Logical block (LBA) information of a file

Question

*How we can find out the Logical Block Address (LBA) of a file blocks. We need to find out the blocks which are using for storing a file in Memory.*

Answer 1

* log2phys.c - this Mac OS X program attempts to provide a physical disk
* map for the specified file(s).
* This is an EXPERIMENT! I think the code does what it says,
* but I have not verified the results.
* Bob Harris 14-Apr-2010 o initial coding
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#define STRIDE (4096) /* ASSUMES the allocation unit is 4K */
void log2phys(char *file);
int
main(int ac, char **av)
int n;
if ( ac < 2 ) {
fprintf(stderr, "Usage: log2phys file [file ...]
exit(EXIT_FAILURE);
for(n=1; n < ac; n++) {
log2phys(av[n]);
exit(EXIT_SUCCESS);
void
log2phys(char *file)
int fd;
int sts;
off_t offset;
off_t previous;
off_t length;
struct log2phys phys;
printf("%s
", file); /* display the file name */
fd = open(file, O_RDONLY); /* open the file */
if ( fd < 0 ) {
fprintf(stderr,"open(%s,O_RDONLY)", file);
perror(" ");
exit(EXIT_FAILURE);
* Seek through the file 4K at a time, and obtain the disk offset
sts = 0;
previous = (off_t)-1;
length = 0;
for(offset=0; sts >= 0; offset += STRIDE) {
/* position to next offset in the file */
sts = lseek(fd, offset, SEEK_SET);
if ( sts < 0 ) {
fprintf(stderr,"lseek(%d, %lld, SEEK_SET)", fd, offset);
perror(" ");
exit(EXIT_FAILURE);
/* fetch the current physical location for file offset */
sts = fcntl(fd, F_LOG2PHYS, &phys);
if ( sts < 0 && errno == ERANGE ) {
/* we have gone past the end of the file */
break;
else if ( sts < 0 ) {
fprintf(stderr,"fcntl(%d, F_LOG2PHYS, &phys)", fd);
perror(" ");
exit(EXIT_FAILURE);
* Figure out if this is a non-contiguous allocation unit
if ( previous + length != phys.l2p_devoffset ) {
if ( length != 0 ) {
* We have accumulated some length from the previous run of
* allocation units, so display the length of the previous
* starting offset
printf(" length= %11lld
", length);
length = 0;
/* Display the offset of this new run of allocation units */
printf(" file_offset= %10lld volume_offset= %17lld",
offset, phys.l2p_devoffset);
/* save the new previous starting physical offset */
previous = phys.l2p_devoffset;
/* Count this allocation unit as part of the length */
length += STRIDE;
* Print the final length.
if ( length ) {
printf(" length= %11lld
", length);
close(fd);