On Tue, Mar 29, 2005 at 03:54:13PM +0530, Mandeep Sandhu wrote:
> On Tue, 2005-03-29 at 15:05 +0530, Gaurav Dhiman wrote:
> > can you paste your strace results ?
> > that might be of some help.
> right, i forgot........here it is
>
> NOTE: the "hello" getting printed in the length arg of
> write is (I think!) the hello that cat wants to print!
[...]
> open("/dev/mydevice", O_RDONLY|O_LARGEFILE) = 3
> fstat64(3, {st_mode=S_IFCHR|0644, st_rdev=makedev(254, 0), ...}) = 0
> open("/dev/mydevice", O_RDONLY|O_LARGEFILE) = 3
> fstat64(3, {st_mode=S_IFCHR|0644, st_rdev=makedev(254, 0), ...}) = 0
> read(3, "hello\0", 4096) = 6
Literial \0 after the string, so string is too long.
> write(1, "hello\0", 6hello) = 6
\0 also gets printed by cat. I don't know what the terminal does with a
\0, but it can be weird things.
> read(3, "", 4096) = 0
> close(3) = 0
> _exit(0) = ?
> [root@nellai root]#
>
>
>
> and here's the read method.......
>
> const char msg[] = "hello";
>
> static ssize_t Device_read(struct file *filp,char *buf,size_t
> count,loff_t *offset)
> {
> if (*offset >= sizeof(msg) )
> {
> return 0;
> }
>
> count = sizeof(msg);
Here's your error, that should be count = strlen(msg);
Erik
--
Erik Mouw
J.A.K.Mouw@xxxxxxxxxxxxxx mouw@xxxxxxxxxxxx
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