I everybody!!
How can i use statvfs() to calculate disk usage and free disk space??

Im using this code:

/* Any file on the filesystem in question */
char *filename = "/home/nesto/test/test.cpp";

struct statvfs buf;
if (!statvfs(filename, &buf)) {

unsigned long blksize, blocks, freeblks, disk_size, used, free;
blksize = buf.f_bsize;
blocks = buf.f_blocks;
freeblks = buf.f_bfree;
disk_size = blocks * blksize;
free = freeblks * blksize;
used = disk_size - free; printf("Disk usage : %lu \t Free space %lu\n", used, free);

} else {

printf("Couldn't get file system statistics\n");
}
return 0;

But when i execute "df ." the values dont match
Can anyone help me.

Best regards to all

Two points:

POSIX df reports blocks, you are reporting blocks * blocksize

Since you are reporting on a filesystem, other users can create/delete files,
so that in the time you run your code, exit, and then do a df, a lot can happen.