In C++, std::string::find() searches a string for a word or one character. It returns the index where the first match starts. Counting starts at 0, so the first character is index 0.
You can search from the beginning, or start later by passing a position. If the text is not there, the result is std::string::npos, not an error and not -1. Include <string>.
Call find on the string you already have. Start with these two lines.
text.find("C++");
text.find("C++", 4);| Call | What it does |
|---|---|
text.find("C++") | Looks through the whole string, from the first character. |
text.find("C++", 4) | Skips everything before index 4, then looks. Use this only when you want a later match. |
For one character, use single quotes: text.find('C').
size_t find(const string& str, size_t pos = 0) const;
size_t find(const char* s, size_t pos, size_t count) const;
size_t find(const char* s, size_t pos = 0) const;
size_t find(char ch, size_t pos = 0) const;| Parameter | Description |
|---|---|
| str | Required. The text to search for. Use quotes for a word, or single quotes for one character. |
| pos | Optional. Where the search starts. Leave it out to start at the beginning (0). |
| Return Value | Description |
|---|---|
| Index | The position of the first occurrence of the substring. |
std::string::npos | Returned if the substring is not found. |
find()Find "C++" and print its index.
#include <iostream>
#include <string>
int main() {
std::string text = "Hello, C++!";
std::size_t pos = text.find("C++");
if (pos != std::string::npos) {
std::cout << "Found at index: " << pos << '\n';
} else {
std::cout << "Not found.\n";
}
return 0;
}find("C++") scans left to right.7.npos before printing the index.npos)Missing text returns npos.
#include <iostream>
#include <string>
int main() {
std::string email = "[email protected]";
std::size_t at = email.find('@');
std::size_t hash = email.find('#');
std::cout << "At sign index: " << at << '\n';
if (hash == std::string::npos) {
std::cout << "No hash symbol.\n";
}
return 0;
}find('@') finds the character at index 4.find('#') returns npos.npos check.Pass pos to find the next match.
#include <iostream>
#include <string>
int main() {
std::string word = "banana";
std::size_t first = word.find("na");
std::size_t second = word.find("na", first + 1);
std::cout << "First: " << first << '\n';
std::cout << "Second: " << second << '\n';
return 0;
}"na" starts at index 2.first + 1.4.Append one C-string onto another with <cstring>.
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