You can print a human
readable string for error using 'strerror' function.
see -
man strerror
man errno
--
Thanks,
- John
On 08/16/2009 04:09 PM, Manish Katiyar wrote:
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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