Fabio Miranda Hamburger wrote: > I am curious about the mismatch between du and ls. Apparently, du reports > amount of 512 or 1024-K blocks, and ls lists the absolute value. du reports the amount of disk space which the file uses, while ls reports the amount of data which it contains. > But, why in some cases, a 1100 bytes file is reported by du as 4 x 512 > bytes instead of 3 x 512bytes Because the file occupies 2 x 1024-byte blocks. > I note both use fstat(). stat(), fstat() etc, and thus du, report disk usage in multiples of 512-byte blocks, as that was the block size on the earliest Unix systems. The actual block size depends upon the filesystem. The st_size field indicates the actual size of the file (i.e. the number of bytes which it contains); this is the value reported by ls. The st_blocks field returns the disk usage in multiples of 512 bytes; this is the value reported by du. Note that the actual size of the file can be more than 512 * st_blocks bytes if the file contains "holes". These are blocks which are implicitly filled with zeros when the file is enlarged by lseek(), ftruncate() etc, and aren't actually stored on disk. -- Glynn Clements <glynn@xxxxxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
