Re: Examples of kfilter_register(9)?

[Hubert Feyrer <hubert%feyrer.de@localhost>]

On Mon, 31 Aug 2009, Marc Tooley wrote:
> monkey around with it in userspace, but I'm still interested in seeing
> an example, or hearing a description of what it was designed to do and
> what purpose it was designed to serve.

Unless I'm totally off-track here, there is a userland interface: The code 
below watches a given directory, and if any file is written or linked to 
it runs a given command. Maybe that helps... based on code by someone 
elase (I forgot who... sorry! :).


 - Hubert

#include <stdio.h>
#include <sys/event.h>
#include <sys/time.h>
#include <assert.h>
#include <fcntl.h>
#include <stdlib.h>

void usage(void)
{
    printf("Usage: %s dir-to-monitor logfile\n",
           getprogname());
    exit (0);
}

int main(int argc, char *argv[])
{
    char cmd[256];
    int qd, fd;
    struct kevent filter, result;
    int n;

    if (argc != 3)
        usage();

    sprintf(cmd, "( date ; ls -l '%s' ) >%s", argv[1], argv[2]);

    qd = kqueue();
    assert(qd > 0);

    fd = open(argv[1], O_RDONLY);
    assert(fd > 0);

    EV_SET( &filter, fd, EVFILT_VNODE, EV_ADD,
        NOTE_WRITE|NOTE_EXTEND|NOTE_LINK, 0, NULL);

    printf("Waiting for %s to get touched...\n", argv[1]);

    /* n = */ kevent(qd, &filter, 1, &result, 1, NULL);
    /* assert(n > 0); *//* speed up! */

    /* should check 'result' here... */

    system(cmd);
    printf("Ran: %s\n", cmd);

    return 0;
}