Check if a string contains a string in C++

I have a variable of type std::string. I want to check if it contains a certain std::string. How would I do that?

Is there a function that returns true if the string is found, and false if it isn't?

Use std::string::find as follows:

if (s1.find(s2) != std::string::npos) {
    std::cout << "found!" << '\n';
}

Note: "found!" will be printed if s2 is a substring of s1, both s1 and s2 are of type std::string.

You can try using the find function:

string str ("There are two needles in this haystack.");
string str2 ("needle");

if (str.find(str2) != string::npos) {
//.. found.
} 

Starting from C++23 you can use std::string::contains

#include <string>

const auto haystack = std::string("haystack with needles");
const auto needle = std::string("needle");

if (haystack.contains(needle))
{
    // found!
}

Actually, you can try to use boost library,I think std::string doesn't supply enough method to do all the common string operation.In boost,you can just use the boost::algorithm::contains:

#include <string>
#include <boost/algorithm/string.hpp>

int main() {
    std::string s("gengjiawen");
    std::string t("geng");
    bool b = boost::algorithm::contains(s, t);
    std::cout << b << std::endl;
    return 0;
}