Fastest way to check if a file exist using standard C++/C++11,14,17/C?

Well I threw together a test program that ran each of these methods 100,000 times, half on files that existed and half on files that didn't.

#include <sys/stat.h>#include <unistd.h>#include <string>#include <fstream>inline bool exists_test0 (const std::string& name) {    ifstream f(name.c_str());    return f.good();}inline bool exists_test1 (const std::string& name) {    if (FILE *file = fopen(name.c_str(), "r")) {        fclose(file);        return true;    } else {        return false;    }   }inline bool exists_test2 (const std::string& name) {    return ( access( name.c_str(), F_OK ) != -1 );}inline bool exists_test3 (const std::string& name) {  struct stat buffer;     return (stat (name.c_str(), &buffer) == 0); }

Results for total time to run the 100,000 calls averaged over 5 runs,

The stat() function provided the best performance on my system (Linux, compiled with g++), with a standard fopen call being your best bet if you for some reason refuse to use POSIX functions.

Remark : in C++14 and as soon as the filesystem TS will be finished and adopted, the solution will be to use:

std::experimental::filesystem::exists("helloworld.txt");

and since C++17, only:

std::filesystem::exists("helloworld.txt");

I use this piece of code, it works OK with me so far. This does not use many fancy features of C++:

bool is_file_exist(const char *fileName){    std::ifstream infile(fileName);    return infile.good();}