How to check if file exists in C++ in a portable way? -

currently use code check if file exists on windows , posix-compatible oses (linux, android, macos, ios, blackberry 10):

bool fileexist( const std::string& name ) { #ifdef os_windows     struct _stat buf;     int result = _stat( name.c_str(), &buf ); #else     struct stat buf;     int result = stat( name.c_str(), &buf ); #endif     return result == 0; } 

questions:

1. does code have pitfalls? (maybe os cannot compiled)

2. is possible in portable way using c/c++ standard library?

3. how improve it? looking canonical example.

because c++ tagged, use boost::filesystem:

#include <boost/filesystem.hpp>  bool fileexist( const std::string& name ) {      return boost::filesystem::exists(name); } 

behind scenes

apparently, boost using stat on posix , dword attr(::getfileattributesw(filename)); on windows (note: i've extracted relevant parts of code here, did wrong, should it).

basically, besides return value, boost checking errno value in order check if file not exist, or stat failed different reason.

#ifdef boost_posix_api  struct stat path_stat; if (::stat(p.c_str(), &path_stat)!= 0) {   if (ec != 0)                            // report errno, though     ec->assign(errno, system_category());   // errno values not status_errors    if (not_found_error(errno))   {     return fs::file_status(fs::file_not_found, fs::no_perms);   }   if (ec == 0)     boost_filesystem_throw(filesystem_error("boost::filesystem::status",       p, error_code(errno, system_category())));   return fs::file_status(fs::status_error); }  #else      dword attr(::getfileattributesw(p.c_str()));      if (attr == 0xffffffff)      {          int errval(::getlasterror());          if (not_found_error(errval))          {              return fs::file_status(fs::file_not_found, fs::no_perms);          }      }    #endif 

not_found_error defined separately windows , posix:

windows:

bool not_found_error(int errval)   {     return errval == error_file_not_found       || errval == error_path_not_found       || errval == error_invalid_name  // "tools/jam/src/:sys:stat.h", "//foo"       || errval == error_invalid_drive  // usb card reader no card inserted       || errval == error_not_ready  // cd/dvd drive no disc inserted       || errval == error_invalid_parameter  // ":sys:stat.h"       || errval == error_bad_pathname  // "//nosuch" on win64       || errval == error_bad_netpath;  // "//nosuch" on win32   } 

posix:

bool not_found_error(int errval)   {     return errno == enoent || errno == enotdir;   }