On Sun, Aug 16, 2009 at 3:09 PM, loody<miloody@xxxxxxxxx> wrote:
> Dear all:
> I try to open /dev/sda1 with system call, open("/dev/sda1", O_RDONLY).
> But each time it will return negative value, that means fail.
Have you checked for the errno ? I guess it is permission denied.
/home/mkatiyar> dd if=/dev/sda1 of=/dev/zero
dd: opening `/dev/sda1': Permission denied
Thanks -
Manish
> my program is like below:
> (gdb) list
> 1 #include<stdio.h>
> 2 #include<fcntl.h>
> 3 int main(void)
> 4 {
> 5 int fd=0;
> 6 fd = open("/dev/sda1", O_RDONLY);
> 7
> 8 printf("%d\n",fd);
> 9 }
> 10
> (gdb) b 8
> Breakpoint 1 at 0x8048423: file test.c, line 8.
> (gdb) r
> Starting program: /home/cc/a.out
>
> Breakpoint 1, main () at test.c:8
> 8 printf("%d\n",fd);
> (gdb) p fd
> $1 = -1
> (gdb)
>
>
> But I am quite sure I really get /dev/sda1 on my linux system.
> below are the dmesg:
> $ dmesg |grep sda
> [ 4.304624] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012 MB)
> [ 4.304642] sd 0:0:0:0: [sda] Write Protect is off
> [ 4.304646] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
> [ 4.304672] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
> enabled, doesn't support DPO or FUA
> [ 4.304742] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012 MB)
> [ 4.304757] sd 0:0:0:0: [sda] Write Protect is off
> [ 4.304760] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
> [ 4.304786] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
> enabled, doesn't support DPO or FUA
> [ 4.304790] sda:<4>Driver 'sr' needs updating - please use bus_type methods
> [ 4.319499] sda1 sda2 sda3 < sda5<6>usb 4-2: configuration #1
> chosen from 1 choice
> [ 4.359729] sda6 > sda4
> [ 4.359951] sd 0:0:0:0: [sda] Attached SCSI disk
> [ 22.637589] EXT3 FS on sda4, internal journal
> [ 23.586600] EXT3 FS on sda6, internal journal
> $
> Does that mean I use the wrong systemcall or we cannot open /dev/sda1 like this?
> appreciate your help,
> miloody
>
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>
--
Thanks -
Manish
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