2 '\" Copyright (c) 2008 Donal K. Fellows
4 '\" See the file "license.terms" for information on usage and redistribution
5 '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
7 .TH try n 8.6 Tcl "Tcl Built-In Commands"
8 .\" The -*- nroff -*- definitions below are for supplemental macros used
9 .\" in Tcl/Tk manual entries.
11 .\" .AP type name in/out ?indent?
12 .\" Start paragraph describing an argument to a library procedure.
13 .\" type is type of argument (int, etc.), in/out is either "in", "out",
14 .\" or "in/out" to describe whether procedure reads or modifies arg,
15 .\" and indent is equivalent to second arg of .IP (shouldn't ever be
16 .\" needed; use .AS below instead)
19 .\" Give maximum sizes of arguments for setting tab stops. Type and
20 .\" name are examples of largest possible arguments that will be passed
21 .\" to .AP later. If args are omitted, default tab stops are used.
24 .\" Start box enclosure. From here until next .BE, everything will be
25 .\" enclosed in one large box.
28 .\" End of box enclosure.
31 .\" Begin code excerpt.
36 .\" .VS ?version? ?br?
37 .\" Begin vertical sidebar, for use in marking newly-changed parts
38 .\" of man pages. The first argument is ignored and used for recording
39 .\" the version when the .VS was added, so that the sidebars can be
40 .\" found and removed when they reach a certain age. If another argument
41 .\" is present, then a line break is forced before starting the sidebar.
44 .\" End of vertical sidebar.
47 .\" Begin an indented unfilled display.
50 .\" End of indented unfilled display.
53 .\" Start of list of standard options for a Tk widget. The manpage
54 .\" argument defines where to look up the standard options; if
55 .\" omitted, defaults to "options". The options follow on successive
56 .\" lines, in three columns separated by tabs.
59 .\" End of list of standard options for a Tk widget.
61 .\" .OP cmdName dbName dbClass
62 .\" Start of description of a specific option. cmdName gives the
63 .\" option's name as specified in the class command, dbName gives
64 .\" the option's name in the option database, and dbClass gives
65 .\" the option's class in the option database.
68 .\" Print arg1 underlined, then print arg2 normally.
71 .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation).
74 .\" Print an open parenthesis, arg1 in quotes, then arg2 normally
75 .\" (for trailing punctuation) and then a closing parenthesis.
77 .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
81 .\" # Start an argument description
85 . ie !"\\$2"" .TP \\n()Cu
90 \&\\$1 \\fI\\$2\\fP (\\$3)
103 .\" # define tabbing values for .AP
106 .if !"\\$1"" .nr )A \\w'\\$1'u+3n
109 .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
110 .nr )C \\n()Bu+\\w'(in/out)'u+2n
112 .AS Tcl_Interp Tcl_CreateInterp in/out
113 .\" # BS - start boxed text
114 .\" # ^y = starting y location
122 .if n \l'\\n(.lu\(ul'
125 .\" # BE - end boxed text (draw box now)
130 .ie n \l'\\n(^lu\(ul'
132 .\" Draw four-sided box normally, but don't draw top of
133 .\" box if the box started on an earlier page.
135 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
138 \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
145 .\" # VS - start vertical sidebar
146 .\" # ^Y = starting y location
147 .\" # ^v = 1 (for troff; for nroff this doesn't matter)
151 .ie n 'mc \s12\(br\s0
154 .\" # VE - end of vertical sidebar
162 \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
169 .\" # Special macro to handle page bottom: finish off current
170 .\" # box/sidebar if in box/sidebar mode, then invoked standard
171 .\" # page bottom macro.
178 .\" Draw three-sided box if this is the box's first page,
179 .\" draw two sides but no top otherwise.
180 .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
181 .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
184 .nr ^x \\n(^tu+1v-\\n(^Yu
185 \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
198 .\" # DS - begin display
204 .\" # DE - end display
210 .\" # SO - start of list of standard options
212 'ie '\\$1'' .ds So \\fBoptions\\fR
213 'el .ds So \\fB\\$1\\fR
214 .SH "STANDARD OPTIONS"
220 .\" # SE - end of list of standard options
225 See the \\*(So manual entry for details on the standard options.
227 .\" # OP - start of full description for a single option
232 Command-Line Name: \\fB\\$1\\fR
233 Database Name: \\fB\\$2\\fR
234 Database Class: \\fB\\$3\\fR
238 .\" # CS - begin code excerpt
244 .\" # CE - end code excerpt
249 .\" # UL - underline word
253 .\" # QW - apply quotation marks to word
255 .ie '\\*(lq'"' ``\\$1''\\$2
256 .\"" fix emacs highlighting
257 .el \\*(lq\\$1\\*(rq\\$2
259 .\" # PQ - apply parens and quotation marks to word
261 .ie '\\*(lq'"' (``\\$1''\\$2)\\$3
262 .\"" fix emacs highlighting
263 .el (\\*(lq\\$1\\*(rq\\$2)\\$3
265 .\" # QR - quoted range
267 .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3
268 .\"" fix emacs highlighting
269 .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3
271 .\" # MT - "empty" string
276 '\" Note: do not modify the .SH NAME line immediately below!
278 try \- Trap and process errors and exceptions
280 \fBtry\fI body\fR ?\fIhandler...\fR? ?\fBfinally\fI script\fR?
284 This command executes the script \fIbody\fR and, depending on what the outcome
285 of that script is (normal exit, error, or some other exceptional result), runs
286 a handler script to deal with the case. Once that has all happened, if the
287 \fBfinally\fR clause is present, the \fIscript\fR it includes will be run and
288 the result of the handler (or the \fIbody\fR if no handler matched) is allowed
289 to continue to propagate. Note that the \fBfinally\fR clause is processed even
290 if an error occurs and irrespective of which, if any, \fIhandler\fR is used.
292 The \fIhandler\fR clauses are each expressed as several words, and must have
293 one of the following forms:
295 \fBon \fIcode variableList script\fR
297 This clause matches if the evaluation of \fIbody\fR completed with the
298 exception code \fIcode\fR. The \fIcode\fR may be expressed as an integer or
299 one of the following literal words: \fBok\fR, \fBerror\fR, \fBreturn\fR,
300 \fBbreak\fR, or \fBcontinue\fR. Those literals correspond to the integers 0
301 through 4 respectively.
303 \fBtrap \fIpattern variableList script\fR
305 This clause matches if the evaluation of \fIbody\fR resulted in an error and
306 the prefix of the \fB\-errorcode\fR from the interpreter's status dictionary
307 is equal to the \fIpattern\fR. The number of prefix words taken from the
308 \fB\-errorcode\fR is equal to the list-length of \fIpattern\fR, and inter-word
309 spaces are normalized in both the \fB\-errorcode\fR and \fIpattern\fR before
312 The \fIvariableList\fR word in each \fIhandler\fR is always interpreted as a
313 list of variable names. If the first word of the list is present and
314 non-empty, it names a variable into which the result of the evaluation of
315 \fIbody\fR (from the main \fBtry\fR) will be placed; this will contain the
316 human-readable form of any errors. If the second word of the list is present
317 and non-empty, it names a variable into which the options dictionary of the
318 interpreter at the moment of completion of execution of \fIbody\fR
321 The \fIscript\fR word of each \fIhandler\fR is also always interpreted the
322 same: as a Tcl script to evaluate if the clause is matched. If \fIscript\fR is
325 and the \fIhandler\fR is not the last one, the \fIscript\fR of the following
326 \fIhandler\fR is invoked instead (just like with the \fBswitch\fR command).
328 Note that \fIhandler\fR clauses are matched against in order, and that the
329 first matching one is always selected. At most one \fIhandler\fR clause will
330 selected. As a consequence, an \fBon error\fR will mask any subsequent
331 \fBtrap\fR in the \fBtry\fR. Also note that \fBon error\fR is equivalent to
334 If an exception (i.e. any non-\fBok\fR result) occurs during the evaluation of
335 either the \fIhandler\fR or the \fBfinally\fR clause, the original exception's
336 status dictionary will be added to the new exception's status dictionary under
337 the \fB\-during\fR key.
340 Ensure that a file is closed no matter what:
343 set f [open /some/file/name a]
345 puts $f "some message"
352 Handle different reasons for a file to not be openable for reading:
356 set f [open /some/file/name w]
357 } \fBtrap\fR {POSIX EISDIR} {} {
358 puts "failed to open /some/file/name: it's a directory"
359 } \fBtrap\fR {POSIX ENOENT} {} {
360 puts "failed to open /some/file/name: it doesn't exist"
364 catch(n), error(n), return(n), throw(n)
366 cleanup, error, exception, final, resource management