What is the fastest way to overwrite an entire file with zeros in C?

Question

What I need to do is to fill the entire file contents with zeros in the fastest way. I know some linux commands like cp actually gets what is the best block siz

Answer 1

This is my idea; notice I removed every error checking code for clarity.

int f = open("file", "w");             // open file
int len = lseek(f, 0, SEEK_END);       // and get its length
lseek(f, 0, SEEK_BEG);                 // then go back at the beginning
char *buff = malloc(len);              // create a buffer large enough
memset(buff, 0, len);                  // fill it with 0s
write(f, buff, len);                   // write back to file
close(f);                              // and close