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<milo...@gmail.com> 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 - Manishmy 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 -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecar...@nl.linux.org Please read the FAQ at http://kernelnewbies.org/FAQ
