Re: lseek on /proc/kmsg

[linux-os]

On Wed, 23 Mar 2005, Jan Engelhardt wrote:

> 1> Sure, read() needs to be modified to respect the file-position
> 1> set by kmsg_seek(). I don't think you can get away with the
> 1> call back into do_syslog.
>
> 2>I'm not sure that seek makes any sense on that, since it is more like a
> 2>pipe than a normal file..
>
> Well, seek(fd, 0, SEEK_END) could be used to flush a pipe's buffers.

Yep. That's what I tried to do. Just returns 0 and continues to
contain all the cached data.


> 0>> +static loff_t kmsg_seek(struct file *filp, loff_t offset, int origin) {
> 0>> +    if(origin != 2 /* SEEK_END */ || offset < 0) { return -ESPIPE; }
> 3> "Allow" seeking past the end of the buffer?
>
> Well, what does lseek(fd, >0, SEEK_END) do on normal files?

Goes to the end plus offset. A subsequent read returns EOF
or 0 depending upon your read mechanism. This is what I wanted
to do but with no offset.

Currently, I do this crap:

    for(;;)
    {
        pfd.fd      = ifd;
        pfd.events  = POLLIN;
        pfd.revents = 0;
        if(poll(&pfd, 1, 0) <= 0)
            break;
        (void)read(ifd, ibuf, BUF_LEN);
    }

I should be able to just lseek(ifd, 0 SEEK_END);

> --

Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
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