src/mann/catch.n

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   8 '\" RCS: @(#) $Id: catch.n,v 1.2 2003/11/24 05:09:59 bbbush Exp $
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  10 '\" The definitions below are for supplemental macros used in Tcl/Tk
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 207 .de SO
 208 .SH "STANDARD OPTIONS"
 209 .LP
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 211 .ta 5.5c 11c
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 215 .de SE
 216 .fi
 217 .ft R
 218 .LP
 219 See the \\fBoptions\\fR manual entry for details on the standard options.
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 222 .de OP
 223 .LP
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 225 .ta 4c
 226 Command-Line Name:      \\fB\\$1\\fR
 227 Database Name:  \\fB\\$2\\fR
 228 Database Class: \\fB\\$3\\fR
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 243 .de UL
 244 \\$1\l'|0\(ul'\\$2
 245 ..
 246 .TH catch 3tcl "8.0" Tcl "Tcl Built-In Commands"
 247 .BS
 248 '\" Note:  do not modify the .SH NAME line immediately below!
 249 .SH NAME
 250 catch \- 对脚本求值并追踪异常返回
 251 .SH "总览 SYNOPSIS"
 252 \fBcatch\fI script \fR?\fIvarName\fR?
 253 .BE
 254
 255 .SH "描述 DESCRIPTION"
 256 .PP
 257 \fBcatch\fR 命令被用于防止出错导致的终止命令解释。\fBCatch\fR   递归的调用 Tcl 解释器来执行 \fIscript\fR，并且不顾在执行 \fIscript \fR期间可能发生的任何错误，它总是返回而不引发(raise)任何错误。
 258 .PP
 259 如果 \fIscript\fR  引发一个错误，\fBcatch\fR  将返回一个非零的整数值，相应于异常返回代码中的一个(参见 tcl.h 来找到代码值的定义)。如果给出了 \fIvarName\fR  参数，则它所指名的变量被设置成从解释 \fIscript \fR得到的错误消息。
 260 .PP
 261 如果 \fIscript\fR  不引发任何错误，\fBcatch\fR  将返回 0(TCL_OK)并设置这个变量为脚本返回的值。
 262 .PP
 263 注意 \fBcatch\fR  捕获所有的例外，如同错误一样，包括了由 \fB break \fR 和 \fB continue \fR  生成的例外。唯一不捕获的错误是在编译脚本时发现的语法错误。这是因为 catch 命令只捕捉运行时的错误。当 catch 语句被编译后，脚本同样要被编译，并且任何错误都将生成一个 Tcl 错误。
 264
 265 .SH EXAMPLES
 266
 267 \fBcatch\fR  命令可在一个 \fB if \fR  中使用，基于一个脚本的(是否)成功而(进行)分支(branch)。
 268
 269 .CS
 270 if { [catch {open $someFile w} fid] } {
 271     puts stderr "Could not open $someFile for writing\\n$fid"
 272     exit 1
 273 }
 274 .CE
 275 \fBcatch\fR  命令不捕捉编译后的语法错误。第一次调用 proc \fBfoo\fR  时，(过程)体将被编译并且生成一个  Tcl 错误。
 276
 277 .CS
 278 proc foo {} {
 279     catch {expr {1 +- }}
 280 }
 281 .CE
 282
 283 .SH "关键字 KEYWORDS"
 284 catch, error
 285 .SH "[中文版维护人]"
 286 .B 寒蝉退士
 287 .SH "[中文版最新更新]"
 288 .B 2001/06/21
 289 .SH "《中国 Linux 论坛 man 手册页翻译计划》:"
 290 .BI http://cmpp.linuxforum.net