C++ check if string is space or null

Question

Basically I have string of whitespace " " or blocks of whitespace or "" empty in some of the lines of the files and I would like to know if there is a function in C++ that checks this.

*note:* As a side question, in C++ if I want to break a string down and check it for a pattern which library should I use? If I want to code it myself which basic functions should I know to manipulate string? Are there any good references?

Answer 1

bool isWhitespace(std::string s){
    for(int index = 0; index < s.length(); index++){
        if(!std::isspace(s[index]))
            return false;
    }
    return true;
}

Answer 2

std::string str = ...;
if (str.empty() || str == " ") {
    // It's empty or a single space.
}