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，其中在每个内联方程式之前和之后使用单个 $ 分隔符。

我想在一个段落中找到每个方程，并用 XML 开始和结束标记替换分隔符 ....

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，但没有这两个方程之间的方程：

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，它可以考虑到不用作 LaTeX 分隔符的单个 $ 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 写作。

Answer 1

注意：此答案的第一部分仅关注替换成对的$'s；对于 OP 要求 不 替换独立 $'s ... 请参阅答案的第二半。

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替换成对的$'s

样本数据：

$ 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] - 匹配非文字 $ 的所有内容（在这种情况下，$'s 对之间的所有内容）
• \$ - 匹配文字 $
• <equation>\1</equation> - 将匹配的字符串替换为 <equation> + contents of capture group + </equation>
• /g - 根据需要重复搜索/替换

这会生成：

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

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处理独立的$

如果可以转义独立的$（例如\$），一个想法是让sed 将其替换为无意义的文字，执行<equation> / </equation> 替换，然后将无意义的文字改回@ 987654346@.

样本数据：

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

原来的sed 解决方案与新的替代品：

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

我们将\$ 替换为LITDOL (LITeral DOLlar)，执行我们原来的替换，然后将LITDOL 切换回\$。

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>

Answer 2

使用负前瞻试试这个 Perl。

$ cat joseph.txt
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... $fourth equation$
$ perl -p -e 's/(\$)(?![\d.]+)(.+?)(\$)/<equation>$2<\/equation>/g' joseph.txt
This is the beginning of a paragraph <equation>first equation</equation> ...and here is some text that includes a single dollar sign: He paid $2.50 for a pack of cigarettes... <equation>second equation</equation> ...and here is more text... <equation>third equation</equation> ...and here is yet more text... <equation>fourth equation</equation>
$