std::string::find 参考

http://www.cplusplus.com/reference/string/string/find/

std::string::find

• C++98
• C++11
•  

string (1)	size_t find (const string& str, size_t pos = 0) const;
c-string (2)	size_t find (const char* s, size_t pos = 0) const;
buffer (3)	size_t find (const char* s, size_t pos, size_t n) const;
character (4)	size_t find (char c, size_t pos = 0) const;

Find content in string

Searches the string for the first occurrence of the sequence specified by its arguments.

When pos is specified, the search only includes characters at or after position pos, ignoring any possible occurrences that include characters before pos.

Notice that unlike member find_first_of, whenever more than one character is being searched for, it is not enough that just one of these characters match, but the entire sequence must match.

 

Parameters

str

Another string with the subject to search for.

pos

Position of the first character in the string to be considered in the search.
If this is greater than the string length, the function never finds matches.
Note: The first character is denoted by a value of 0 (not 1): A value of 0 means that the entire string is searched.

s

Pointer to an array of characters.
If argument n is specified (3), the sequence to match are the first n characters in the array.
Otherwise (2), a null-terminated sequence is expected: the length of the sequence to match is determined by the first occurrence of a null character.

n

Length of sequence of characters to match.

c

Individual character to be searched for.

size_t is an unsigned integral type (the same as member type string::size_type).

 

Return Value

The position of the first character of the first match.
If no matches were found, the function returns string::npos.

size_t is an unsigned integral type (the same as member type string::size_type).

 

Example

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// string::find #include // std::cout #include // std::string int main () { std::string str ("There are two needles in this haystack with needles."); std::string str2 ("needle"); // different member versions of find in the same order as above: std::size_t found = str.find(str2); if (found!=std::string::npos) std::cout << "first 'needle' found at: " << found << '\n'; found=str.find("needles are small",found+1,6); if (found!=std::string::npos) std::cout << "second 'needle' found at: " << found << '\n'; found=str.find("haystack"); if (found!=std::string::npos) std::cout << "'haystack' also found at: " << found << '\n'; found=str.find('.'); if (found!=std::string::npos) std::cout << "Period found at: " << found << '\n'; // let's replace the first needle: str.replace(str.find(str2),str2.length(),"preposition"); std::cout << str << '\n'; return 0; }

Edit & Run

Notice how parameter pos is used to search for a second instance of the same search string. Output:

first 'needle' found at: 14 second 'needle' found at: 44 'haystack' also found at: 30 Period found at: 51 There are two prepositions in this haystack with needles.