[systemd-devel] sd_listen_fds: find file descriptor

[Michael D. Berger]

[...]
> 
> Hmm? You should usually consume all fds you get passed. And 
> if you cannot handle more than one, then exit quickly with an 
> error message. And if any of the fds is invalid, then print 
> an error message and leave, too.
> 
> This is what I'd usually use:
> 
> 
> int fd, n;
> 
> n = sd_listen_fds();
> if (n < 0)  {
>         fprintf(stderr, "sd_listen_fds(): %s\n", strerror(-n));
>         exit(1);
> }
> 
> for (fd = SD_LISTEN_FDS_START; fd < SD_LISTEN_FDS_START + n; fd ++) {
>         if (sd_is_socket_inet(fd, ...) <= 0) {
>                 fprintf(stderr, "Invalid socket passed.\n");
>                 exit(1);
>         }
> 
>         /* do something with the fd... */ }
> 
> (This is for the generic case where the service can handle 
> more than one fd. If you can handle ony one, then check 
> whether n == 1 and if it isn't exit saying you can't deal 
> with more than one fd.)
> 
> Lennart
> 

What you say is clear, but I am perplexed by the fact that
in a case where there will be one handle, that handle will
always be 3.  How do we know that 3 is not being used by
something else?  I thought that the system has to choose
a handle that is available.

Mike.
--
Michael D. Berger
m.d.berger at ieee.org
http://www.rosemike.net/