std::regex_replace only first occurence

Question

std::regex_replace (Added in C++ 11) replaces all the occurrences. How can I make it replace only the first occurrence?

Micha Wiedenmann · Accepted Answer · 2021-04-06 07:35:21Z

14

If the flags parameter to std::regex_replace contains std::regex_constants::format_first_only, only the first match is replaced.

std::regex_replace("12 34",
                   std::regex(R"(\d+)"),
                   "num",
                    std::regex_constants::format_first_only);

stribizhev kindly provided a working example.

edited Apr 6, 2021 at 7:35

answered Oct 13, 2015 at 14:43

Micha Wiedenmann

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3 Comments

Wiktor Stribiżew Over a year ago

I was writing it as I did not want to post without an example :( Here is the snippet.

Shah Rukh Qasim Over a year ago

regex_replace("231 is my string 1", regex("\\d+"), string("number"), std::tr1::regex_constants::format_first_only);

Micha Wiedenmann Over a year ago

@stribizhev Thank you, I feel sorry for you put in more effort.

Shah Rukh Qasim · Accepted Answer · 2015-10-13 14:43:38Z

2

I found the solution myself. Posting for others if they face the same issue. Add:

std::tr1::regex_constants::format_first_only

to replace only the first occurrence as the fourth argument to regex_replace

answered Oct 13, 2015 at 14:43

Shah Rukh Qasim

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