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关于嵌入式编程的tcl语法的资料

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<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12"> 
#!/usr/bin/tclsh
#
# Demonstrate global variables
# and backslash substitution
 
if {$argc &gt;= 1} {
    set N 1
    foreach Arg $argv {
        puts stdout "$N: $Arg\n"
        set N [expr $N + 1]
        if {$Arg == "ring"} {
            puts stdout "\a"
        }
    }
} else {
    puts stdout "$argv0 on \
        X Display $env(DISPLAY)\n"
}

***
~/tcltk$ <b>./hello3.tcl</b>
./hello3.tcl on  X Display :0.0
 
~/tcltk$ <b>./hello3.tcl ring</b>
1: ring
			</code>
</pre>
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<td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>Tcl 全局变量和反斜杠替代</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>   第 3 页（共15 页）</nobr></font></td>
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<font size="2" face="Verdana, Arial, Helvetica">
<p>当 Tcl/Tk 脚本开始运行时，存在几个全局变量（如果在当前环境中为非空，则是预先定义的）。这些变量允许如下对操作系统进行访问：<i>argc</i> 是对脚本自变量的计数，而不是对调用的名称进行计数。				<i>argv</i> 是自变量的列表（不是数组）。<i>argv0</i> 是调用的文件名（可以是符号链接）。<i>env</i> 是根据当前
外壳的环境变量名建立下标的数组。<i>errorCode</i> 存储有关最近的 Tcl 错误信息，<i>errorInfo</i> 包含对这同一个错误事件的堆栈跟踪。
该列表还有另外 12 个 <i>tcl_xxx</i> 变量，从 <code>tcl_interactive</code> 到 <code>tcl_version</code>。可以在 <i>Tcl/Tk in a Nutshell</i> 中找到好的总结，（有关更多信息，请参阅本教程末尾的&ldquo;参考资料&rdquo;）。</p>
<p>在左边的样本代码中，使用了其中几个变量以及（又一次）使用了一些反斜杠引用的字符（\n 和 \a）。				<code>
							<b>\</b>
							<i>char</i>
						</code> 允许替代非打印 ASCII 字符。这对于 UNIX 下的许多脚本语言和外壳环境都是常见的。如表中说明的那样，对于没有定义替代的反斜杠引用的字符只被简单地回送到输出。</p>
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<th align="center" width="150pt">\<i>字符</i>
							</th><th align="center" width="150pt">替代</th>
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								<b>\a</b>
							</td><td width="150pt">响铃</td>
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								<b>\b</b>
							</td><td width="150pt">退格</td>
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<td width="150pt">
								<b>\f</b>
							</td><td width="150pt">换页</td>
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								<b>\n 或 \newline</b>
							</td><td width="150pt">新行</td>
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								<b>\r</b>
							</td><td width="150pt">回车</td>
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<td width="150pt">
								<b>\t</b>
							</td><td width="150pt">水平制表</td>
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								<b>\v</b>
							</td><td width="150pt">垂直制表</td>
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								<b>\space ("\ ")</b>
							</td><td width="150pt">空格</td>
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<td width="150pt">
								<b>\<i>ddd</i>
								</b>
							</td><td width="150pt">八进制值</td>
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<td width="150pt">
								<b>\x<i>ddd</i>...</b>
							</td><td width="150pt">十六进制值</td>
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<td width="150pt">
								<b>\c</b>
							</td><td width="150pt">回显&lsquo;c&rsquo;</td>
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<td width="150pt">
								<b>\\</b>
							</td><td width="150pt">反斜杠</td>
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