'\"
'\" 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.
'\"
.TH Tcl_CreateCommand 3tcl "" Tcl "Tcl Library Procedures"
.\" The -*- nroff -*- definitions below are for supplemental macros used
.\" in Tcl/Tk manual entries.
.\"
.\" .AP type name in/out ?indent?
.\"	Start paragraph describing an argument to a library procedure.
.\"	type is type of argument (int, etc.), in/out is either "in", "out",
.\"	or "in/out" to describe whether procedure reads or modifies arg,
.\"	and indent is equivalent to second arg of .IP (shouldn't ever be
.\"	needed;  use .AS below instead)
.\"
.\" .AS ?type? ?name?
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.\"	name are examples of largest possible arguments that will be passed
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.\"
.\" .BS
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.\"	enclosed in one large box.
.\"
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.\" .CS
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.\"
.\" .VS ?version? ?br?
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.\"	of man pages.  The first argument is ignored and used for recording
.\"	the version when the .VS was added, so that the sidebars can be
.\"	found and removed when they reach a certain age.  If another argument
.\"	is present, then a line break is forced before starting the sidebar.
.\"
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.\"
.\" .DS
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.\"
.\" .DE
.\"	End of indented unfilled display.
.\"
.\" .SO ?manpage?
.\"	Start of list of standard options for a Tk widget. The manpage
.\"	argument defines where to look up the standard options; if
.\"	omitted, defaults to "options". The options follow on successive
.\"	lines, in three columns separated by tabs.
.\"
.\" .SE
.\"	End of list of standard options for a Tk widget.
.\"
.\" .OP cmdName dbName dbClass
.\"	Start of description of a specific option.  cmdName gives the
.\"	option's name as specified in the class command, dbName gives
.\"	the option's name in the option database, and dbClass gives
.\"	the option's class in the option database.
.\"
.\" .UL arg1 arg2
.\"	Print arg1 underlined, then print arg2 normally.
.\"
.\" .QW arg1 ?arg2?
.\"	Print arg1 in quotes, then arg2 normally (for trailing punctuation).
.\"
.\" .PQ arg1 ?arg2?
.\"	Print an open parenthesis, arg1 in quotes, then arg2 normally
.\"	(for trailing punctuation) and then a closing parenthesis.
.\"
.\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
.\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
\&\\$1 \\fI\\$2\\fP (\\$3)
.\".b
.\}
.el \{\
.br
.ie !"\\$2"" \{\
\&\\$1	\\fI\\$2\\fP
.\}
.el \{\
\&\\fI\\$1\\fP
.\}
.\}
..
.\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
.\"	# BS - start boxed text
.\"	# ^y = starting y location
.\"	# ^b = 1
.de BS
.br
.mk ^y
.nr ^b 1u
.if n .nf
.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
.\"	# BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.\}
.fi
.br
.nr ^b 0
..
.\"	# VS - start vertical sidebar
.\"	# ^Y = starting y location
.\"	# ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
.ie n 'mc \s12\(br\s0
.el .nr ^v 1u
..
.\"	# VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.ev 2
.nf
.ti 0
.mk ^t
\h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
.sp -1
.fi
.ev
.\}
.nr ^v 0
..
.\"	# Special macro to handle page bottom:  finish off current
.\"	# box/sidebar if in box/sidebar mode, then invoked standard
.\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"	Draw three-sided box if this is the box's first page,
.\"	draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
.bp
'fi
.ev
.if \\n(^b \{\
.mk ^y
.nr ^b 2
.\}
.if \\n(^v \{\
.mk ^Y
.\}
..
.\"	# DS - begin display
.de DS
.RS
.nf
.sp
..
.\"	# DE - end display
.de DE
.fi
.RE
.sp
..
.\"	# SO - start of list of standard options
.de SO
'ie '\\$1'' .ds So \\fBoptions\\fR
'el .ds So \\fB\\$1\\fR
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
.\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\*(So manual entry for details on the standard options.
..
.\"	# OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
..
.\"	# CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
.\"	# CE - end code excerpt
.de CE
.fi
.RE
..
.\"	# UL - underline word
.de UL
\\$1\l'|0\(ul'\\$2
..
.\"	# QW - apply quotation marks to word
.de QW
.ie '\\*(lq'"' ``\\$1''\\$2
.\"" fix emacs highlighting
.el \\*(lq\\$1\\*(rq\\$2
..
.\"	# PQ - apply parens and quotation marks to word
.de PQ
.ie '\\*(lq'"' (``\\$1''\\$2)\\$3
.\"" fix emacs highlighting
.el (\\*(lq\\$1\\*(rq\\$2)\\$3
..
.\"	# QR - quoted range
.de QR
.ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3
.\"" fix emacs highlighting
.el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3
..
.\"	# MT - "empty" string
.de MT
.QW ""
..
.BS
.SH NAME
Tcl_CreateCommand \- implement new commands in C
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_Command
\fBTcl_CreateCommand\fR(\fIinterp, cmdName, proc, clientData, deleteProc\fR)
.SH ARGUMENTS
.AS Tcl_CmdDeleteProc *deleteProc
.AP Tcl_Interp *interp in
Interpreter in which to create new command.
.AP "const char" *cmdName in
Name of command.
.AP Tcl_CmdProc *proc in
Implementation of new command:  \fIproc\fR will be called whenever
\fIcmdName\fR is invoked as a command.
.AP ClientData clientData in
Arbitrary one-word value to pass to \fIproc\fR and \fIdeleteProc\fR.
.AP Tcl_CmdDeleteProc *deleteProc in
Procedure to call before \fIcmdName\fR is deleted from the interpreter;
allows for command-specific cleanup.  If NULL, then no procedure is
called before the command is deleted.
.BE
.SH DESCRIPTION
.PP
\fBTcl_CreateCommand\fR defines a new command in \fIinterp\fR and associates
it with procedure \fIproc\fR such that whenever \fIcmdName\fR is
invoked as a Tcl command (via a call to \fBTcl_Eval\fR) the Tcl interpreter
will call \fIproc\fR to process the command.
It differs from \fBTcl_CreateObjCommand\fR in that a new string-based
command is defined;
that is, a command procedure is defined that takes an array of
argument strings instead of values.
The value-based command procedures registered by \fBTcl_CreateObjCommand\fR
can execute significantly faster than the string-based command procedures
defined by \fBTcl_CreateCommand\fR.
This is because they take Tcl values as arguments
and those values can retain an internal representation that
can be manipulated more efficiently.
Also, Tcl's interpreter now uses values internally.
In order to invoke a string-based command procedure
registered by \fBTcl_CreateCommand\fR,
it must generate and fetch a string representation
from each argument value before the call.
New commands should be defined using \fBTcl_CreateObjCommand\fR.
We support \fBTcl_CreateCommand\fR for backwards compatibility.
.PP
The procedures \fBTcl_DeleteCommand\fR, \fBTcl_GetCommandInfo\fR,
and \fBTcl_SetCommandInfo\fR are used in conjunction with
\fBTcl_CreateCommand\fR.
.PP
\fBTcl_CreateCommand\fR will delete an existing command \fIcmdName\fR,
if one is already associated with the interpreter.
It returns a token that may be used to refer
to the command in subsequent calls to \fBTcl_GetCommandName\fR.
If \fIcmdName\fR contains any \fB::\fR namespace qualifiers,
then the command is added to the specified namespace;
otherwise the command is added to the global namespace.
If \fBTcl_CreateCommand\fR is called for an interpreter that is in
the process of being deleted, then it does not create a new command
and it returns NULL.
\fIProc\fR should have arguments and result that match the type
\fBTcl_CmdProc\fR:
.PP
.CS
typedef int \fBTcl_CmdProc\fR(
        ClientData \fIclientData\fR,
        Tcl_Interp *\fIinterp\fR,
        int \fIargc\fR,
        const char *\fIargv\fR[]);
.CE
.PP
When \fIproc\fR is invoked the \fIclientData\fR and \fIinterp\fR
parameters will be copies of the \fIclientData\fR and \fIinterp\fR
arguments given to \fBTcl_CreateCommand\fR.
Typically, \fIclientData\fR points to an application-specific
data structure that describes what to do when the command procedure
is invoked.  \fIArgc\fR and \fIargv\fR describe the arguments to
the command, \fIargc\fR giving the number of arguments (including
the command name) and \fIargv\fR giving the values of the arguments
as strings.  The \fIargv\fR array will contain \fIargc\fR+1 values;
the first \fIargc\fR values point to the argument strings, and the
last value is NULL.
Note that the argument strings should not be modified as they may
point to constant strings or may be shared with other parts of the
interpreter.
.PP
Note that the argument strings are encoded in normalized UTF-8 since
version 8.1 of Tcl.
.PP
\fIProc\fR must return an integer code that is expected to be one of
\fBTCL_OK\fR, \fBTCL_ERROR\fR, \fBTCL_RETURN\fR, \fBTCL_BREAK\fR, or
\fBTCL_CONTINUE\fR.  See the Tcl overview man page
for details on what these codes mean.  Most normal commands will only
return \fBTCL_OK\fR or \fBTCL_ERROR\fR.  In addition, \fIproc\fR must set
the interpreter result;
in the case of a \fBTCL_OK\fR return code this gives the result
of the command, and in the case of \fBTCL_ERROR\fR it gives an error message.
The \fBTcl_SetResult\fR procedure provides an easy interface for setting
the return value;  for complete details on how the interpreter result
field is managed, see the \fBTcl_Interp\fR man page.
Before invoking a command procedure,
\fBTcl_Eval\fR sets the interpreter result to point to an empty string,
so simple commands can return an empty result by doing nothing at all.
.PP
The contents of the \fIargv\fR array belong to Tcl and are not
guaranteed to persist once \fIproc\fR returns:  \fIproc\fR should
not modify them, nor should it set the interpreter result to point
anywhere within the \fIargv\fR values.
Call \fBTcl_SetResult\fR with status \fBTCL_VOLATILE\fR if you want
to return something from the \fIargv\fR array.
.PP
\fIDeleteProc\fR will be invoked when (if) \fIcmdName\fR is deleted. This can
occur through a call to \fBTcl_DeleteCommand\fR or \fBTcl_DeleteInterp\fR,
or by replacing \fIcmdName\fR in another call to \fBTcl_CreateCommand\fR.
\fIDeleteProc\fR is invoked before the command is deleted, and gives the
application an opportunity to release any structures associated
with the command.  \fIDeleteProc\fR should have arguments and
result that match the type \fBTcl_CmdDeleteProc\fR:
.PP
.CS
typedef void \fBTcl_CmdDeleteProc\fR(
        ClientData \fIclientData\fR);
.CE
.PP
The \fIclientData\fR argument will be the same as the \fIclientData\fR
argument passed to \fBTcl_CreateCommand\fR.
.SH "SEE ALSO"
Tcl_CreateObjCommand, Tcl_DeleteCommand, Tcl_GetCommandInfo,
Tcl_SetCommandInfo, Tcl_GetCommandName, Tcl_SetObjResult
.SH KEYWORDS
bind, command, create, delete, interpreter, namespace