std::sub_match<BidirIt>::length

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< cpp‎ | regex‎ | sub match
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std::sub_match
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sub_match::length
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(until C++20) (until C++20) (until C++20) (until C++20) (until C++20) (C++20)
difference_type length() const;

Returns the number of characters in the match.

Return value

std::distance(first, second) if the match is valid, ​0​

Complexity

Constant.

Example

Run this code
#include <iostream>
#include <regex>
#include <string>
 
int main()
{
    std::string sentence{"Quick red fox jumped over a lazy cow."};
    const std::regex re{"([A-z]+) ([a-z]+) ([a-z]+) ([a-z]+)"};
    std::smatch words;
    std::regex_search(sentence, words, re);
    for (const auto& m : words)
        std::cout << '[' << m << "], length = " << m.length() << '\n';
}

Output: 

[Quick red fox jumped], length = 20
[Quick], length = 5
[red], length = 3
[fox], length = 3
[jumped], length = 6
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