From: Oasjxzcoijoasjdflas Asdfizxcv kklas <gorhas@...>
Date: 2009-05-14T01:09:27+09:00
Subject: Re: How Check File Busy?

Greg Willits wrote:
> Hey everyone, thanks for the input.
> 
> My FTP server does indeed support post processing. Should have thought 
> of that. However, I'd rather not couple this particular process to the 
> FTP server if possible.
> 
> I read up on fuser and lsof, and will experiment with those options 
> first.
> 
> I have some options now, so thanks.
> 
> -- gw


You can "easy" write a small C snipplet that checks if something happens 
to a file and then make a ruby-class of this and use it in your ruby 
program.

Here is a sketch...

---<C-program>---

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

#define TMOUT_SEC 2
#define TMOUT_NSEC 0

//**********************************************************************
// This handles events. It blocks on kqueue.
//**********************************************************************
handle_events(int kq )
{

  const struct kevent ch;
  struct kevent ev;
  int nchanges;
  int nevents;
  int error;
  int i;

  int n;
  struct timespec timeout =
    { TMOUT_SEC, TMOUT_NSEC };

  n = kevent(kq, &ch , nchanges,
       &ev, nevents, &timeout );

  if( n <= 0 ) {
    perror(error);    /* what kind of error */
    exit(-1);
  }

  for( i = 0 ; i < n; i++ ) {

    if(ev[i].flag & EV_ERROR)
      exit(-1); /* error */

    if(ev[i].filter == EVFILT_READ)
      readable_fd(ev[i].ident);
    if(ev[i].filter == EVFILT_WRITE)
      writable_fd(ev[i].ident);
  }
}


readable_fd( int fd )
{
  printf("File_fd to read %d\n", fd );
}

writable_fd( int fd )
{
  printf("File_fd to read %d\n", fd );
}


update_fd(int fd, int action,
          int filter )
{

  ch[nchanges].ident = fd;
  ch[nchanges].filger = filter;
  ch[nchanges].flags =
     action == ADD ? EV_ADD
    : EV_DELETE;
  nchanges++;

}


main()
{
  int kq;
  kq = kqueue();
  printf("Start of program\n");
  handel_events( kq );
}

And then you need to make it to a ruby class.

Read in the ruby book how to do this...

---<Ruby class>---

#include "ruby.h"
#include <stdlib.h>

static int id_push;

static VALUE t_init( VALUE self )
{
  ...
}

static VALUE t_notify( VALUE self, VALUE obj )
{
  ...
}

VALUE cTEST;

void Init_my_test(){
   cTEST = rb_define_class("myTest", rb_cObject);
   rb_define_method( cTest, "initialize", t_init, 0);
   rb_define_method( cTest, "notify", t_notify, 1);
   id_push = rb_intern("push");
}

Then compile and use

---<Use in ruby program>---

require 'my_test'

t = MyTest.new

# look for close or write or name change...
while...
   t.notify("filename");



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