Question

In my C/C++ program I need to check if the file from what I read have been overwrote (its inode was changed or some new lines were added). If I’m now wrong fstat and fstat64 can be usefull only when I use Linux but not for windows. Is there any universal (to work for complex OSes) way to do this? And also can you tell me how do this using fstat64?

Answer 1

You can keep track of when the file was last written to know if it has been modified. The cross platform solution is using boost::filesystem. Windows doesn’t have fstat64 AFAIK.

http://www.boost.org/doc/libs/1_44_0/libs/filesystem/v2/doc/index.htm

http://rosettacode.org/wiki/File_modification_time#C.2B.2B

#include <boost/filesystem/operations.hpp>
#include <ctime>
#include <iostream>

int main( int argc , char *argv[ ] ) {
   if ( argc != 2 ) {
      std::cerr << "Error! Syntax: moditime <filename>!\n" ;
      return 1 ;
   }
   boost::filesystem::path p( argv[ 1 ] ) ;
   if ( boost::filesystem::exists( p ) ) {
      std::time_t t = boost::filesystem::last_write_time( p ) ;
      std::cout << "On " << std::ctime( &t ) << " the file " << argv[ 1 ] 
     << " was modified the last time!\n" ;
      std::cout << "Setting the modification time to now:\n" ;
      std::time_t n = std::time( 0 ) ;
      boost::filesystem::last_write_time( p , n ) ; 
      t = boost::filesystem::last_write_time( p ) ;
      std::cout << "Now the modification time is " << std::ctime( &t ) << std::endl ;
      return 0 ;
  } else {
      std::cout << "Could not find file " << argv[ 1 ] << '\n' ;
      return 2 ;
  }

}