[erlang-questions] what *exactly* are sname and name ?

Joe Armstrong <>
Sat Dec 9 19:45:54 CET 2006


On 12/9/06, Ulf Wiger <> wrote:
>
> Den 2006-12-09 15:13:23 skrev Joe Armstrong <>:
>
> > Hello,
> >
> > Question - *exactly* what is a "name" and "sname".
> >
> > I do not want to know how to use them (I know)  I want to know what they
> > mean?
> >
> > I'm writing chapters on "distributed erlang".
> >
> > Can anybody complete the sentence(s).
> >
> >       The command line argument  "-sname X" means ...
> >
> >       The command line argument  "-name Y" means....
> >
> >       The difference between sname and name is ...
> >
> >       Thanks
>
> Just to point out the obvious, this is what the 'erl' man page says about
> -name and -sname:


Well it's not obvious to me....


-name Name
> Makes the Erlang runtime system into a distributed node. This flag invokes
> all network servers necessary for a node to become distributed. See
> net_kernel(3). It is also ensured that epmd runs on the current host
> before Erlang is started. See epmd(1).
> The name of the node will be , where Host is the fully qualified
> host name of the current host. For short names, use the -sname flag
> instead.


This seems understandable


-sname Name
> Makes the Erlang runtime system into a distributed node, similar to -name,
> but the host name portion of the node name  will be the short
> name, not fully qualified.This is sometimes the only way to run
> distributed Erlang if the DNS
>
(Domain Name System) is not running. There can be no communication between
> nodes running with the -sname flag and those running with the -name flag,
> as node names must be unique in distributed Erlang systems.


What on earth does this mean - I've read this several times and I don't
understand it.

"the host name portion of the node name  will be the short
name, not fully qualified."

What does this mean????

What It might mean might be the following (at least this would be
logical, but it would mean that the syntactic form of Name in the two
comands was different)

   erl -name 

       makes a node with name 

   erl -sname foo

     when my host name is aaa.bbb.ccc.com
     would create  a node called 

If this were the case then I see no reason why the node started
with name would not be able to talk to the node started with sname
..

    When I do erl -sname foo on my machine (with hostname msi)
erlang says my node is called:

() >

(ie not ) ....

   Goodness knows why

/Joe





--
> Ulf Wiger
>
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