regex - 在段落中查找匹配的字符串

Question

我有一个包含 LaTeX 数学方程式的 TXT 文件，其中每个内联方程式前后使用单个 $ 分隔符。

我想找到段落中的每个方程式，并用 XML 开始和结束标记替换定界符....

例如，

以下段落:

This is the beginning of a paragraph $first equation$ ...and here is some text... $second equation$ ...and here is more text... $third equation$ ...and here is yet more text... $fourth equation$

应该变成:

This is the beginning of a paragraph <equation>first equation</equation> ...and here is some text... <equation>second equation</equation> ...and here is more text... <equation>third equation</equation> ...and here is yet more text... <equation>fourth equation</equation>

我已经尝试过如下的 sed 和 perl 命令:

perl -p -e 's/(\$)(.*[^\$])(\$)/<equation>$2<\/equation>/'

但是这些命令会导致方程的第一个和最后一个实例被转换，但是这两个之间的方程都不会被转换:

This is the beginning of a paragraph <equation>first equation$ ...and here is some text... $second equation$ ...and here is more text... $third equation$ ...and here is yet more text... $fourth equation</equation>

我还想要一个强大的解决方案，它可以考虑不用作 LaTeX 定界符的单个 $ 的存在。例如，

This is the beginning of a paragraph $first equation$ ...and here is some text that includes a single dollar sign: He paid $2.50 for a pack of cigarettes... $second equation$ ...and here is more text... $third equation$ ...and here is yet more text... $fourth equation$

不会变成:

This is the beginning of a paragraph <equation>first equation$ ...and here is some text that includes a single dollar sign: He paid <equation>2.50 for a pack of cigarettes... $second equation$ ...and here is more text... $third equation$ ...and here is yet more text... $fourth equation</equation>

注意:我正在用 Bash 编写。

Answer 1

注意:此答案的第一部分仅关注替换 $'s 对;对于 OP 要求不替换独立的 $'s ...请参阅答案的第二部分。

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替换成对的 $'s

示例数据:

$ cat latex.txt
... $first equation$ ... $second equation$ ... $third equation$

一个sed想法:

sed -E 's|\$([^$]*)\$|<equation>\1</equation>|g' latex.txt

地点:

• -E - 启用扩展的正则表达式支持
• \$ - 匹配文字 $
• ([^$]*) - [捕获组 #1] - 匹配所有不是文字的 $ (在这种情况下，这对 $'s 之间的所有内容)
• \$ - 匹配文字 $
• <equation>\1</equation> - 用 <equation> 替换匹配的字符串+ contents of capture group + </equation>
• /g - 根据需要经常重复搜索/替换

这会产生:

... <equation>first equation</equation> ... <equation>second equation</equation> ... <equation>third equation</equation>

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处理独立 $

如果独立$可以转义(例如 \$ )一个想法是拥有 sed用无意义的文字替换它，执行 <equation> / </equation>替换，然后将无意义的文字改回 \$ .

示例数据:

$ cat latex.txt
... $first equation$ ... $second equation$ ... $third equation$
... $first equation$ ... \$3.50 cup of coffee ... $third equation$

原创 sed新替换的解决方案:

sed -E 's|\\\$|LITDOL|g;s|\$([^$]*)\$|<equation>\1</equation>|g;s|LITDOL|\\\$|g' latex.txt

我们在哪里替换 \$与 LITDOL (LITeral DOLlar)，执行我们原来的替换，然后切换 LITDOL返回\$ .

生成:

... <equation>first equation</equation> ... <equation>second equation</equation> ... <equation>third equation</equation>
... <equation>first equation</equation> ... \$3.50 cup of coffee ... <equation>third equation</equation>