How to check if string ends with .txt

Question

I am learning basic C++, and right now I have gotten a string from a user and I want to check if they typed the entire file name (including .txt) or not. I have the string,

Answer 1

Unfortunately this useful function is not in the standard library. It is easy to write.

bool has_suffix(const std::string &str, const std::string &suffix)
{
    return str.size() >= suffix.size() &&
           str.compare(str.size() - suffix.size(), suffix.size(), suffix) == 0;
}

Answer 2

2 options I can think of beside mentioned ones:
1) regex - prob overkill for this, but simple regexes are nice and readable IMHO
2) rbegin - kind of nice, could be I am missing something, but here it is:

bool ends_with(const string& s, const string& ending)
{
return (s.size()>=ending.size()) && equal(ending.rbegin(), ending.rend(), s.rbegin());
}

http://coliru.stacked-crooked.com/a/4de3eafed3bff6e3

Answer 3

Using boost ends_with predicate:

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

if (boost::ends_with(fileName, ".txt")) { /* ... */ }

Answer 4

This should do it.

bool ends_with(const std::string & s, const std::string & suffix) {
     return s.rfind(suffix) == s.length() - suffix.length();
}

Verify here

Answer 5

This is something that, unfortunately enough, is not present in the standard library and it's also somewhat annoying to write. This is my attempt:

bool ends_with(const std::string& str, const std::string& end) {
    size_t slen = str.size(), elen = end.size();
    if (slen < elen) return false;
    while (elen) {
        if (str[--slen] != end[--elen]) return false;
    }
    return true;
}