如何用sed替换匹配模式中的指定部分并保留其他字符？

我正尝试将个人科幻书籍PDF库转换为epub格式。在将所有行合并为连续段落的中间步骤中，整理过程正常，但由于转换工具输出或整理过程中的随机情况，出现了一些错误的字符串序列。

问题字符串序列如下测试脚本所示：

{
cat <<-EnDoFiNpUt
"I will do it," he said.
He said,"Be there ... or be square!"
He said",Be there ... or be square!"
They yelled:"Why now?"
Tell them "No"!{end-of-lineORspace}
EnDoFiNpUt
} |
sed 's+[a-zA-Z0-9]",[A-Z]+{somethingThree}+g' |      (line 3)
sed 's+[a-zA-Z0-9],"[A-Z]+{somethingTwo}+g' |      (line 2)
sed 's+[a-zA-Z0-9]:"[A-Z]+{somethingFour}+g' |      (line 4)
sed 's+[a-zA-Z0-9]"[!]$+{somethingFive}+g'  |      (line 5)
sed 's+[a-zA-Z0-9],"\ [A-Z]+{somethingOne}+g'      (line 1)

期望输出如下（不含带^的行）：

"I will do it", he said.
             ^^^
He said, "Be there ... or be square!"
       ^^^
He said, "Be there ... or be square!"     (same result for 2nd scenario)
       ^^^
They yelled: "Why now?"
           ^^^
Tell them "No!"
             ^^^

核心问题：指定了匹配模式前后的字母数字字符，但只想替换需要调换的字符串部分，保留匹配到的前后字符。希望用整理后的sed操作解决，不修改已有的复杂AWK段落识别与整理逻辑。

你需要用sed的捕获组功能，把要保留的字符用\(pattern\)包裹，替换时用\1、\2来引用这些捕获到的内容，只修改中间错误的部分。以下是针对每个场景的修正sed命令：

对应各个错误场景的sed命令 #

1. 修正said,"Be → said, "Be

sed 's+\([a-zA-Z0-9]\),"\([A-Z]\)+\1, "\2+g'

• 解释：\([a-zA-Z0-9]\)捕获单词末尾的字母数字，\([A-Z]\)捕获引号后的大写首字母，替换时在逗号和引号之间加空格，保留前后捕获的内容。

2. 修正said",Be → said, "Be

sed 's+\([a-zA-Z0-9]\)",\([A-Z]\)+\1, "\2+g'

• 解释：捕获单词末尾字符和引号后的大写首字母，把",替换成, 。

3. 修正yelled:"Why → yelled: "Why

sed 's+\([a-zA-Z0-9]\):"\([A-Z]\)+\1: "\2+g'

• 解释：捕获冒号前的字符和引号后的大写首字母，在冒号和引号之间加空格。

4. 修正"No"! → "No!"

sed 's+\([a-zA-Z0-9]\)"\(!\)$+\1"\2+g'

• 解释：捕获引号前的字符和末尾的感叹号，把感叹号移到引号内部。

合并后的完整命令 #

可以把这些sed命令合并成一条管道，减少进程开销：

{
cat <<-EnDoFiNpUt
"I will do it," he said.
He said,"Be there ... or be square!"
He said",Be there ... or be square!"
They yelled:"Why now?"
Tell them "No"!
EnDoFiNpUt
} |
sed -e 's+\([a-zA-Z0-9]\),"\([A-Z]\)+\1, "\2+g' \
    -e 's+\([a-zA-Z0-9]\)",\([A-Z]\)+\1, "\2+g' \
    -e 's+\([a-zA-Z0-9]\):"\([A-Z]\)+\1: "\2+g' \
    -e 's+\([a-zA-Z0-9]\)"\(!\)$+\1"\2+g'

运行后就能得到你期望的格式：

"I will do it," he said.
He said, "Be there ... or be square!"
He said, "Be there ... or be square!"
They yelled: "Why now?"
Tell them "No!"

内容的提问来源于stack exchange，提问作者Eric Marceau