如何在纯C中进行正则表达式字符串替换?

I've looked at the regex functions in the POSIX regex library and the PCRE library, but both of them don't seem to have a string replacement function. I don't want to use C++, and it would be best if I don't need to link another library (but I can if I have to). Do I need to manually do the string replacing? If so, how can I use capture groups?I've looked at the regex functions in the POSIX