How to get USB connected hard disk serial in linux? - c

Question

I'm having a requirement to create a file in the externally mounted hard disk .created file should contain the serial no of the harddisk and that file can be used by other process.
I tried to use the following code
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/hdreg.h>
int main(int argc, char *argv[])
{
static struct hd_driveid hd;
int fd;
if (geteuid() > 0) {
printf("ERROR: Must be root to use\n");
exit(1);
}
if ((fd = open(argv[1], O_RDONLY|O_NONBLOCK)) < 0) {
printf("ERROR: Cannot open device %s\n", argv[1]);
exit(1);
}
if (!ioctl(fd, HDIO_GET_IDENTITY, &hd)) {
printf("Hard Disk Model: %.40s\n", hd.model);
printf(" Serial Number: %.20s\n", hd.serial_no);
} else if (errno == -ENOMSG) {
printf("No hard disk identification information available\n");
} else {
perror("ERROR: HDIO_GET_IDENTITY");
exit(1);
}
exit(0);
}
this is working fine for internal hard disk but when i do this for external hard disk(usb) it is giving me the following error
ERROR: HDIO_GET_IDENTITY: Invalid argument

Answer 1

Because the device is connected to a USB bridge, you can't send the HDIO_GET_IDENTITY command.
You can try hdparm to query the identity of the device. With the default options, hdparm fails to identify the device so you have to specify the type of the device with -d (see USB devices and smartmontools).
Without the -d option, I get:
$ sudo smartctl /dev/sdc
/dev/sdc: Unknown USB bridge [0x059f:0x1011 (0x000)]
Please specify device type with the -d option.
With -d sat,auto, hdparm manages to display some information about the device:
$ sudo smartctl -d sat,auto -i /dev/sdc
/dev/sdc [SCSI]: Device open changed type from 'sat,auto' to 'scsi'
=== START OF INFORMATION SECTION ===
Vendor: ST2000VN
Product: 000-1H3164
User Capacity: 2 000 398 934 016 bytes [2,00 TB]
Logical block size: 512 bytes
Device type: disk
Local Time is: Thu Mar 13 09:41:32 2014 CET
SMART support is: Unavailable - device lacks SMART capability.
You can try to do the same thing as smartctl in your C program, but it's probably easier to write a script that invokes smartctl.

Answer 2

Thanks for the explanation and i got the below to identify the serial no of a external hardisk
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <scsi/scsi.h>
#include <scsi/sg.h>
#include <sys/ioctl.h>
int scsi_get_serial(int fd, void *buf, size_t buf_len) {
// we shall retrieve page 0x80 as per http://en.wikipedia.org/wiki/SCSI_Inquiry_Command
unsigned char inq_cmd[] = {INQUIRY, 1, 0x80, 0, buf_len, 0};
unsigned char sense[32];
struct sg_io_hdr io_hdr;
int result;
memset(&io_hdr, 0, sizeof (io_hdr));
io_hdr.interface_id = 'S';
io_hdr.cmdp = inq_cmd;
io_hdr.cmd_len = sizeof (inq_cmd);
io_hdr.dxferp = buf;
io_hdr.dxfer_len = buf_len;
io_hdr.dxfer_direction = SG_DXFER_FROM_DEV;
io_hdr.sbp = sense;
io_hdr.mx_sb_len = sizeof (sense);
io_hdr.timeout = 5000;
result = ioctl(fd, SG_IO, &io_hdr);
if (result < 0)
return result;
if ((io_hdr.info & SG_INFO_OK_MASK) != SG_INFO_OK)
return 1;
return 0;
}
void trim(char * s) {
char * p = s;
int l = strlen(p);
while(isspace(p[l - 1])) p[--l] = 0;
while(* p && isspace(* p)) ++p, --l;
memmove(s, p, l + 1);
}
int storeData (char *filepath, char *data) {
int rc = 0;
FILE *fOut = fopen (filepath, "a");
if (fOut != NULL) {
if (fputs (data, fOut) != EOF) {
rc = 1;
}
fclose (fOut); // or for the paranoid: if (fclose (fOut) == EOF) rc = 0;
}
return rc;
}
int main(int argc, char** argv) {
if(argc>1){
char *dev = (char *)argv[1];
char outStr[1024];
printf("\nEntered Serial no : %s\n",argv[1]);
char scsi_serial[255];
int rc;
int fd;
fd = open(dev, O_RDONLY | O_NONBLOCK);
if (fd < 0) {
perror(dev);
}
memset(scsi_serial, 0, sizeof (scsi_serial));
rc = scsi_get_serial(fd, scsi_serial, 255);
// scsi_serial[3] is the length of the serial number
// scsi_serial[4] is serial number (raw, NOT null terminated)
if (rc < 0) {
printf("FAIL, rc=%d, errno=%d\n", rc, errno);
} else
if (rc == 1) {
printf("FAIL, rc=%d, drive doesn't report serial number\n", rc);
} else {
if (!scsi_serial[3]) {
printf("Failed to retrieve serial for %s\n", dev);
return -1;
}
printf("Serial Number: %.*s\n", (size_t) scsi_serial[3], (char *) & scsi_serial[4]);
scsi_serial[4+scsi_serial[3]]='\0';
trim(&scsi_serial[4]);
sprintf(outStr,"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?> \n<!DOCTYPE properties SYSTEM \"http://java.sun.com/dtd/properties.dtd\"> \n<properties>\n<comment/>\n<entry key=\"SerialNo\">%s</entry>\n</properties>\n", (char *) & scsi_serial[4]);
//strcat((char *)argv[2],(char *)"/hdd.xml");
printf("\n%s",outStr);
// printf("\n%s",(char *)argv[2]);
//storeData((char *)argv[1],(char *) outStr);
}
close(fd);
}else{
printf("\nInsufficient no of arguments \n");
}
return (EXIT_SUCCESS);
}