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1 | '\" |
2 | '\" Copyright (c) 1993 The Regents of the University of California. | |
3 | '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. | |
4 | '\" Copyright (c) 2000 Ajuba Solutions. | |
5 | '\" | |
6 | '\" See the file "license.terms" for information on usage and redistribution | |
7 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. | |
8 | '\" | |
9 | '\" RCS: @(#) $Id: trace.n,v 1.13.2.2 2004/10/27 14:43:14 dkf Exp $ | |
10 | '\" | |
11 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
12 | '\" manual entries. | |
13 | '\" | |
14 | '\" .AP type name in/out ?indent? | |
15 | '\" Start paragraph describing an argument to a library procedure. | |
16 | '\" type is type of argument (int, etc.), in/out is either "in", "out", | |
17 | '\" or "in/out" to describe whether procedure reads or modifies arg, | |
18 | '\" and indent is equivalent to second arg of .IP (shouldn't ever be | |
19 | '\" needed; use .AS below instead) | |
20 | '\" | |
21 | '\" .AS ?type? ?name? | |
22 | '\" Give maximum sizes of arguments for setting tab stops. Type and | |
23 | '\" name are examples of largest possible arguments that will be passed | |
24 | '\" to .AP later. If args are omitted, default tab stops are used. | |
25 | '\" | |
26 | '\" .BS | |
27 | '\" Start box enclosure. From here until next .BE, everything will be | |
28 | '\" enclosed in one large box. | |
29 | '\" | |
30 | '\" .BE | |
31 | '\" End of box enclosure. | |
32 | '\" | |
33 | '\" .CS | |
34 | '\" Begin code excerpt. | |
35 | '\" | |
36 | '\" .CE | |
37 | '\" End code excerpt. | |
38 | '\" | |
39 | '\" .VS ?version? ?br? | |
40 | '\" Begin vertical sidebar, for use in marking newly-changed parts | |
41 | '\" of man pages. The first argument is ignored and used for recording | |
42 | '\" the version when the .VS was added, so that the sidebars can be | |
43 | '\" found and removed when they reach a certain age. If another argument | |
44 | '\" is present, then a line break is forced before starting the sidebar. | |
45 | '\" | |
46 | '\" .VE | |
47 | '\" End of vertical sidebar. | |
48 | '\" | |
49 | '\" .DS | |
50 | '\" Begin an indented unfilled display. | |
51 | '\" | |
52 | '\" .DE | |
53 | '\" End of indented unfilled display. | |
54 | '\" | |
55 | '\" .SO | |
56 | '\" Start of list of standard options for a Tk widget. The | |
57 | '\" options follow on successive lines, in four columns separated | |
58 | '\" by tabs. | |
59 | '\" | |
60 | '\" .SE | |
61 | '\" End of list of standard options for a Tk widget. | |
62 | '\" | |
63 | '\" .OP cmdName dbName dbClass | |
64 | '\" Start of description of a specific option. cmdName gives the | |
65 | '\" option's name as specified in the class command, dbName gives | |
66 | '\" the option's name in the option database, and dbClass gives | |
67 | '\" the option's class in the option database. | |
68 | '\" | |
69 | '\" .UL arg1 arg2 | |
70 | '\" Print arg1 underlined, then print arg2 normally. | |
71 | '\" | |
72 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ | |
73 | '\" | |
74 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. | |
75 | .if t .wh -1.3i ^B | |
76 | .nr ^l \n(.l | |
77 | .ad b | |
78 | '\" # Start an argument description | |
79 | .de AP | |
80 | .ie !"\\$4"" .TP \\$4 | |
81 | .el \{\ | |
82 | . ie !"\\$2"" .TP \\n()Cu | |
83 | . el .TP 15 | |
84 | .\} | |
85 | .ta \\n()Au \\n()Bu | |
86 | .ie !"\\$3"" \{\ | |
87 | \&\\$1 \\fI\\$2\\fP (\\$3) | |
88 | .\".b | |
89 | .\} | |
90 | .el \{\ | |
91 | .br | |
92 | .ie !"\\$2"" \{\ | |
93 | \&\\$1 \\fI\\$2\\fP | |
94 | .\} | |
95 | .el \{\ | |
96 | \&\\fI\\$1\\fP | |
97 | .\} | |
98 | .\} | |
99 | .. | |
100 | '\" # define tabbing values for .AP | |
101 | .de AS | |
102 | .nr )A 10n | |
103 | .if !"\\$1"" .nr )A \\w'\\$1'u+3n | |
104 | .nr )B \\n()Au+15n | |
105 | .\" | |
106 | .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n | |
107 | .nr )C \\n()Bu+\\w'(in/out)'u+2n | |
108 | .. | |
109 | .AS Tcl_Interp Tcl_CreateInterp in/out | |
110 | '\" # BS - start boxed text | |
111 | '\" # ^y = starting y location | |
112 | '\" # ^b = 1 | |
113 | .de BS | |
114 | .br | |
115 | .mk ^y | |
116 | .nr ^b 1u | |
117 | .if n .nf | |
118 | .if n .ti 0 | |
119 | .if n \l'\\n(.lu\(ul' | |
120 | .if n .fi | |
121 | .. | |
122 | '\" # BE - end boxed text (draw box now) | |
123 | .de BE | |
124 | .nf | |
125 | .ti 0 | |
126 | .mk ^t | |
127 | .ie n \l'\\n(^lu\(ul' | |
128 | .el \{\ | |
129 | .\" Draw four-sided box normally, but don't draw top of | |
130 | .\" box if the box started on an earlier page. | |
131 | .ie !\\n(^b-1 \{\ | |
132 | \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' | |
133 | .\} | |
134 | .el \}\ | |
135 | \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' | |
136 | .\} | |
137 | .\} | |
138 | .fi | |
139 | .br | |
140 | .nr ^b 0 | |
141 | .. | |
142 | '\" # VS - start vertical sidebar | |
143 | '\" # ^Y = starting y location | |
144 | '\" # ^v = 1 (for troff; for nroff this doesn't matter) | |
145 | .de VS | |
146 | .if !"\\$2"" .br | |
147 | .mk ^Y | |
148 | .ie n 'mc \s12\(br\s0 | |
149 | .el .nr ^v 1u | |
150 | .. | |
151 | '\" # VE - end of vertical sidebar | |
152 | .de VE | |
153 | .ie n 'mc | |
154 | .el \{\ | |
155 | .ev 2 | |
156 | .nf | |
157 | .ti 0 | |
158 | .mk ^t | |
159 | \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' | |
160 | .sp -1 | |
161 | .fi | |
162 | .ev | |
163 | .\} | |
164 | .nr ^v 0 | |
165 | .. | |
166 | '\" # Special macro to handle page bottom: finish off current | |
167 | '\" # box/sidebar if in box/sidebar mode, then invoked standard | |
168 | '\" # page bottom macro. | |
169 | .de ^B | |
170 | .ev 2 | |
171 | 'ti 0 | |
172 | 'nf | |
173 | .mk ^t | |
174 | .if \\n(^b \{\ | |
175 | .\" Draw three-sided box if this is the box's first page, | |
176 | .\" draw two sides but no top otherwise. | |
177 | .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 | |
178 | .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c | |
179 | .\} | |
180 | .if \\n(^v \{\ | |
181 | .nr ^x \\n(^tu+1v-\\n(^Yu | |
182 | \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c | |
183 | .\} | |
184 | .bp | |
185 | 'fi | |
186 | .ev | |
187 | .if \\n(^b \{\ | |
188 | .mk ^y | |
189 | .nr ^b 2 | |
190 | .\} | |
191 | .if \\n(^v \{\ | |
192 | .mk ^Y | |
193 | .\} | |
194 | .. | |
195 | '\" # DS - begin display | |
196 | .de DS | |
197 | .RS | |
198 | .nf | |
199 | .sp | |
200 | .. | |
201 | '\" # DE - end display | |
202 | .de DE | |
203 | .fi | |
204 | .RE | |
205 | .sp | |
206 | .. | |
207 | '\" # SO - start of list of standard options | |
208 | .de SO | |
209 | .SH "STANDARD OPTIONS" | |
210 | .LP | |
211 | .nf | |
212 | .ta 5.5c 11c | |
213 | .ft B | |
214 | .. | |
215 | '\" # SE - end of list of standard options | |
216 | .de SE | |
217 | .fi | |
218 | .ft R | |
219 | .LP | |
220 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
221 | .. | |
222 | '\" # OP - start of full description for a single option | |
223 | .de OP | |
224 | .LP | |
225 | .nf | |
226 | .ta 4c | |
227 | Command-Line Name: \\fB\\$1\\fR | |
228 | Database Name: \\fB\\$2\\fR | |
229 | Database Class: \\fB\\$3\\fR | |
230 | .fi | |
231 | .IP | |
232 | .. | |
233 | '\" # CS - begin code excerpt | |
234 | .de CS | |
235 | .RS | |
236 | .nf | |
237 | .ta .25i .5i .75i 1i | |
238 | .. | |
239 | '\" # CE - end code excerpt | |
240 | .de CE | |
241 | .fi | |
242 | .RE | |
243 | .. | |
244 | .de UL | |
245 | \\$1\l'|0\(ul'\\$2 | |
246 | .. | |
247 | .TH trace n "8.4" Tcl "Tcl Built-In Commands" | |
248 | .BS | |
249 | '\" Note: do not modify the .SH NAME line immediately below! | |
250 | .SH NAME | |
251 | trace \- Monitor variable accesses, command usages and command executions | |
252 | .SH SYNOPSIS | |
253 | \fBtrace \fIoption\fR ?\fIarg arg ...\fR? | |
254 | .BE | |
255 | ||
256 | .SH DESCRIPTION | |
257 | .PP | |
258 | This command causes Tcl commands to be executed whenever certain operations are | |
259 | invoked. The legal \fIoption\fR's (which may be abbreviated) are: | |
260 | .TP | |
261 | \fBtrace add \fItype name ops ?args?\fR | |
262 | Where \fItype\fR is \fBcommand\fR, \fBexecution\fR, or \fBvariable\fR. | |
263 | .RS | |
264 | .TP | |
265 | \fBtrace add command\fR \fIname ops command\fR | |
266 | Arrange for \fIcommand\fR to be executed whenever command \fIname\fR | |
267 | is modified in one of the ways given by the list \fIops\fR. \fIName\fR will be | |
268 | resolved using the usual namespace resolution rules used by | |
269 | procedures. If the command does not exist, an error will be thrown. | |
270 | .RS | |
271 | .PP | |
272 | \fIOps\fR indicates which operations are of interest, and is a list of | |
273 | one or more of the following items: | |
274 | .TP | |
275 | \fBrename\fR | |
276 | Invoke \fIcommand\fR whenever the command is renamed. Note that | |
277 | renaming to the empty string is considered deletion, and will not | |
278 | be traced with '\fBrename\fR'. | |
279 | .TP | |
280 | \fBdelete\fR | |
281 | Invoke \fIcommand\fR when the command is deleted. Commands can be | |
282 | deleted explicitly by using the \fBrename\fR command to rename the | |
283 | command to an empty string. Commands are also deleted when the | |
284 | interpreter is deleted, but traces will not be invoked because there is no | |
285 | interpreter in which to execute them. | |
286 | .PP | |
287 | When the trace triggers, depending on the operations being traced, a | |
288 | number of arguments are appended to \fIcommand\fR so that the actual | |
289 | command is as follows: | |
290 | .CS | |
291 | \fIcommand oldName newName op\fR | |
292 | .CE | |
293 | \fIOldName\fR and \fInewName\fR give the traced command's current | |
294 | (old) name, and the name to which it is being renamed (the empty | |
295 | string if this is a 'delete' operation). | |
296 | \fIOp\fR indicates what operation is being performed on the | |
297 | command, and is one of \fBrename\fR or \fBdelete\fR as | |
298 | defined above. The trace operation cannot be used to stop a command | |
299 | from being deleted. Tcl will always remove the command once the trace | |
300 | is complete. Recursive renaming or deleting will not cause further traces | |
301 | of the same type to be evaluated, so a delete trace which itself | |
302 | deletes the command, or a rename trace which itself renames the | |
303 | command will not cause further trace evaluations to occur. | |
304 | Both \fIoldName\fR and \fInewName\fR are fully qualified with any namespace(s) | |
305 | in which they appear. | |
306 | .RE | |
307 | .TP | |
308 | \fBtrace add execution\fR \fIname ops command\fR | |
309 | Arrange for \fIcommand\fR to be executed whenever command \fIname\fR | |
310 | is executed, with traces occurring at the points indicated by the list | |
311 | \fIops\fR. \fIName\fR will be | |
312 | resolved using the usual namespace resolution rules used by | |
313 | procedures. If the command does not exist, an error will be thrown. | |
314 | .RS | |
315 | .PP | |
316 | \fIOps\fR indicates which operations are of interest, and is a list of | |
317 | one or more of the following items: | |
318 | .TP | |
319 | \fBenter\fR | |
320 | Invoke \fIcommand\fR whenever the command \fIname\fR is executed, | |
321 | just before the actual execution takes place. | |
322 | .TP | |
323 | \fBleave\fR | |
324 | Invoke \fIcommand\fR whenever the command \fIname\fR is executed, | |
325 | just after the actual execution takes place. | |
326 | .TP | |
327 | \fBenterstep\fR | |
328 | Invoke \fIcommand\fR for every Tcl command which is executed | |
329 | inside the procedure \fIname\fR, just before the actual execution | |
330 | takes place. For example if we have 'proc foo {} { puts "hello" }', | |
331 | then an \fIenterstep\fR trace would be | |
332 | invoked just before \fIputs "hello"\fR is executed. | |
333 | Setting an \fIenterstep\fR trace on a \fIcommand\fR | |
334 | will not result in an error and is simply ignored. | |
335 | .TP | |
336 | \fBleavestep\fR | |
337 | Invoke \fIcommand\fR for every Tcl command which is executed | |
338 | inside the procedure \fIname\fR, just after the actual execution | |
339 | takes place. | |
340 | Setting a \fIleavestep\fR trace on a \fIcommand\fR | |
341 | will not result in an error and is simply ignored. | |
342 | .PP | |
343 | When the trace triggers, depending on the operations being traced, a | |
344 | number of arguments are appended to \fIcommand\fR so that the actual | |
345 | command is as follows: | |
346 | .PP | |
347 | For \fBenter\fR and \fBenterstep\fR operations: | |
348 | .CS | |
349 | \fIcommand command-string op\fR | |
350 | .CE | |
351 | \fICommand-string\fR gives the complete current command being | |
352 | executed (the traced command for a \fBenter\fR operation, an | |
353 | arbitrary command for a \fBenterstep\fR operation), including | |
354 | all arguments in their fully expanded form. | |
355 | \fIOp\fR indicates what operation is being performed on the | |
356 | command execution, and is one of \fBenter\fR or \fBenterstep\fR as | |
357 | defined above. The trace operation can be used to stop the | |
358 | command from executing, by deleting the command in question. Of | |
359 | course when the command is subsequently executed, an 'invalid command' | |
360 | error will occur. | |
361 | .PP | |
362 | For \fBleave\fR and \fBleavestep\fR operations: | |
363 | .CS | |
364 | \fIcommand command-string code result op\fR | |
365 | .CE | |
366 | \fICommand-string\fR gives the complete current command being | |
367 | executed (the traced command for a \fBenter\fR operation, an | |
368 | arbitrary command for a \fBenterstep\fR operation), including | |
369 | all arguments in their fully expanded form. | |
370 | \fICode\fR gives the result code of that execution, and \fIresult\fR | |
371 | the result string. | |
372 | \fIOp\fR indicates what operation is being performed on the | |
373 | command execution, and is one of \fBleave\fR or \fBleavestep\fR as | |
374 | defined above. | |
375 | Note that the creation of many \fBenterstep\fR or | |
376 | \fBleavestep\fR traces can lead to unintuitive results, since the | |
377 | invoked commands from one trace can themselves lead to further | |
378 | command invocations for other traces. | |
379 | .PP | |
380 | \fICommand\fR executes in the same context as the code that invoked | |
381 | the traced operation: thus the \fIcommand\fR, if invoked from a procedure, | |
382 | will have access to the same local variables as code in the procedure. | |
383 | This context may be different than the context in which the trace was | |
384 | created. If \fIcommand\fR invokes a procedure (which it normally does) | |
385 | then the procedure will have to use upvar or uplevel commands if it wishes | |
386 | to access the local variables of the code which invoked the trace operation. | |
387 | .PP | |
388 | While \fIcommand\fR is executing during an execution trace, traces | |
389 | on \fIname\fR are temporarily disabled. This allows the \fIcommand\fR | |
390 | to execute \fIname\fR in its body without invoking any other traces again. | |
391 | If an error occurs while executing the \fIcommand\fR body, then the | |
392 | command \fIname\fR as a whole will return that same error. | |
393 | .PP | |
394 | When multiple traces are set on \fIname\fR, then for \fIenter\fR | |
395 | and \fIenterstep\fR operations, the traced commands are invoked | |
396 | in the reverse order of how the traces were originally created; | |
397 | and for \fIleave\fR and \fIleavestep\fR operations, the traced | |
398 | commands are invoked in the original order of creation. | |
399 | .PP | |
400 | The behavior of execution traces is currently undefined for a command | |
401 | \fIname\fR imported into another namespace. | |
402 | .RE | |
403 | .TP | |
404 | \fBtrace add variable\fI name ops command\fR | |
405 | Arrange for \fIcommand\fR to be executed whenever variable \fIname\fR | |
406 | is accessed in one of the ways given by the list \fIops\fR. \fIName\fR may | |
407 | refer to a normal variable, an element of an array, or to an array | |
408 | as a whole (i.e. \fIname\fR may be just the name of an array, with no | |
409 | parenthesized index). If \fIname\fR refers to a whole array, then | |
410 | \fIcommand\fR is invoked whenever any element of the array is | |
411 | manipulated. If the variable does not exist, it will be created but | |
412 | will not be given a value, so it will be visible to \fBnamespace which\fR | |
413 | queries, but not to \fBinfo exists\fR queries. | |
414 | .RS | |
415 | .PP | |
416 | \fIOps\fR indicates which operations are of interest, and is a list of | |
417 | one or more of the following items: | |
418 | .TP | |
419 | \fBarray\fR | |
420 | Invoke \fIcommand\fR whenever the variable is accessed or modified via | |
421 | the \fBarray\fR command, provided that \fIname\fR is not a scalar | |
422 | variable at the time that the \fBarray\fR command is invoked. If | |
423 | \fIname\fR is a scalar variable, the access via the \fBarray\fR | |
424 | command will not trigger the trace. | |
425 | .TP | |
426 | \fBread\fR | |
427 | Invoke \fIcommand\fR whenever the variable is read. | |
428 | .TP | |
429 | \fBwrite\fR | |
430 | Invoke \fIcommand\fR whenever the variable is written. | |
431 | .TP | |
432 | \fBunset\fR | |
433 | Invoke \fIcommand\fR whenever the variable is unset. Variables | |
434 | can be unset explicitly with the \fBunset\fR command, or | |
435 | implicitly when procedures return (all of their local variables | |
436 | are unset). Variables are also unset when interpreters are | |
437 | deleted, but traces will not be invoked because there is no | |
438 | interpreter in which to execute them. | |
439 | .PP | |
440 | When the trace triggers, three arguments are appended to | |
441 | \fIcommand\fR so that the actual command is as follows: | |
442 | .CS | |
443 | \fIcommand name1 name2 op\fR | |
444 | .CE | |
445 | \fIName1\fR and \fIname2\fR give the name(s) for the variable | |
446 | being accessed: if the variable is a scalar then \fIname1\fR | |
447 | gives the variable's name and \fIname2\fR is an empty string; | |
448 | if the variable is an array element then \fIname1\fR gives the | |
449 | name of the array and name2 gives the index into the array; | |
450 | if an entire array is being deleted and the trace was registered | |
451 | on the overall array, rather than a single element, then \fIname1\fR | |
452 | gives the array name and \fIname2\fR is an empty string. | |
453 | \fIName1\fR and \fIname2\fR are not necessarily the same as the | |
454 | name used in the \fBtrace variable\fR command: the \fBupvar\fR | |
455 | command allows a procedure to reference a variable under a | |
456 | different name. | |
457 | \fIOp\fR indicates what operation is being performed on the | |
458 | variable, and is one of \fBread\fR, \fBwrite\fR, or \fBunset\fR as | |
459 | defined above. | |
460 | .PP | |
461 | \fICommand\fR executes in the same context as the code that invoked | |
462 | the traced operation: if the variable was accessed as part of a Tcl | |
463 | procedure, then \fIcommand\fR will have access to the same local | |
464 | variables as code in the procedure. This context may be different | |
465 | than the context in which the trace was created. If \fIcommand\fR | |
466 | invokes a procedure (which it normally does) then the procedure will | |
467 | have to use \fBupvar\fR or \fBuplevel\fR if it wishes to access the | |
468 | traced variable. Note also that \fIname1\fR may not necessarily be | |
469 | the same as the name used to set the trace on the variable; | |
470 | differences can occur if the access is made through a variable defined | |
471 | with the \fBupvar\fR command. | |
472 | .PP | |
473 | For read and write traces, \fIcommand\fR can modify the variable to | |
474 | affect the result of the traced operation. If \fIcommand\fR modifies | |
475 | the value of a variable during a read or write trace, then the new | |
476 | value will be returned as the result of the traced operation. The | |
477 | return value from \fIcommand\fR is ignored except that if it returns | |
478 | an error of any sort then the traced operation also returns an error | |
479 | with the same error message returned by the trace command (this | |
480 | mechanism can be used to implement read-only variables, for example). | |
481 | For write traces, \fIcommand\fR is invoked after the variable's value | |
482 | has been changed; it can write a new value into the variable to | |
483 | override the original value specified in the write operation. To | |
484 | implement read-only variables, \fIcommand\fR will have to restore the | |
485 | old value of the variable. | |
486 | .PP | |
487 | While \fIcommand\fR is executing during a read or write trace, traces | |
488 | on the variable are temporarily disabled. This means that reads and | |
489 | writes invoked by \fIcommand\fR will occur directly, without invoking | |
490 | \fIcommand\fR (or any other traces) again. However, if \fIcommand\fR | |
491 | unsets the variable then unset traces will be invoked. | |
492 | .PP | |
493 | When an unset trace is invoked, the variable has already been deleted: | |
494 | it will appear to be undefined with no traces. If an unset occurs | |
495 | because of a procedure return, then the trace will be invoked in the | |
496 | variable context of the procedure being returned to: the stack frame | |
497 | of the returning procedure will no longer exist. Traces are not | |
498 | disabled during unset traces, so if an unset trace command creates a | |
499 | new trace and accesses the variable, the trace will be invoked. Any | |
500 | errors in unset traces are ignored. | |
501 | .PP | |
502 | If there are multiple traces on a variable they are invoked in order | |
503 | of creation, most-recent first. If one trace returns an error, then | |
504 | no further traces are invoked for the variable. If an array element | |
505 | has a trace set, and there is also a trace set on the array as a | |
506 | whole, the trace on the overall array is invoked before the one on the | |
507 | element. | |
508 | .PP | |
509 | Once created, the trace remains in effect either until the trace is | |
510 | removed with the \fBtrace remove variable\fR command described below, | |
511 | until the variable is unset, or until the interpreter is deleted. | |
512 | Unsetting an element of array will remove any traces on that element, | |
513 | but will not remove traces on the overall array. | |
514 | .PP | |
515 | This command returns an empty string. | |
516 | .RE | |
517 | .RE | |
518 | .TP | |
519 | \fBtrace remove \fItype name opList command\fR | |
520 | Where \fItype\fR is either \fBcommand\fR, \fBexecution\fR or \fBvariable\fR. | |
521 | .RS | |
522 | .TP | |
523 | \fBtrace remove command\fI name opList command\fR | |
524 | If there is a trace set on command \fIname\fR with the operations and | |
525 | command given by \fIopList\fR and \fIcommand\fR, then the trace is | |
526 | removed, so that \fIcommand\fR will never again be invoked. Returns | |
527 | an empty string. If \fIname\fR doesn't exist, the command will throw | |
528 | an error. | |
529 | .TP | |
530 | \fBtrace remove execution\fI name opList command\fR | |
531 | If there is a trace set on command \fIname\fR with the operations and | |
532 | command given by \fIopList\fR and \fIcommand\fR, then the trace is | |
533 | removed, so that \fIcommand\fR will never again be invoked. Returns | |
534 | an empty string. If \fIname\fR doesn't exist, the command will throw | |
535 | an error. | |
536 | .TP | |
537 | \fBtrace remove variable\fI name opList command\fR | |
538 | If there is a trace set on variable \fIname\fR with the operations and | |
539 | command given by \fIopList\fR and \fIcommand\fR, then the trace is | |
540 | removed, so that \fIcommand\fR will never again be invoked. Returns | |
541 | an empty string. | |
542 | .RE | |
543 | .TP | |
544 | \fBtrace info \fItype name\fR | |
545 | Where \fItype\fR is either \fBcommand\fR, \fBexecution\fR or \fBvariable\fR. | |
546 | .RS | |
547 | .TP | |
548 | \fBtrace info command\fI name\fR | |
549 | Returns a list containing one element for each trace currently set on | |
550 | command \fIname\fR. Each element of the list is itself a list | |
551 | containing two elements, which are the \fIopList\fR and \fIcommand\fR | |
552 | associated with the trace. If \fIname\fR doesn't have any traces set, | |
553 | then the result of the command will be an empty string. If \fIname\fR | |
554 | doesn't exist, the command will throw an error. | |
555 | .TP | |
556 | \fBtrace info execution\fI name\fR | |
557 | Returns a list containing one element for each trace currently set on | |
558 | command \fIname\fR. Each element of the list is itself a list | |
559 | containing two elements, which are the \fIopList\fR and \fIcommand\fR | |
560 | associated with the trace. If \fIname\fR doesn't have any traces set, | |
561 | then the result of the command will be an empty string. If \fIname\fR | |
562 | doesn't exist, the command will throw an error. | |
563 | .TP | |
564 | \fBtrace info variable\fI name\fR | |
565 | Returns a list containing one element for each trace currently set on | |
566 | variable \fIname\fR. Each element of the list is itself a list | |
567 | containing two elements, which are the \fIopList\fR and \fIcommand\fR | |
568 | associated with the trace. If \fIname\fR doesn't exist or doesn't | |
569 | have any traces set, then the result of the command will be an empty | |
570 | string. | |
571 | .RE | |
572 | .PP | |
573 | For backwards compatibility, three other subcommands are available: | |
574 | .RS | |
575 | .TP | |
576 | \fBtrace variable \fIname ops command\fR | |
577 | This is equivalent to \fBtrace add variable \fIname ops command\fR. | |
578 | .TP | |
579 | \fBtrace vdelete \fIname ops command\fR | |
580 | This is equivalent to \fBtrace remove variable \fIname ops command\fR | |
581 | .TP | |
582 | \fBtrace vinfo \fIname\fR | |
583 | This is equivalent to \fBtrace info variable \fIname\fR | |
584 | .RE | |
585 | .PP | |
586 | These subcommands are deprecated and will likely be removed in a | |
587 | future version of Tcl. They use an older syntax in which \fBarray\fR, | |
588 | \fBread\fR, \fBwrite\fR, \fBunset\fR are replaced by \fBa\fR, \fBr\fR, | |
589 | \fBw\fR and \fBu\fR respectively, and the \fIops\fR argument is not a | |
590 | list, but simply a string concatenation of the operations, such as | |
591 | \fBrwua\fR. | |
592 | .SH EXAMPLES | |
593 | Print a message whenever either of the global variables \fBfoo\fR and | |
594 | \fBbar\fR are updated, even if they have a different local name at the | |
595 | time (which can be done with the \fBupvar\fR command): | |
596 | .CS | |
597 | proc tracer {varname args} { | |
598 | upvar #0 $varname var | |
599 | puts "$varname was updated to be \e"$var\e"" | |
600 | } | |
601 | \fBtrace add\fR variable foo write "tracer foo" | |
602 | \fBtrace add\fR variable bar write "tracer bar" | |
603 | .CE | |
604 | .PP | |
605 | Ensure that the global variable \fBfoobar\fR always contains the | |
606 | product of the global variables \fBfoo\fR and \fBbar\fR: | |
607 | .CS | |
608 | proc doMult args { | |
609 | global foo bar foobar | |
610 | set foobar [expr {$foo * $bar}] | |
611 | } | |
612 | \fBtrace add\fR variable foo write doMult | |
613 | \fBtrace add\fR variable bar write doMult | |
614 | .CE | |
615 | ||
616 | .SH "SEE ALSO" | |
617 | set(n), unset(n) | |
618 | ||
619 | .SH KEYWORDS | |
620 | read, command, rename, variable, write, trace, unset |