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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 | '\" | |
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: exec.n,v 1.6.2.1 2004/10/27 09:35:38 dkf 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 exec n 7.6 Tcl "Tcl Built-In Commands" | |
247 | .BS | |
248 | '\" Note: do not modify the .SH NAME line immediately below! | |
249 | .SH NAME | |
250 | exec \- Invoke subprocesses | |
251 | .SH SYNOPSIS | |
252 | \fBexec \fR?\fIswitches\fR? \fIarg \fR?\fIarg ...\fR? | |
253 | .BE | |
254 | ||
255 | .SH DESCRIPTION | |
256 | .PP | |
257 | This command treats its arguments as the specification | |
258 | of one or more subprocesses to execute. | |
259 | The arguments take the form of a standard shell pipeline | |
260 | where each \fIarg\fR becomes one word of a command, and | |
261 | each distinct command becomes a subprocess. | |
262 | .PP | |
263 | If the initial arguments to \fBexec\fR start with \fB\-\fR then | |
264 | they are treated as command-line switches and are not part | |
265 | of the pipeline specification. The following switches are | |
266 | currently supported: | |
267 | .TP 13 | |
268 | \fB\-keepnewline\fR | |
269 | Retains a trailing newline in the pipeline's output. | |
270 | Normally a trailing newline will be deleted. | |
271 | .TP 13 | |
272 | \fB\-\|\-\fR | |
273 | Marks the end of switches. The argument following this one will | |
274 | be treated as the first \fIarg\fR even if it starts with a \fB\-\fR. | |
275 | .PP | |
276 | If an \fIarg\fR (or pair of \fIarg\fRs) has one of the forms | |
277 | described below then it is used by \fBexec\fR to control the | |
278 | flow of input and output among the subprocess(es). | |
279 | Such arguments will not be passed to the subprocess(es). In forms | |
280 | such as ``< \fIfileName\fR'' \fIfileName\fR may either be in a | |
281 | separate argument from ``<'' or in the same argument with no | |
282 | intervening space (i.e. ``<\fIfileName\fR''). | |
283 | .TP 15 | |
284 | | | |
285 | Separates distinct commands in the pipeline. The standard output | |
286 | of the preceding command will be piped into the standard input | |
287 | of the next command. | |
288 | .TP 15 | |
289 | |& | |
290 | Separates distinct commands in the pipeline. Both standard output | |
291 | and standard error of the preceding command will be piped into | |
292 | the standard input of the next command. | |
293 | This form of redirection overrides forms such as 2> and >&. | |
294 | .TP 15 | |
295 | <\0\fIfileName\fR | |
296 | The file named by \fIfileName\fR is opened and used as the standard | |
297 | input for the first command in the pipeline. | |
298 | .TP 15 | |
299 | <@\0\fIfileId\fR | |
300 | \fIFileId\fR must be the identifier for an open file, such as the return | |
301 | value from a previous call to \fBopen\fR. | |
302 | It is used as the standard input for the first command in the pipeline. | |
303 | \fIFileId\fR must have been opened for reading. | |
304 | .TP 15 | |
305 | <<\0\fIvalue\fR | |
306 | \fIValue\fR is passed to the first command as its standard input. | |
307 | .TP 15 | |
308 | >\0\fIfileName\fR | |
309 | Standard output from the last command is redirected to the file named | |
310 | \fIfileName\fR, overwriting its previous contents. | |
311 | .TP 15 | |
312 | 2>\0\fIfileName\fR | |
313 | Standard error from all commands in the pipeline is redirected to the | |
314 | file named \fIfileName\fR, overwriting its previous contents. | |
315 | .TP 15 | |
316 | >&\0\fIfileName\fR | |
317 | Both standard output from the last command and standard error from all | |
318 | commands are redirected to the file named \fIfileName\fR, overwriting | |
319 | its previous contents. | |
320 | .TP 15 | |
321 | >>\0\fIfileName\fR | |
322 | Standard output from the last command is | |
323 | redirected to the file named \fIfileName\fR, appending to it rather | |
324 | than overwriting it. | |
325 | .TP 15 | |
326 | 2>>\0\fIfileName\fR | |
327 | Standard error from all commands in the pipeline is | |
328 | redirected to the file named \fIfileName\fR, appending to it rather | |
329 | than overwriting it. | |
330 | .TP 15 | |
331 | >>&\0\fIfileName\fR | |
332 | Both standard output from the last command and standard error from | |
333 | all commands are redirected to the file named \fIfileName\fR, | |
334 | appending to it rather than overwriting it. | |
335 | .TP 15 | |
336 | >@\0\fIfileId\fR | |
337 | \fIFileId\fR must be the identifier for an open file, such as the return | |
338 | value from a previous call to \fBopen\fR. | |
339 | Standard output from the last command is redirected to \fIfileId\fR's | |
340 | file, which must have been opened for writing. | |
341 | .TP 15 | |
342 | 2>@\0\fIfileId\fR | |
343 | \fIFileId\fR must be the identifier for an open file, such as the return | |
344 | value from a previous call to \fBopen\fR. | |
345 | Standard error from all commands in the pipeline is | |
346 | redirected to \fIfileId\fR's file. | |
347 | The file must have been opened for writing. | |
348 | .TP 15 | |
349 | >&@\0\fIfileId\fR | |
350 | \fIFileId\fR must be the identifier for an open file, such as the return | |
351 | value from a previous call to \fBopen\fR. | |
352 | Both standard output from the last command and standard error from | |
353 | all commands are redirected to \fIfileId\fR's file. | |
354 | The file must have been opened for writing. | |
355 | .PP | |
356 | If standard output has not been redirected then the \fBexec\fR | |
357 | command returns the standard output from the last command | |
358 | in the pipeline. | |
359 | If any of the commands in the pipeline exit abnormally or | |
360 | are killed or suspended, then \fBexec\fR will return an error | |
361 | and the error message will include the pipeline's output followed by | |
362 | error messages describing the abnormal terminations; the | |
363 | \fBerrorCode\fR variable will contain additional information | |
364 | about the last abnormal termination encountered. | |
365 | If any of the commands writes to its standard error file and that | |
366 | standard error isn't redirected, | |
367 | then \fBexec\fR will return an error; the error message | |
368 | will include the pipeline's standard output, followed by messages | |
369 | about abnormal terminations (if any), followed by the standard error | |
370 | output. | |
371 | .PP | |
372 | If the last character of the result or error message | |
373 | is a newline then that character is normally deleted | |
374 | from the result or error message. | |
375 | This is consistent with other Tcl return values, which don't | |
376 | normally end with newlines. | |
377 | However, if \fB\-keepnewline\fR is specified then the trailing | |
378 | newline is retained. | |
379 | .PP | |
380 | If standard input isn't redirected with ``<'' or ``<<'' | |
381 | or ``<@'' then the standard input for the first command in the | |
382 | pipeline is taken from the application's current standard input. | |
383 | .PP | |
384 | If the last \fIarg\fR is ``&'' then the pipeline will be | |
385 | executed in background. | |
386 | In this case the \fBexec\fR command will return a list whose | |
387 | elements are the process identifiers for all of the subprocesses | |
388 | in the pipeline. | |
389 | The standard output from the last command in the pipeline will | |
390 | go to the application's standard output if it hasn't been | |
391 | redirected, and error output from all of | |
392 | the commands in the pipeline will go to the application's | |
393 | standard error file unless redirected. | |
394 | .PP | |
395 | The first word in each command is taken as the command name; | |
396 | tilde-substitution is performed on it, and if the result contains | |
397 | no slashes then the directories | |
398 | in the PATH environment variable are searched for | |
399 | an executable by the given name. | |
400 | If the name contains a slash then it must refer to an executable | |
401 | reachable from the current directory. | |
402 | No ``glob'' expansion or other shell-like substitutions | |
403 | are performed on the arguments to commands. | |
404 | ||
405 | .VS | |
406 | .SH "PORTABILITY ISSUES" | |
407 | .TP | |
408 | \fBWindows\fR (all versions) | |
409 | . | |
410 | Reading from or writing to a socket, using the ``\fB@\0\fIfileId\fR'' | |
411 | notation, does not work. When reading from a socket, a 16-bit DOS | |
412 | application will hang and a 32-bit application will return immediately with | |
413 | end-of-file. When either type of application writes to a socket, the | |
414 | information is instead sent to the console, if one is present, or is | |
415 | discarded. | |
416 | .sp | |
417 | The Tk console text widget does not provide real standard IO capabilities. | |
418 | Under Tk, when redirecting from standard input, all applications will see an | |
419 | immediate end-of-file; information redirected to standard output or standard | |
420 | error will be discarded. | |
421 | .sp | |
422 | Either forward or backward slashes are accepted as path separators for | |
423 | arguments to Tcl commands. When executing an application, the path name | |
424 | specified for the application may also contain forward or backward slashes | |
425 | as path separators. Bear in mind, however, that most Windows applications | |
426 | accept arguments with forward slashes only as option delimiters and | |
427 | backslashes only in paths. Any arguments to an application that specify a | |
428 | path name with forward slashes will not automatically be converted to use | |
429 | the backslash character. If an argument contains forward slashes as the | |
430 | path separator, it may or may not be recognized as a path name, depending on | |
431 | the program. | |
432 | .sp | |
433 | Additionally, when calling a 16-bit DOS or Windows 3.X application, all path | |
434 | names must use the short, cryptic, path format (e.g., using ``applba~1.def'' | |
435 | instead of ``applbakery.default''), which can be obtained with the | |
436 | \fBfile attributes $fileName -shortname\fR command. | |
437 | .sp | |
438 | Two or more forward or backward slashes in a row in a path refer to a | |
439 | network path. For example, a simple concatenation of the root directory | |
440 | \fBc:/\fR with a subdirectory \fB/windows/system\fR will yield | |
441 | \fBc://windows/system\fR (two slashes together), which refers to the mount | |
442 | point called \fBsystem\fR on the machine called \fBwindows\fR (and the | |
443 | \fBc:/\fR is ignored), and is not equivalent to \fBc:/windows/system\fR, | |
444 | which describes a directory on the current computer. The \fBfile join\fR | |
445 | command should be used to concatenate path components. | |
446 | .sp | |
447 | .RS | |
448 | Note that there are two general types of Win32 console applications: | |
449 | .RS | |
450 | 1) CLI -- CommandLine Interface, simple stdio exchange. \fBnetstat.exe\fR for | |
451 | example. | |
452 | .br | |
453 | 2) TUI -- Textmode User Interface, any application that accesses the console | |
454 | API for doing such things as cursor movement, setting text color, detecting | |
455 | key presses and mouse movement, etc. An example would be \fBtelnet.exe\fR | |
456 | from Windows 2000. These types of applications are not common in a windows | |
457 | environment, but do exist. | |
458 | .RE | |
459 | \fBexec\fR will not work well with TUI applications when a console is not | |
460 | present, as is done when launching applications under wish. It is desirable | |
461 | to have console applications hidden and detached. This is a designed-in | |
462 | limitation as \fBexec\fR wants to communicate over pipes. The Expect | |
463 | extension addresses this issue when communicating with a TUI application. | |
464 | .sp | |
465 | .RE | |
466 | .TP | |
467 | \fBWindows NT\fR | |
468 | . | |
469 | When attempting to execute an application, \fBexec\fR first searches for | |
470 | the name as it was specified. Then, in order, \fB.com\fR, \fB.exe\fR, and | |
471 | \fB.bat\fR are appended to the end of the specified name and it searches | |
472 | for the longer name. If a directory name was not specified as part of the | |
473 | application name, the following directories are automatically searched in | |
474 | order when attempting to locate the application: | |
475 | .sp | |
476 | .RS | |
477 | .RS | |
478 | The directory from which the Tcl executable was loaded. | |
479 | .br | |
480 | The current directory. | |
481 | .br | |
482 | The Windows NT 32-bit system directory. | |
483 | .br | |
484 | The Windows NT 16-bit system directory. | |
485 | .br | |
486 | The Windows NT home directory. | |
487 | .br | |
488 | The directories listed in the path. | |
489 | .RE | |
490 | .sp | |
491 | In order to execute shell built-in commands like \fBdir\fR and \fBcopy\fR, | |
492 | the caller must prepend the desired command with ``\fBcmd.exe /c\0\fR'' | |
493 | because built-in commands are not implemented using executables. | |
494 | .sp | |
495 | .RE | |
496 | .TP | |
497 | \fBWindows 9x\fR | |
498 | . | |
499 | When attempting to execute an application, \fBexec\fR first searches for | |
500 | the name as it was specified. Then, in order, \fB.com\fR, \fB.exe\fR, and | |
501 | \fB.bat\fR are appended to the end of the specified name and it searches | |
502 | for the longer name. If a directory name was not specified as part of the | |
503 | application name, the following directories are automatically searched in | |
504 | order when attempting to locate the application: | |
505 | .sp | |
506 | .RS | |
507 | .RS | |
508 | The directory from which the Tcl executable was loaded. | |
509 | .br | |
510 | The current directory. | |
511 | .br | |
512 | The Windows 9x system directory. | |
513 | .br | |
514 | The Windows 9x home directory. | |
515 | .br | |
516 | The directories listed in the path. | |
517 | .RE | |
518 | .sp | |
519 | In order to execute shell built-in commands like \fBdir\fR and \fBcopy\fR, | |
520 | the caller must prepend the desired command with ``\fBcommand.com /c\0\fR'' | |
521 | because built-in commands are not implemented using executables. | |
522 | .sp | |
523 | Once a 16-bit DOS application has read standard input from a console and | |
524 | then quit, all subsequently run 16-bit DOS applications will see the | |
525 | standard input as already closed. 32-bit applications do not have this | |
526 | problem and will run correctly, even after a 16-bit DOS application thinks | |
527 | that standard input is closed. There is no known workaround for this bug | |
528 | at this time. | |
529 | .sp | |
530 | Redirection between the \fBNUL:\fR device and a 16-bit application does not | |
531 | always work. When redirecting from \fBNUL:\fR, some applications may hang, | |
532 | others will get an infinite stream of ``0x01'' bytes, and some will actually | |
533 | correctly get an immediate end-of-file; the behavior seems to depend upon | |
534 | something compiled into the application itself. When redirecting greater than | |
535 | 4K or so to \fBNUL:\fR, some applications will hang. The above problems do not | |
536 | happen with 32-bit applications. | |
537 | .sp | |
538 | All DOS 16-bit applications are run synchronously. All standard input from | |
539 | a pipe to a 16-bit DOS application is collected into a temporary file; the | |
540 | other end of the pipe must be closed before the 16-bit DOS application | |
541 | begins executing. All standard output or error from a 16-bit DOS | |
542 | application to a pipe is collected into temporary files; the application | |
543 | must terminate before the temporary files are redirected to the next stage | |
544 | of the pipeline. This is due to a workaround for a Windows 95 bug in the | |
545 | implementation of pipes, and is how the standard Windows 95 DOS shell | |
546 | handles pipes itself. | |
547 | .sp | |
548 | Certain applications, such as \fBcommand.com\fR, should not be executed | |
549 | interactively. Applications which directly access the console window, | |
550 | rather than reading from their standard input and writing to their standard | |
551 | output may fail, hang Tcl, or even hang the system if their own private | |
552 | console window is not available to them. | |
553 | .RE | |
554 | .TP | |
555 | \fBMacintosh\fR | |
556 | The \fBexec\fR command is not implemented and does not exist under Macintosh. | |
557 | .TP | |
558 | \fBUnix\fR\0\0\0\0\0\0\0 | |
559 | The \fBexec\fR command is fully functional and works as described. | |
560 | ||
561 | .SH "UNIX EXAMPLES" | |
562 | Here are some examples of the use of the \fBexec\fR command on Unix. | |
563 | .PP | |
564 | To execute a simple program and get its result: | |
565 | .CS | |
566 | \fBexec\fR uname -a | |
567 | .CE | |
568 | .PP | |
569 | To execute a program that can return a non-zero result, you should | |
570 | wrap the call to \fBexec\fR in \fBcatch\fR and check what the contents | |
571 | of the global \fBerrorCode\fR variable is if you have an error: | |
572 | .CS | |
573 | set status 0 | |
574 | if {[catch {\fBexec\fR grep foo bar.txt} results]} { | |
575 | if {[lindex $::errorCode 0] eq "CHILDSTATUS"} { | |
576 | set status [lindex $::errorCode 2] | |
577 | } else { | |
578 | # Some kind of unexpected failure | |
579 | } | |
580 | } | |
581 | .CE | |
582 | .PP | |
583 | When translating a command from a Unix shell invocation, care should | |
584 | be taken over the fact that single quote characters have no special | |
585 | significance to Tcl. Thus: | |
586 | .CS | |
587 | awk '{sum += $1} END {print sum}' numbers.list | |
588 | .CE | |
589 | would be translated into something like: | |
590 | .CS | |
591 | \fBexec\fR awk {{sum += $1} END {print sum}} numbers.list | |
592 | .CE | |
593 | .PP | |
594 | If you are converting invocations involving shell globbing, you should | |
595 | remember that Tcl does not handle globbing or expand things into | |
596 | multiple arguments by default. Instead you should write things like | |
597 | this: | |
598 | .CS | |
599 | eval [list \fBexec\fR ls -l] [glob *.tcl] | |
600 | .CE | |
601 | .PP | |
602 | .SH "WINDOWS EXAMPLES" | |
603 | Here are some examples of the use of the \fBexec\fR command on Windows. | |
604 | .PP | |
605 | To start an instance of \fInotepad\fR editing a file without waiting | |
606 | for the user to finish editing the file: | |
607 | .CS | |
608 | \fBexec\fR notepad myfile.txt & | |
609 | .CE | |
610 | .PP | |
611 | To print a text file using \fInotepad\fR: | |
612 | .CS | |
613 | \fBexec\fR notepad /p myfile.txt | |
614 | .CE | |
615 | .PP | |
616 | If a program calls other programs, such as is common with compilers, | |
617 | then you may need to resort to batch files to hide the console windows | |
618 | that sometimes pop up: | |
619 | .CS | |
620 | \fBexec\fR cmp.bat somefile.c -o somefile | |
621 | .CE | |
622 | With the file \fIcmp.bat\fR looking something like: | |
623 | .CS | |
624 | @gcc %1 %2 %3 %4 %5 %6 %7 %8 %9 | |
625 | .CE | |
626 | .PP | |
627 | Sometimes you need to be careful, as different programs may have the | |
628 | same name and be in the path. It can then happen that typing a command | |
629 | at the DOS prompt finds \fIa different program\fR than the same | |
630 | command run via \fBexec\fR. This is because of the (documented) | |
631 | differences in behaviour between \fBexec\fR and DOS batch files. | |
632 | .PP | |
633 | When in doubt, use the command \fBauto_execok\fR: it will return the | |
634 | complete path to the program as seen by the \fBexec\fR command. This | |
635 | applies especially when you want to run "internal" commands like | |
636 | \fIdir\fR from a Tcl script (if you just want to list filenames, use | |
637 | the \fBglob\fR command.) To do that, use this: | |
638 | .CS | |
639 | eval [list \fBexec\fR] [auto_execok dir] [list *.tcl] | |
640 | .CE | |
641 | ||
642 | .SH "SEE ALSO" | |
643 | error(n), open(n) | |
644 | ||
645 | .SH KEYWORDS | |
646 | execute, pipeline, redirection, subprocess |