty string if
\fIvarName\fR is not specified. Note an empty string result can also be returned
when a blank line (no characters before the next end of line sequence). The two
cases can be distinguished by calling the \fBchan eof\fR command to check for
end of file. If \fIvarName\fR is specified, the command returns -1 on end of file.
than an end-of-line representation, a subsequent call to \fBchan eof\fR returns
1.  If more input is needed and \fIchannel\fR is non-blocking, returns the
empty string or if \fIvarName\fR was given returns \-1.
There is no ambiguity in this case because blank lines result in 0 being returned.
.RE
.RS
.PP
If a non-blocking channel is already at EOF, the command returns an empty line
if \fIvarName\fR is not specified. This can be distinguished from an empty line
If necessary use \fIvarName\fR along with a return value of 0 to determine that
being returned by either a blank line being read or a full line not being available
through the use of the \fBchan eof\fR and \fBchan blocked\fR commands. If
a line is actually empty, as opposed to more input being needed to provide a
complete line.  \fBchan eof\fR can then be used to determine whether more input
\fBchan eof\fR returns true, the channel is at EOF. If \fBchan blocked\fR returns
true, a full line was not available. If both commands return false, an empty
line was read. If \fIvarName\fR was specified for a non-bocking channel at EOF,
the command returns -1. This can be distinguished from full line not being
available either by \fBchan eof\fR or \fBchan blocked\fR as above. Note that
when \fIvarName\fR is specified, there is no need to distinguish between eof
and blank lines as the latter will result in the command returning 0.
is forthcoming.
.PP
If the encoding profile \fBstrict\fR is in effect for the channel, the command
will raise an exception with the POSIX error code \fBEILSEQ\fR if any encoding
Returns an error with the POSIX error code \fBEILSEQ\fR if the encoding profile
errors are encountered in the channel input data. The file pointer remains
unchanged and it is possible to introspect, and in some cases recover, by
changing the encoding in use. See \fBENCODING ERROR EXAMPLES\fR later.
for \fIchannel\fR is \fBstrict\fR and a decoding error occurs, in which case
the current position is unchanged and it may be possible to change the encoding
and continue to read the input.  See \fBENCODING ERROR EXAMPLES\fR later.
.RE
.\" METHOD: isbinary
.TP
\fBchan isbinary \fIchannel\fR
.
Test whether the channel called \fIchannel\fR is a binary channel,
returning 1 if it is and, and 0 otherwise. A binary channel is
a channel with iso8859-1 encoding, -eofchar set to {} and
Returns 1 if \fIchannel\fR is configured as described for \fB-translation
binary\fR, and 0 otherwise.

-translation set to lf.
.\" METHOD: names
.TP
\fBchan names\fR ?\fIpattern\fR?
.
Produces a list of all channel names. If \fIpattern\fR is specified,
Returns a list of all channel names, or if \fIpattern\fR is given, only those
only those channel names that match it (according to the rules of
\fBstring match\fR) will be returned.
names that match according to the rules of \fBstring match\fR.
.\" METHOD: pending
.TP
\fBchan pending \fImode channel\fR
.
Depending on whether \fImode\fR is \fBinput\fR or \fBoutput\fR,
returns the number of
bytes of input or output (respectively) currently buffered
internally for \fIchannel\fR (especially useful in a readable event
callback to impose application-specific limits on input line lengths to avoid
a potential denial-of-service attack where a hostile user crafts
an extremely long line that exceeds the available memory to buffer it).
Returns -1 if the channel was not opened for the mode in question.
Returns the number of bytes of input
when \fImode\fR is
.QW\fBinput\fR
, or output when \fImode\fR is
.QW\fBoutput\fR
, that are currently internally buffered for \fIchannel\fR.  Useful in a readable
event callback to impose limits on input line length to avoid a potential
denial-of-service attack where an extremely long line exceeds the available
memory to buffer it.  Returns -1 if \fIchannel\fR was not opened for the mode in
question.
.\" METHOD: pipe
.TP
\fBchan pipe\fR
.
Creates a standalone pipe whose read- and write-side channels are
returned as a 2-element list, the first element being the read side and
Creates a pipe, i.e. a readable channel and a writable channel, and returns the
names of these channels. Data written to the writable channel can be read from
the readable channel.  Because the pipe is a real system-level pipe, it can be
the second the write side. Can be useful e.g. to redirect
separately \fBstderr\fR and \fBstdout\fR from a subprocess. To do
this, spawn with "2>@" or
connected to other processes using redirection.  For example, to redirect
\fBstderr\fR from a subprocess into one channel, and \fBstdout\fR into another,
\fBexec\fR with "2>@" and ">@", each onto the writable side of a pipe, closing
">@" redirection operators onto the write side of a pipe, and then
immediately close it in the parent. This is necessary to get an EOF on
the read side once the child has exited or otherwise closed its output.
the writable side immediately thereafter so that EOF is signaled on the read
side once the subprocess has closed its output, typically on exit.
.RS
.PP
Note that the pipe buffering semantics can vary at the operating system level
substantially; it is not safe to assume that a write performed on the output
side of the pipe will appear instantly to the input side. This is a
Due to buffering, data written to one side of a pipe might not immediately
become available on the other side.  Tcl's own buffers can be configured via
\fBchan configure -buffering\fR, but overall behaviour still depends on
operating system buffers outside of Tcl's control. Once the write side of the
fundamental difference and Tcl cannot conceal it. The overall stream semantics
\fIare\fR compatible, so blocking reads and writes will not see most of the
differences, but the details of what exactly gets written when are not. This
is most likely to show up when using pipelines for testing; care should be
taken to ensure that deadlocks do not occur and that potential short reads are
channel is closed, any data remaining in the buffers is flushed through to the
read side.  It may be useful to arrange for the connected process to flush at
some point after writing to the channel or to have it use some system-provided
mechanism to configure buffering.  When two pipes are connected to the same
process, one to send data to the process, and one to read data from the
process, a deadlock may occur if the channels are in blocking mode:  If
allowed for.
reading, the channel may block waiting for data that can never come because
buffers are only flushed on subsequent writes, and if writing, the channel may
block while waiting for the buffers to become free, which can never happen
because the reader can not read while the writer is blocking.  To avoid this
issue, either put the channels into non-blocking mode and use event handlers,
or place the read channel and the write channel in separate interpreters in
separate threads.
.RE
.\" METHOD: pop
.TP
\fBchan pop \fIchannel\fR
.
Removes the topmost transformation from the channel \fIchannel\fR, if there
Removes the topmost transformation handler from \fIchannel\fR if there is one,
is any. If there are no transformations added to \fIchannel\fR, this is
equivalent to \fBchan close\fR of that channel. The result is normally the
empty string, but can be an error in some situations (i.e. where the
underlying system stream is closed and that results in an error).
and closes \fIchannel\fR otherwise. The result is normally the empty string,
but may be an error in some situations, e.g. when closing the underlying
resource results in an error.
.\" METHOD: postevent
.TP
\fBchan postevent \fIchannel eventSpec\fR
.
This subcommand is used by command handlers specified with \fBchan
For use by handlers established with \fBchan create\fR.  Notifies Tcl that
create\fR. It notifies the channel represented by the handle
\fIchannel\fR that the event(s) listed in the \fIeventSpec\fR have
occurred. The argument has to be a list containing any of the strings
\fBread\fR and \fBwrite\fR. The list must contain at least one
that one or more event(s) listed in \fIeventSpec\fR, each of which is either
.QW\fBread\fR
or
.QW\fBwrite\fR.
element as it does not make sense to invoke the command if there are
no events to post.
, have occurred.
.RS
.PP
Note that this subcommand can only be used with channel handles that
were created/opened by \fBchan create\fR. All other channels will
For use only by handlers for \fIchannel\fR which must have been created by
\fBchan create\fR.  It is an error to post an event for any other kind of
cause this subcommand to report an error.
channel.
.PP
As only the Tcl level of a channel, i.e. its command handler, should
post events to it we also restrict the usage of this command to the
interpreter that created the channel. In other words, posting events
to a reflected channel from an interpreter that does not contain it's
implementation is not allowed. Attempting to post an event from any
Since only the handlers for a reflected channel should post events it is
an error to post an event from any interpreter other than the interpreter that
other interpreter will cause this subcommand to report an error.
created the channel.
.PP
Another restriction is that it is not possible to post events that the
I/O core has not registered an interest in. Trying to do so will cause
the method to throw an error. See the command handler method
\fBwatch\fR described in \fBrefchan\fR, the document specifying
It is an error to post an event that \fIchannel\fR has no interest in.  See
\fBwatch\fR in the \fBrefchan\fR documentation for more information
the API of command handlers for reflected channels.
.PP
This command is \fBsafe\fR and made accessible to safe interpreters.
It can trigger the execution of \fBchan event\fR handlers, whether in the
current interpreter or in other interpreters or other threads, even
where the event is posted from a safe interpreter and listened for by
a trusted interpreter. \fBChan event\fR handlers are \fIalways\fR
executed in the interpreter that set them up.
\fBchan postevent\fR is available in safe interpreters, as any handler for a
reflected channel would have been created, and will be evaluated in that
interpreter as well.
.RE
.\" METHOD: push
.TP
\fBchan push \fIchannel cmdPrefix\fR
.
Adds a new transformation on top of the channel \fIchannel\fR. The
Adds a new transformation handler on top of \fIchannel\fR and returns a handle
\fIcmdPrefix\fR argument describes a list of one or more words which represent
a handler that will be used to implement the transformation. The command
prefix must provide the API described in the \fBtranschan\fR manual page.
for the transformation.  \fIcmdPrefix\fR is the first words of a command that
provides the interface documented for \fBtranschan\fR, and transforms data on
The result of this subcommand is a handle to the transformation. Note that it
is important to make sure that the transformation is capable of supporting the
channel mode that it is used with or this can make the channel neither
\fIchannel\fR, It is an error if handler does not support the mode(s)
\fIchannel\fR is in.
readable nor writable.
.\" METHOD: puts
.TP
\fBchan puts\fR ?\fB\-nonewline\fR? ?\fIchannel\fR? \fIstring\fR
.
Writes \fIstring\fR to the channel named \fIchannel\fR followed by a
newline character. A trailing newline character is written unless the
Writes \fIstring\fR and a line feed to \fIchannel\fR.  If \fB\-nonewline\fR is
given, the trailing line feed is not written. The default channel is
optional flag \fB\-nonewline\fR is given. If \fIchannel\fR is
omitted, the string is written to the standard output channel,
\fBstdout\fR.
.RS
.PP
Newline characters in the output are translated by \fBchan puts\fR to
Each line feed in the output is translated to the appropriate end of line
platform-specific end-of-line sequences according to the currently
configured value of the \fB\-translation\fR option for the channel
sequence as per the \fB\-translation\fR configuration setting of \fIchannel\fR.
(for example, on PCs newlines are normally replaced with
carriage-return-linefeed sequences; see \fBchan configure\fR above for
details).
.PP
Tcl buffers output internally, so characters written with \fBchan
puts\fR may not appear immediately on the output file or device; Tcl
will normally delay output until the buffer is full or the channel is
Because Tcl internally buffers output, characters written to \fIchannel\fR may not
immediately be available at the destination.  Tcl normally delays output until
the buffer is full or \fIchannel\fR is closed. \fBchan flush\fR forces output in
closed.  You can force output to appear immediately with the \fBchan
flush\fR command.
the direction of the destination.
.PP
When the output buffer fills up, the \fBchan puts\fR command will
If \fIchannel\fR is in blocking mode and the write buffer fills up, blocks
normally block until all the buffered data has been accepted for
output by the operating system.  If \fIchannel\fR is in non-blocking
until space in the buffer is available again. If \fIchannel\fR is in 
mode then the \fBchan puts\fR command will not block even if the
operating system cannot accept the data.  Instead, Tcl continues to
buffer the data and writes it in the background as fast as the
underlying file or device can accept it.  The application must use the
Tcl event loop for non-blocking output to work; otherwise Tcl never
non-blocking mode, returns immediately and the data is written in the
background as fast possible, constrained by the speed at which the
destination accepts it. Data written to a channel in non-blocking mode can only
actually be written to the underlying resource when the application enters the
event loop so that channel events can be processed. When a channel is in
finds out that the file or device is ready for more output data.  It
is possible for an arbitrarily large amount of data to be buffered for
a channel in non-blocking mode, which could consume a large amount of
memory.  To avoid wasting memory, non-blocking I/O should normally be
used in an event-driven fashion with the \fBchan event\fR command
(do not invoke \fBchan puts\fR unless you have recently been notified
via a file event that the channel is ready for more output data).
non-blocking mode, Tcl's internal buffers can hold an arbitrary amount of data,
possibly consuming a large amount of memory. To avoid wasting memory, channels
in non-blocking mode should normally be handled using \fBchan event\fR, where
the application only invokes \fBchan puts\fR after being notified through a
file event handler that the channel is ready for more output data.
.PP
The command will raise an error exception with POSIX error code \fBEILSEQ\fR if
Returns an error with POSIX error code \fBEILSEQ\fR if the encoding profile of
the encoding profile \fBstrict\fR is in effect for the channel and the output
data cannot be encoded in the encoding configured for the channel. Data
may be partially written to the channel in this case.
\fIchannel\fR is \fBstrict\fR and the data cannot be encoded in the encoding
for the channel. The data that were successfully encoded up to the point of
error may be written to the channel.
.RE
.\" METHOD: read
.TP
\fBchan read \fIchannel\fR ?\fInumChars\fR?
.TP
\fBchan read \fR?\fB\-nonewline\fR? \fIchannel\fR
.
In the first form, the result will be the next \fInumChars\fR
Reads and returns the next \fInumChars\fR characters from \fIchannel\fR. If
characters read from the channel named \fIchannel\fR; if
\fInumChars\fR is omitted, all characters up to the point when the
channel would signal a failure (whether an end-of-file, blocked or
other error condition) are read. In the second form (i.e. when
\fInumChars\fR has been omitted) the flag \fB\-nonewline\fR may be
given to indicate that any trailing newline in the string that has
\fInumChars\fR is omitted, all available characters up to the end of the file
are read, or if \fIchannel\fR is in non-blocking mode, all currently-available
characters are read.  If there is an error on \fIchannel\fR, reading ceases and
an error is returned.  If \fInumChars\fR is not given, \fB\-nonewline\fR
may be given, causing any trailing line feed to be trimmed.
been read should be trimmed.
.RS
.PP
If \fIchannel\fR is in non-blocking mode, \fBchan read\fR may not
If \fIchannel\fR is in non-blocking mode, fewer characters than requested may be
read as many characters as requested: once all available input has
been read, the command will return the data that is available rather
than blocking for more input.  If the channel is configured to use a
returned.  If \fIchannel\fR is configured to use a multi-byte encoding, bytes
multi-byte encoding, then there may actually be some bytes remaining
in the internal buffers that do not form a complete character.  These
bytes will not be returned until a complete character is available or
end-of-file is reached.  The \fB\-nonewline\fR switch is ignored if
the command returns before reaching the end of the file.
that do not form a complete character are retained in the buffers until enough
bytes to complete the character accumulate, or the end of the data is reached.
\fB\-nonewline\fR is ignored if characters are returned before reaching the end
of the file.
.PP
\fBChan read\fR translates end-of-line sequences in the input into
newline characters according to the \fB\-translation\fR option for the
Each end-of-line sequence according to the value of \fB\-translation\fR is
translated into a line feed.
channel (see \fBchan configure\fR above for a discussion on the ways
in which \fBchan configure\fR will alter input).
.PP
When reading from a serial port, most applications should configure
When reading from a serial port, most applications should configure the channel
the serial port channel to be non-blocking, like this:
.PP
.CS
\fBchan configure \fIchannel \fB\-blocking \fI0\fR.
to be in non-blocking mode, but not necessarily use an event handler since most
.CE
.PP
Then \fBchan read\fR behaves much like described above.  Note that
most serial ports are comparatively slow; it is entirely possible to
get a \fBreadable\fR event for each character read from them. Care
must be taken when using \fBchan read\fR on blocking serial ports:
serial ports are comparatively slow.  It is entirely possible to get a
\fBreadable\fR event for each individual character.  In blocking mode, \fBchan
read\fR blocks forever when reading to the end of the data if there is no
.TP
\fBchan read \fIchannel numChars\fR
.
In this form \fBchan read\fR blocks until \fInumChars\fR have been
received from the serial port.
.TP
\fBchan read \fIchannel\fR
.
In this form \fBchan read\fR blocks until the reception of the
end-of-file character, see \fBchan configure -eofchar\fR. If there no
\fBchan configure -eofchar\fR configured for the channel.
end-of-file character has been configured for the channel, then
\fBchan read\fR will block forever.
.PP
If the encoding profile \fBstrict\fR is in effect for the channel, the command
will raise an exception with the POSIX error code \fBEILSEQ\fR if any encoding
If the encoding profile for \fIchannel\fR is \fBstrict\fR, raises an exception
with the POSIX error code \fBEILSEQ\fR if a decoding error is encountered when
errors are encountered in the channel input data. If the channel is in blocking
mode, the error is thrown after advancing the file pointer to the beginning of
the invalid data. The successfully decoded leading portion of the data prior to
the error location is returned as the value of the \fB\-data\fR key of the error
option dictionary. If the channel is in non-blocking mode, the successfully
reading. If \fIchannel\fR is blocking , advances the file pointer to the
beginning of the invalid input and returns the error. The input that was
successfully-decoded up to the first byte that resulted in an error is
available in as the \fB\-result read\fR entry in the error option dictionary.
If \fIchannel\fR is in non-blocking mode, returns the successfully-decoded
decoded portion of data is returned by the command without an error
exception being raised. A subsequent read will start at the invalid data
and immediately raise a \fBEILSEQ\fR POSIX error exception. Unlike the
blocking channel case, the \fB\-data\fR key is not present in the
error option dictionary. In the case of exception thrown due to encoding
input.  A subsequent read starts at the position of the invalid data
and raises a \fBEILSEQ\fR POSIX error exception. Unlike the blocking channel
case, the \fB\-result read\fR key is not present in the error option
dictionary. It may be possible to change the encoding for \fIchannel\fR in
errors, it is possible to introspect, and in some cases recover, by
changing the encoding in use. See \fBENCODING ERROR EXAMPLES\fR later.
order to read the input that previously resulted in the decoding error. See
\fBENCODING ERROR EXAMPLES\fR later.
.RE
.\" METHOD: seek
.RE .\" METHOD: seek
.TP
\fBchan seek \fIchannel offset\fR ?\fIorigin\fR?
.
Sets the current access position within the underlying data stream for
the channel named \fIchannel\fR to be \fIoffset\fR bytes relative to
\fIorigin\fR. \fIOffset\fR must be an integer (which may be negative)
and \fIorigin\fR must be one of the following:
Sets the current position in \fIchannel\fR to integer \fIoffset\fR
bytes relative to \fIorigin\fR.  A negative offset moves the current position
backwards from the origin.  \fIorigin\fR is one of the
following:
.RS
.IP \fBstart\fR
The new access position will be \fIoffset\fR bytes from the start
The origin is the start of the data.  This is the default.
of the underlying file or device.
.IP \fBcurrent\fR
The new access position will be \fIoffset\fR bytes from the current
The origin is the current position.
access position; a negative \fIoffset\fR moves the access position
backwards in the underlying file or device.
.IP \fBend\fR
The new access position will be \fIoffset\fR bytes from the end of the
file or device.  A negative \fIoffset\fR places the access position
before the end of file, and a positive \fIoffset\fR places the access
position after the end of file.
The origin is the end of the data.
.PP
The \fIorigin\fR argument defaults to \fBstart\fR.
.PP
\fBChan seek\fR flushes all buffered output for the channel before the
\fBChan seek\fR flushes all buffered output even if \fIchannel\fR is in
command returns, even if the channel is in non-blocking mode.  It also
discards any buffered and unread input.  This command returns an empty
non-blocking mode, discards any buffered and unread input, and returns the
string.  An error occurs if this command is applied to channels whose
underlying file or device does not support seeking.
empty string or an error if \fIchannel\fR does not support seeking.
.PP
Note that \fIoffset\fR values are byte offsets, not character offsets.
Both \fBchan seek\fR and \fBchan tell\fR operate in terms of bytes,
not characters, unlike \fBchan read\fR.
\fIoffset\fR values are byte offsets, not character offsets.  Unlike \fBchan
read\fR, both \fBchan seek\fR and \fBchan tell\fR operate in terms of bytes,
not characters,
.RE
.\" METHOD: tell
.TP
\fBchan tell \fIchannel\fR
.
Returns a number giving the current access position within the
underlying data stream for the channel named \fIchannel\fR. This
value returned is a byte offset that can be passed to \fBchan seek\fR
in order to set the channel to a particular position.  Note that this
Returns the offset in bytes of the current position in the underlying data, or
-1 if \fIchannel\fR does not support seeking. The value can be passed to \fBchan
seek\fR to set current position to that offset.
value is in terms of bytes, not characters like \fBchan read\fR.  The
value returned is -1 for channels that do not support seeking.
.\" METHOD: truncate
.TP
\fBchan truncate \fIchannel\fR ?\fIlength\fR?
.
Sets the byte length of the underlying data stream for the channel
named \fIchannel\fR to be \fIlength\fR (or to the current byte
offset within the underlying data stream if \fIlength\fR is
Flushes \fIchannel\fR and truncates the data in \fIchannel\fR to \fIlength\fR
bytes, or to the current position in bytes if \fIlength\fR is omitted.
omitted). The channel is flushed before truncation.
.
.SH EXAMPLES
.SS "SIMPLE CHANNEL OPERATION EXAMPLES"
.PP
Instruct Tcl to always send output to \fBstdout\fR immediately,
whether or not it is to a terminal:
.PP