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1 | '\" |
2 | '\" Copyright (c) 1993 The Regents of the University of California. | |
3 | '\" Copyright (c) 1994-1997 Sun Microsystems, Inc. | |
4 | '\" | |
5 | '\" See the file "license.terms" for information on usage and redistribution | |
6 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. | |
7 | '\" | |
8 | '\" RCS: @(#) $Id: upvar.n,v 1.5.18.2 2004/11/12 09:02:30 das Exp $ | |
9 | '\" | |
10 | '\" The definitions below are for supplemental macros used in Tcl/Tk | |
11 | '\" manual entries. | |
12 | '\" | |
13 | '\" .AP type name in/out ?indent? | |
14 | '\" Start paragraph describing an argument to a library procedure. | |
15 | '\" type is type of argument (int, etc.), in/out is either "in", "out", | |
16 | '\" or "in/out" to describe whether procedure reads or modifies arg, | |
17 | '\" and indent is equivalent to second arg of .IP (shouldn't ever be | |
18 | '\" needed; use .AS below instead) | |
19 | '\" | |
20 | '\" .AS ?type? ?name? | |
21 | '\" Give maximum sizes of arguments for setting tab stops. Type and | |
22 | '\" name are examples of largest possible arguments that will be passed | |
23 | '\" to .AP later. If args are omitted, default tab stops are used. | |
24 | '\" | |
25 | '\" .BS | |
26 | '\" Start box enclosure. From here until next .BE, everything will be | |
27 | '\" enclosed in one large box. | |
28 | '\" | |
29 | '\" .BE | |
30 | '\" End of box enclosure. | |
31 | '\" | |
32 | '\" .CS | |
33 | '\" Begin code excerpt. | |
34 | '\" | |
35 | '\" .CE | |
36 | '\" End code excerpt. | |
37 | '\" | |
38 | '\" .VS ?version? ?br? | |
39 | '\" Begin vertical sidebar, for use in marking newly-changed parts | |
40 | '\" of man pages. The first argument is ignored and used for recording | |
41 | '\" the version when the .VS was added, so that the sidebars can be | |
42 | '\" found and removed when they reach a certain age. If another argument | |
43 | '\" is present, then a line break is forced before starting the sidebar. | |
44 | '\" | |
45 | '\" .VE | |
46 | '\" End of vertical sidebar. | |
47 | '\" | |
48 | '\" .DS | |
49 | '\" Begin an indented unfilled display. | |
50 | '\" | |
51 | '\" .DE | |
52 | '\" End of indented unfilled display. | |
53 | '\" | |
54 | '\" .SO | |
55 | '\" Start of list of standard options for a Tk widget. The | |
56 | '\" options follow on successive lines, in four columns separated | |
57 | '\" by tabs. | |
58 | '\" | |
59 | '\" .SE | |
60 | '\" End of list of standard options for a Tk widget. | |
61 | '\" | |
62 | '\" .OP cmdName dbName dbClass | |
63 | '\" Start of description of a specific option. cmdName gives the | |
64 | '\" option's name as specified in the class command, dbName gives | |
65 | '\" the option's name in the option database, and dbClass gives | |
66 | '\" the option's class in the option database. | |
67 | '\" | |
68 | '\" .UL arg1 arg2 | |
69 | '\" Print arg1 underlined, then print arg2 normally. | |
70 | '\" | |
71 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ | |
72 | '\" | |
73 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. | |
74 | .if t .wh -1.3i ^B | |
75 | .nr ^l \n(.l | |
76 | .ad b | |
77 | '\" # Start an argument description | |
78 | .de AP | |
79 | .ie !"\\$4"" .TP \\$4 | |
80 | .el \{\ | |
81 | . ie !"\\$2"" .TP \\n()Cu | |
82 | . el .TP 15 | |
83 | .\} | |
84 | .ta \\n()Au \\n()Bu | |
85 | .ie !"\\$3"" \{\ | |
86 | \&\\$1 \\fI\\$2\\fP (\\$3) | |
87 | .\".b | |
88 | .\} | |
89 | .el \{\ | |
90 | .br | |
91 | .ie !"\\$2"" \{\ | |
92 | \&\\$1 \\fI\\$2\\fP | |
93 | .\} | |
94 | .el \{\ | |
95 | \&\\fI\\$1\\fP | |
96 | .\} | |
97 | .\} | |
98 | .. | |
99 | '\" # define tabbing values for .AP | |
100 | .de AS | |
101 | .nr )A 10n | |
102 | .if !"\\$1"" .nr )A \\w'\\$1'u+3n | |
103 | .nr )B \\n()Au+15n | |
104 | .\" | |
105 | .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n | |
106 | .nr )C \\n()Bu+\\w'(in/out)'u+2n | |
107 | .. | |
108 | .AS Tcl_Interp Tcl_CreateInterp in/out | |
109 | '\" # BS - start boxed text | |
110 | '\" # ^y = starting y location | |
111 | '\" # ^b = 1 | |
112 | .de BS | |
113 | .br | |
114 | .mk ^y | |
115 | .nr ^b 1u | |
116 | .if n .nf | |
117 | .if n .ti 0 | |
118 | .if n \l'\\n(.lu\(ul' | |
119 | .if n .fi | |
120 | .. | |
121 | '\" # BE - end boxed text (draw box now) | |
122 | .de BE | |
123 | .nf | |
124 | .ti 0 | |
125 | .mk ^t | |
126 | .ie n \l'\\n(^lu\(ul' | |
127 | .el \{\ | |
128 | .\" Draw four-sided box normally, but don't draw top of | |
129 | .\" box if the box started on an earlier page. | |
130 | .ie !\\n(^b-1 \{\ | |
131 | \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' | |
132 | .\} | |
133 | .el \}\ | |
134 | \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' | |
135 | .\} | |
136 | .\} | |
137 | .fi | |
138 | .br | |
139 | .nr ^b 0 | |
140 | .. | |
141 | '\" # VS - start vertical sidebar | |
142 | '\" # ^Y = starting y location | |
143 | '\" # ^v = 1 (for troff; for nroff this doesn't matter) | |
144 | .de VS | |
145 | .if !"\\$2"" .br | |
146 | .mk ^Y | |
147 | .ie n 'mc \s12\(br\s0 | |
148 | .el .nr ^v 1u | |
149 | .. | |
150 | '\" # VE - end of vertical sidebar | |
151 | .de VE | |
152 | .ie n 'mc | |
153 | .el \{\ | |
154 | .ev 2 | |
155 | .nf | |
156 | .ti 0 | |
157 | .mk ^t | |
158 | \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' | |
159 | .sp -1 | |
160 | .fi | |
161 | .ev | |
162 | .\} | |
163 | .nr ^v 0 | |
164 | .. | |
165 | '\" # Special macro to handle page bottom: finish off current | |
166 | '\" # box/sidebar if in box/sidebar mode, then invoked standard | |
167 | '\" # page bottom macro. | |
168 | .de ^B | |
169 | .ev 2 | |
170 | 'ti 0 | |
171 | 'nf | |
172 | .mk ^t | |
173 | .if \\n(^b \{\ | |
174 | .\" Draw three-sided box if this is the box's first page, | |
175 | .\" draw two sides but no top otherwise. | |
176 | .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 | |
177 | .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c | |
178 | .\} | |
179 | .if \\n(^v \{\ | |
180 | .nr ^x \\n(^tu+1v-\\n(^Yu | |
181 | \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c | |
182 | .\} | |
183 | .bp | |
184 | 'fi | |
185 | .ev | |
186 | .if \\n(^b \{\ | |
187 | .mk ^y | |
188 | .nr ^b 2 | |
189 | .\} | |
190 | .if \\n(^v \{\ | |
191 | .mk ^Y | |
192 | .\} | |
193 | .. | |
194 | '\" # DS - begin display | |
195 | .de DS | |
196 | .RS | |
197 | .nf | |
198 | .sp | |
199 | .. | |
200 | '\" # DE - end display | |
201 | .de DE | |
202 | .fi | |
203 | .RE | |
204 | .sp | |
205 | .. | |
206 | '\" # SO - start of list of standard options | |
207 | .de SO | |
208 | .SH "STANDARD OPTIONS" | |
209 | .LP | |
210 | .nf | |
211 | .ta 5.5c 11c | |
212 | .ft B | |
213 | .. | |
214 | '\" # SE - end of list of standard options | |
215 | .de SE | |
216 | .fi | |
217 | .ft R | |
218 | .LP | |
219 | See the \\fBoptions\\fR manual entry for details on the standard options. | |
220 | .. | |
221 | '\" # OP - start of full description for a single option | |
222 | .de OP | |
223 | .LP | |
224 | .nf | |
225 | .ta 4c | |
226 | Command-Line Name: \\fB\\$1\\fR | |
227 | Database Name: \\fB\\$2\\fR | |
228 | Database Class: \\fB\\$3\\fR | |
229 | .fi | |
230 | .IP | |
231 | .. | |
232 | '\" # CS - begin code excerpt | |
233 | .de CS | |
234 | .RS | |
235 | .nf | |
236 | .ta .25i .5i .75i 1i | |
237 | .. | |
238 | '\" # CE - end code excerpt | |
239 | .de CE | |
240 | .fi | |
241 | .RE | |
242 | .. | |
243 | .de UL | |
244 | \\$1\l'|0\(ul'\\$2 | |
245 | .. | |
246 | .TH upvar n "" Tcl "Tcl Built-In Commands" | |
247 | .BS | |
248 | '\" Note: do not modify the .SH NAME line immediately below! | |
249 | .SH NAME | |
250 | upvar \- Create link to variable in a different stack frame | |
251 | .SH SYNOPSIS | |
252 | \fBupvar \fR?\fIlevel\fR? \fIotherVar myVar \fR?\fIotherVar myVar \fR...? | |
253 | .BE | |
254 | ||
255 | .SH DESCRIPTION | |
256 | .PP | |
257 | This command arranges for one or more local variables in the current | |
258 | procedure to refer to variables in an enclosing procedure call or | |
259 | to global variables. | |
260 | \fILevel\fR may have any of the forms permitted for the \fBuplevel\fR | |
261 | command, and may be omitted if the first letter of the first \fIotherVar\fR | |
262 | isn't \fB#\fR or a digit (it defaults to \fB1\fR). | |
263 | For each \fIotherVar\fR argument, \fBupvar\fR makes the variable | |
264 | by that name in the procedure frame given by \fIlevel\fR (or at | |
265 | global level, if \fIlevel\fR is \fB#0\fR) accessible | |
266 | in the current procedure by the name given in the corresponding | |
267 | \fImyVar\fR argument. | |
268 | The variable named by \fIotherVar\fR need not exist at the time of the | |
269 | call; it will be created the first time \fImyVar\fR is referenced, just like | |
270 | an ordinary variable. There must not exist a variable by the | |
271 | name \fImyVar\fR at the time \fBupvar\fR is invoked. | |
272 | \fIMyVar\fR is always treated as the name of a variable, not an | |
273 | array element. Even if the name looks like an array element, | |
274 | such as \fBa(b)\fR, a regular variable is created. | |
275 | \fIOtherVar\fR may refer to a scalar variable, an array, | |
276 | or an array element. | |
277 | \fBUpvar\fR returns an empty string. | |
278 | .PP | |
279 | The \fBupvar\fR command simplifies the implementation of call-by-name | |
280 | procedure calling and also makes it easier to build new control constructs | |
281 | as Tcl procedures. | |
282 | For example, consider the following procedure: | |
283 | .CS | |
284 | proc add2 name { | |
285 | \fBupvar\fR $name x | |
286 | set x [expr $x+2] | |
287 | } | |
288 | .CE | |
289 | \fBadd2\fR is invoked with an argument giving the name of a variable, | |
290 | and it adds two to the value of that variable. | |
291 | Although \fBadd2\fR could have been implemented using \fBuplevel\fR | |
292 | instead of \fBupvar\fR, \fBupvar\fR makes it simpler for \fBadd2\fR | |
293 | to access the variable in the caller's procedure frame. | |
294 | .PP | |
295 | \fBnamespace eval\fR is another way (besides procedure calls) | |
296 | that the Tcl naming context can change. | |
297 | It adds a call frame to the stack to represent the namespace context. | |
298 | This means each \fBnamespace eval\fR command | |
299 | counts as another call level for \fBuplevel\fR and \fBupvar\fR commands. | |
300 | For example, \fBinfo level 1\fR will return a list | |
301 | describing a command that is either | |
302 | the outermost procedure call or the outermost \fBnamespace eval\fR command. | |
303 | Also, \fBuplevel #0\fR evaluates a script | |
304 | at top-level in the outermost namespace (the global namespace). | |
305 | .PP | |
306 | .VS | |
307 | If an upvar variable is unset (e.g. \fBx\fR in \fBadd2\fR above), the | |
308 | \fBunset\fR operation affects the variable it is linked to, not the | |
309 | upvar variable. There is no way to unset an upvar variable except | |
310 | by exiting the procedure in which it is defined. However, it is | |
311 | possible to retarget an upvar variable by executing another \fBupvar\fR | |
312 | command. | |
313 | .SH "TRACES AND UPVAR" | |
314 | .PP | |
315 | Upvar interacts with traces in a straightforward but possibly | |
316 | unexpected manner. If a variable trace is defined on \fIotherVar\fR, that | |
317 | trace will be triggered by actions involving \fImyVar\fR. However, | |
318 | the trace procedure will be passed the name of \fImyVar\fR, rather | |
319 | than the name of \fIotherVar\fR. Thus, the output of the following code | |
320 | will be \fBlocalVar\fR rather than \fBoriginalVar\fR: | |
321 | .CS | |
322 | proc \fBtraceproc\fR { name index op } { | |
323 | puts $name | |
324 | } | |
325 | proc \fBsetByUpvar\fR { name value } { | |
326 | \fBupvar\fR $name localVar | |
327 | set localVar $value | |
328 | } | |
329 | set originalVar 1 | |
330 | trace variable originalVar w \fBtraceproc\fR | |
331 | \fBsetByUpvar\fR originalVar 2 | |
332 | } | |
333 | .CE | |
334 | .PP | |
335 | If \fIotherVar\fR refers to an element of an array, then variable | |
336 | traces set for the entire array will not be invoked when \fImyVar\fR | |
337 | is accessed (but traces on the particular element will still be | |
338 | invoked). In particular, if the array is \fBenv\fR, then changes | |
339 | made to \fImyVar\fR will not be passed to subprocesses correctly. | |
340 | .VE | |
341 | .SH EXAMPLE | |
342 | A \fBdecr\fR command that works like \fBincr\fR except it subtracts | |
343 | the value from the variable instead of adding it: | |
344 | .CS | |
345 | proc decr {varName {decrement 1}} { | |
346 | \fBupvar\fR 1 $varName var | |
347 | incr var [expr {-$decrement}] | |
348 | } | |
349 | .CE | |
350 | ||
351 | .SH "SEE ALSO" | |
352 | global(n), namespace(n), uplevel(n), variable(n) | |
353 | ||
354 | .SH KEYWORDS | |
355 | context, frame, global, level, namespace, procedure, variable |