Question

I need to create a huge binary file filled with zeros in Windows OS. Its size is given. What’s the most efficient way to do it in C/C++?

Answer 1

Try calling truncate(2):

truncate("/my/file", my_size);

For more information,

man 2 truncate

The truncate() and ftruncate() functions cause the regular file named by path or referenced by fd to be truncated to a size of precisely length bytes.

If the file previously was larger than this size, the extra data is lost. If the file previously was shorter, it is extended, and the extended part reads as null bytes (‘\0’).

If you are looking for the Windows native function, take a look at SetEndOfFile, which does much the same thing.