'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
-'\" RCS: @(#) $Id: TraceVar.3,v 1.8 2002/08/05 03:24:39 dgp Exp $
-'\"
-'\" The 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?
-'\" Give maximum sizes of arguments for setting tab stops. Type and
-'\" name are examples of largest possible arguments that will be passed
-'\" to .AP later. If args are omitted, default tab stops are used.
-'\"
-'\" .BS
-'\" Start box enclosure. From here until next .BE, everything will be
-'\" enclosed in one large box.
-'\"
-'\" .BE
-'\" End of box enclosure.
-'\"
-'\" .CS
-'\" Begin code excerpt.
-'\"
-'\" .CE
-'\" End code excerpt.
-'\"
-'\" .VS ?version? ?br?
-'\" Begin vertical sidebar, for use in marking newly-changed parts
-'\" 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.
-'\"
-'\" .VE
-'\" End of vertical sidebar.
-'\"
-'\" .DS
-'\" Begin an indented unfilled display.
-'\"
-'\" .DE
-'\" End of indented unfilled display.
-'\"
-'\" .SO
-'\" Start of list of standard options for a Tk widget. The
-'\" options follow on successive lines, in four 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.
-'\"
-'\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $
-'\"
-'\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
+.TH Tcl_TraceVar 3 7.4 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?
+.\" Give maximum sizes of arguments for setting tab stops. Type and
+.\" name are examples of largest possible arguments that will be passed
+.\" to .AP later. If args are omitted, default tab stops are used.
+.\"
+.\" .BS
+.\" Start box enclosure. From here until next .BE, everything will be
+.\" enclosed in one large box.
+.\"
+.\" .BE
+.\" End of box enclosure.
+.\"
+.\" .CS
+.\" Begin code excerpt.
+.\"
+.\" .CE
+.\" End code excerpt.
+.\"
+.\" .VS ?version? ?br?
+.\" Begin vertical sidebar, for use in marking newly-changed parts
+.\" 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.
+.\"
+.\" .VE
+.\" End of vertical sidebar.
+.\"
+.\" .DS
+.\" Begin an indented unfilled display.
+.\"
+.\" .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
+.\" # Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.\}
.ta \\n()Au \\n()Bu
.ie !"\\$3"" \{\
-\&\\$1 \\fI\\$2\\fP (\\$3)
+\&\\$1 \\fI\\$2\\fP (\\$3)
.\".b
.\}
.el \{\
.\}
.\}
..
-'\" # define tabbing values for .AP
+.\" # define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+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
+.\" # BS - start boxed text
+.\" # ^y = starting y location
+.\" # ^b = 1
.de BS
.br
.mk ^y
.if n \l'\\n(.lu\(ul'
.if n .fi
..
-'\" # BE - end boxed text (draw box now)
+.\" # BE - end boxed text (draw box now)
.de BE
.nf
.ti 0
.br
.nr ^b 0
..
-'\" # VS - start vertical sidebar
-'\" # ^Y = starting y location
-'\" # ^v = 1 (for troff; for nroff this doesn't matter)
+.\" # 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
+.\" # VE - end of vertical sidebar
.de VE
.ie n 'mc
.el \{\
.\}
.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.
+.\" # 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
.mk ^Y
.\}
..
-'\" # DS - begin display
+.\" # DS - begin display
.de DS
.RS
.nf
.sp
..
-'\" # DE - end display
+.\" # DE - end display
.de DE
.fi
.RE
.sp
..
-'\" # SO - start of list of standard options
+.\" # 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
+.\" # SE - end of list of standard options
.de SE
.fi
.ft R
.LP
-See the \\fBoptions\\fR manual entry for details on the standard options.
+See the \\*(So manual entry for details on the standard options.
..
-'\" # OP - start of full description for a single option
+.\" # OP - start of full description for a single option
.de OP
.LP
.nf
.fi
.IP
..
-'\" # CS - begin code excerpt
+.\" # CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
-'\" # CE - end code excerpt
+.\" # CE - end code excerpt
.de CE
.fi
.RE
..
+.\" # UL - underline word
.de UL
\\$1\l'|0\(ul'\\$2
..
-.TH Tcl_TraceVar 3 7.4 Tcl "Tcl Library Procedures"
+.\" # 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_TraceVar, Tcl_TraceVar2, Tcl_UntraceVar, Tcl_UntraceVar2, Tcl_VarTraceInfo, Tcl_VarTraceInfo2 \- monitor accesses to a variable
.AS Tcl_VarTraceProc prevClientData
.AP Tcl_Interp *interp in
Interpreter containing variable.
-.AP "CONST char" *varName in
+.AP "const char" *varName in
Name of variable. May refer to a scalar variable, to
an array variable with no index, or to an array variable
with a parenthesized index.
.AP int flags in
-OR-ed combination of the values TCL_TRACE_READS, TCL_TRACE_WRITES,
-TCL_TRACE_UNSETS, TCL_TRACE_ARRAY, TCL_GLOBAL_ONLY, TCL_NAMESPACE_ONLY,
-TCL_TRACE_RESULT_DYNAMIC and TCL_TRACE_RESULT_OBJECT.
+OR-ed combination of the values \fBTCL_TRACE_READS\fR,
+\fBTCL_TRACE_WRITES\fR, \fBTCL_TRACE_UNSETS\fR, \fBTCL_TRACE_ARRAY\fR,
+\fBTCL_GLOBAL_ONLY\fR, \fBTCL_NAMESPACE_ONLY\fR,
+\fBTCL_TRACE_RESULT_DYNAMIC\fR and \fBTCL_TRACE_RESULT_OBJECT\fR.
Not all flags are used by all
procedures. See below for more information.
.AP Tcl_VarTraceProc *proc in
Procedure to invoke whenever one of the traced operations occurs.
.AP ClientData clientData in
Arbitrary one-word value to pass to \fIproc\fR.
-.AP "CONST char" *name1 in
+.AP "const char" *name1 in
Name of scalar or array variable (without array index).
-.AP "CONST char" *name2 in
+.AP "const char" *name2 in
For a trace on an element of an array, gives the index of the
element. For traces on scalar variables or on whole arrays,
is NULL.
next trace. If NULL, this call will return information about first
trace.
.BE
-
.SH DESCRIPTION
.PP
\fBTcl_TraceVar\fR allows a C procedure to monitor and control
access to a Tcl variable, so that the C procedure is invoked
whenever the variable is read or written or unset.
If the trace is created successfully then \fBTcl_TraceVar\fR returns
-TCL_OK. If an error occurred (e.g. \fIvarName\fR specifies an element
-of an array, but the actual variable isn't an array) then TCL_ERROR
+\fBTCL_OK\fR. If an error occurred (e.g. \fIvarName\fR specifies an element
+of an array, but the actual variable is not an array) then \fBTCL_ERROR\fR
is returned and an error message is left in the interpreter's result.
.PP
The \fIflags\fR argument to \fBTcl_TraceVar\fR indicates when the
This gives the trace procedure a chance to update the array before
array names or array get is called. Note that this is called
before an array set, but that will trigger write traces.
-.VS 8.4
.TP
\fBTCL_TRACE_RESULT_DYNAMIC\fR
The result of invoking the \fIproc\fR is a dynamically allocated
string that will be released by the Tcl library via a call to
\fBckfree\fR. Must not be specified at the same time as
-TCL_TRACE_RESULT_OBJECT.
+\fBTCL_TRACE_RESULT_OBJECT\fR.
.TP
\fBTCL_TRACE_RESULT_OBJECT\fR
The result of invoking the \fIproc\fR is a Tcl_Obj* (cast to a char*)
with a reference count of at least one. The ownership of that
reference will be transferred to the Tcl core for release (when the
core has finished with it) via a call to \fBTcl_DecrRefCount\fR. Must
-not be specified at the same time as TCL_TRACE_RESULT_DYNAMIC.
-.VE 8.4
+not be specified at the same time as \fBTCL_TRACE_RESULT_DYNAMIC\fR.
.PP
Whenever one of the specified operations occurs on the variable,
\fIproc\fR will be invoked.
It should have arguments and result that match the type
\fBTcl_VarTraceProc\fR:
+.PP
.CS
-typedef char *Tcl_VarTraceProc(
- ClientData \fIclientData\fR,
- Tcl_Interp *\fIinterp\fR,
- char *\fIname1\fR,
- char *\fIname2\fR,
- int \fIflags\fR);
+typedef char *\fBTcl_VarTraceProc\fR(
+ ClientData \fIclientData\fR,
+ Tcl_Interp *\fIinterp\fR,
+ char *\fIname1\fR,
+ char *\fIname2\fR,
+ int \fIflags\fR);
.CE
+.PP
The \fIclientData\fR and \fIinterp\fR parameters will
have the same values as those passed to \fBTcl_TraceVar\fR when the
trace was created.
below for details).
\fIFlags\fR is an OR-ed combination of bits providing several
pieces of information.
-One of the bits TCL_TRACE_READS, TCL_TRACE_WRITES, TCL_TRACE_ARRAY,
-or TCL_TRACE_UNSETS
+One of the bits \fBTCL_TRACE_READS\fR, \fBTCL_TRACE_WRITES\fR,
+\fBTCL_TRACE_ARRAY\fR, or \fBTCL_TRACE_UNSETS\fR
will be set in \fIflags\fR to indicate which operation is being performed
on the variable.
-The bit TCL_GLOBAL_ONLY will be set whenever the variable being
+The bit \fBTCL_GLOBAL_ONLY\fR will be set whenever the variable being
accessed is a global one not accessible from the current level of
procedure call: the trace procedure will need to pass this flag
back to variable-related procedures like \fBTcl_GetVar\fR if it
attempts to access the variable.
-The bit TCL_NAMESPACE_ONLY will be set whenever the variable being
+The bit \fBTCL_NAMESPACE_ONLY\fR will be set whenever the variable being
accessed is a namespace one not accessible from the current level of
procedure call: the trace procedure will need to pass this flag
back to variable-related procedures like \fBTcl_GetVar\fR if it
attempts to access the variable.
-The bit TCL_TRACE_DESTROYED will be set in \fIflags\fR if the trace is
+The bit \fBTCL_TRACE_DESTROYED\fR will be set in \fIflags\fR if the trace is
about to be destroyed; this information may be useful to \fIproc\fR
so that it can clean up its own internal data structures (see
-the section TCL_TRACE_DESTROYED below for more details).
-Lastly, the bit TCL_INTERP_DESTROYED will be set if the entire
+the section \fBTCL_TRACE_DESTROYED\fR below for more details).
+Lastly, the bit \fBTCL_INTERP_DESTROYED\fR will be set if the entire
interpreter is being destroyed.
When this bit is set, \fIproc\fR must be especially careful in
-the things it does (see the section TCL_INTERP_DESTROYED below).
+the things it does (see the section \fBTCL_INTERP_DESTROYED\fR below).
The trace procedure's return value should normally be NULL; see
-ERROR RETURNS below for information on other possibilities.
+\fBERROR RETURNS\fR below for information on other possibilities.
.PP
\fBTcl_UntraceVar\fR may be used to remove a trace.
If the variable specified by \fIinterp\fR, \fIvarName\fR, and \fIflags\fR
The return value from \fBTcl_VarTraceInfo\fR is the \fIclientData\fR
associated with a particular trace.
The trace must be on the variable specified by the \fIinterp\fR,
-\fIvarName\fR, and \fIflags\fR arguments (only the TCL_GLOBAL_ONLY and
-TCL_NAMESPACE_ONLY bits from \fIflags\fR is used; other bits are
+\fIvarName\fR, and \fIflags\fR arguments (only the \fBTCL_GLOBAL_ONLY\fR and
+\fBTCL_NAMESPACE_ONLY\fR bits from \fIflags\fR is used; other bits are
ignored) and its trace procedure must the same as the \fIproc\fR
argument.
If the \fIprevClientData\fR argument is NULL then the return
value corresponds to the first (most recently created) matching
trace, or NULL if there are no matching traces.
-If the \fIprevClientData\fR argument isn't NULL, then it should
+If the \fIprevClientData\fR argument is not NULL, then it should
be the return value from a previous call to \fBTcl_VarTraceInfo\fR.
In this case, the new return value will correspond to the next
matching trace after the one whose \fIclientData\fR matches
or if there are no more matching traces after it.
This mechanism makes it possible to step through all of the
traces for a given variable that have the same \fIproc\fR.
-
.SH "TWO-PART NAMES"
.PP
The procedures \fBTcl_TraceVar2\fR, \fBTcl_UntraceVar2\fR, and
except that the name of the variable consists of two parts.
\fIName1\fR gives the name of a scalar variable or array,
and \fIname2\fR gives the name of an element within an array.
-.VS 8.1
When \fIname2\fR is NULL,
\fIname1\fR may contain both an array and an element name:
if the name contains an open parenthesis and ends with a
the characters before the first open
parenthesis are treated as the name of an array variable.
If \fIname2\fR is NULL and \fIname1\fR does not refer
-to an array element
-.VE
-it means that either the variable is
+to an array element it means that either the variable is
a scalar or the trace is to be set on the entire array rather
than an individual element (see WHOLE-ARRAY TRACES below for
more information).
-
-
.SH "ACCESSING VARIABLES DURING TRACES"
.PP
During read, write, and array traces, the
If new traces are set by unset trace procedures, these traces
will be invoked on accesses to the variable by the trace
procedures.
-
.SH "CALLBACK TIMING"
.PP
When read tracing has been specified for a variable, the trace
will be invoked whenever the variable is destroyed.
The traces will be called after the variable has been
completely unset.
-
.SH "WHOLE-ARRAY TRACES"
.PP
If a call to \fBTcl_TraceVar\fR or \fBTcl_TraceVar2\fR specifies
just once, with \fIname1\fR equal to the name of the array
and \fIname2\fR NULL; it will not be invoked once for each
element.
-
.SH "MULTIPLE TRACES"
.PP
It is possible for multiple traces to exist on the same variable.
If a read or write trace unsets the variable then all of the unset
traces will be invoked but the remainder of the read and write traces
will be skipped.
-
.SH "ERROR RETURNS"
.PP
Under normal conditions trace procedures should return NULL, indicating
error occurred.
The return value must be a pointer to a static character string
containing an error message,
-.VS 8.4
-unless (\fIexactly\fR one of) the TCL_TRACE_RESULT_DYNAMIC and
-TCL_TRACE_RESULT_OBJECT flags is set, which specify that the result is
+unless (\fIexactly\fR one of) the \fBTCL_TRACE_RESULT_DYNAMIC\fR and
+\fBTCL_TRACE_RESULT_OBJECT\fR flags is set, which specify that the result is
either a dynamic string (to be released with \fBckfree\fR) or a
Tcl_Obj* (cast to char* and to be released with
\fBTcl_DecrRefCount\fR) containing the error message.
-.VE 8.4
If a trace procedure returns an error, no further traces are
invoked for the access and the traced access aborts with the
given message.
write tracing.
During unset traces, the return value is ignored and all relevant
trace procedures will always be invoked.
-
.SH "RESTRICTIONS"
.PP
A trace procedure can be called at any time, even when there
-is a partially-formed result in the interpreter's result area. If
+is a partially formed result in the interpreter's result area. If
the trace procedure does anything that could damage this result (such
as calling \fBTcl_Eval\fR) then it must save the original values of
the interpreter's \fBresult\fR and \fBfreeProc\fR fields and restore
them before it returns.
-
.SH "UNDEFINED VARIABLES"
.PP
It is legal to set a trace on an undefined variable.
The variable will still appear to be undefined until the
first time its value is set.
If an undefined variable is traced and then unset, the unset will fail
-with an error (``no such variable''), but the trace
-procedure will still be invoked.
-
+with an error
+.PQ "no such variable" "" ,
+but the trace procedure will still be invoked.
.SH "TCL_TRACE_DESTROYED FLAG"
.PP
-In an unset callback to \fIproc\fR, the TCL_TRACE_DESTROYED bit
+In an unset callback to \fIproc\fR, the \fBTCL_TRACE_DESTROYED\fR bit
is set in \fIflags\fR if the trace is being removed as part
of the deletion.
Traces on a variable are always removed whenever the variable
-is deleted; the only time TCL_TRACE_DESTROYED isn't set is for
+is deleted; the only time \fBTCL_TRACE_DESTROYED\fR is not set is for
a whole-array trace invoked when only a single element of an
array is unset.
-
.SH "TCL_INTERP_DESTROYED"
.PP
When an interpreter is destroyed, unset traces are called for
all of its variables.
-The TCL_INTERP_DESTROYED bit will be set in the \fIflags\fR
+The \fBTCL_INTERP_DESTROYED\fR bit will be set in the \fIflags\fR
argument passed to the trace procedures.
Trace procedures must be extremely careful in what they do if
-the TCL_INTERP_DESTROYED bit is set.
+the \fBTCL_INTERP_DESTROYED\fR bit is set.
It is not safe for the procedures to invoke any Tcl procedures
on the interpreter, since its state is partially deleted.
All that trace procedures should do under these circumstances is
to clean up and free their own internal data structures.
-
.SH BUGS
.PP
-Tcl doesn't do any error checking to prevent trace procedures
-from misusing the interpreter during traces with TCL_INTERP_DESTROYED
+Tcl does not do any error checking to prevent trace procedures
+from misusing the interpreter during traces with \fBTCL_INTERP_DESTROYED\fR
set.
.PP
-Array traces are not yet integrated with the Tcl "info exists" command,
+Array traces are not yet integrated with the Tcl \fBinfo exists\fR command,
nor is there Tcl-level access to array traces.
-
+.SH "SEE ALSO"
+trace(n)
.SH KEYWORDS
clientData, trace, variable
OSDN Git Service
