Re: how copy file on linux?

On 28/06/2024 19:15, Bonita Montero wrote:

int fromFile = open( from, O_RDONLY | O_NOATIME );
     if( !fromFile )
         return false;
     invoke_on_destruct closeFrom( [&] { close( fromFile ); } );
 //    int toFile = open( to, O_CREAT );
 //    if( !toFile )
 //        return false;
     invoke_on_destruct closeTo( [&] { close( toFile ); } );
//     invoke_on_destruct delTo( [&] { unlink( to ); } );
     for( int64_t remaining = attrFrom.st_size; remaining > 0; remaining -= 0x100000 )
     {
         size_t n = (size_t)(remaining >= 0x100000 ? 0x100000 : remaining);
         buf.resize( n );
         if( read( fromFile, buf.data(), n ) )
         {
             // this branch is taken
             cout << strerror( errno ) << endl;
             return false;
         }

So it claims the file opens, then won't read it?
Check the call. Is 0 the success return?
Then I must admit I'm stumped. "to" doesn't alias "from" I suppose?
I'd also wonder if somehow the C++ compiler has invoked the on destruct code, and closed the file.
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