Re: channel_poll() is blocking

[Aris Adamantiadis <aris@xxxxxxxxxxxx>]

Hi Thomas,

I discourage you to use channel_read_buffer as this function will be
deprecated soon. Please use channel_read instead.

Your example is blocking because you're looping several time inside the
loop. When there is no new data to read, channel_poll returns 0. That
means that you're doing a channel_read when there's nothing to read,
hence the blocking behaviour.

I recommend this rewrite:

     while (channel_poll(channel, 0) > 0)
     {
         char buf[128];
         rc = channel_read_buffer(channel, buf, sizeof(buf), 0);
 	 if(rc<sizeof(buf))
          buf[rc]='\0'; // 0-ends the string
         else
          buf[sizeof(buf)-1]='\0';
         if  (rc < 0)
         {
             channel_close(channel);
             ssh_disconnect(session);
             ssh_finalize();
             return 1;
         }

         printf("%s\n", buf);
     }
 }

Regards,

Aris
Bart Simpson a écrit :
> Hello,
> I wrote a little test program to exec a command on a remote host and
> read the result from channel.
> Open session, authentification with public keys, exec command, etc. work
> all fine.
> But when I try to read something from the channel with this code part
> from the examples of libssh,
> the function channel_poll() is blocking. After a few minutes -1 returned.
> 
> Do anyone know, whats wrong?
> 
> ...
> if  (channel_is_open(channel))
> {
>     while (channel_poll(channel, 0) >= 0)
>     {
>         buf = buffer_new();
>         rc = channel_read_buffer(channel, buf, 0, 0);
> 
>         if  (rc < 0)
>         {
>             buffer_free(buf);
>             channel_close(channel);
>             ssh_disconnect(session);
>             ssh_finalize();
>             return 1;
>         }
> 
>         printf("%s\n", (char *) buffer_get(buf));
>         buffer_free(buf);
>     }
> }
> ...
> 
> 
> Regards,
> Thomas
>