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Re: Environment Variable weirdness


On Wed, 29 Sep 1999, Salman Ahmed wrote:

> >>>>> "Nathan" == Nathan E Norman <finn@midco.net> writes:
>     Nathan> It's faster to use a "UNIX domain socket" when all traffic is
>     Nathan> local as you avoid some of teh overhead of an IP stack.  Why
>     Nathan> waste those milliseconds?
> Would you be willing to explain the technicalities behind that ? Sounds
> like a neat `optimization'. BTW, is this a Debian-specific feature ? I
> haven't seen this in RedHat.

AFAIK, it's a feature of most modern Unicies. It's not publicized much,
because when it's needed it's just used for the most part. If you do
socket programming, your reference work will probably mention them
(Programming Perl does, for one)

> Now for a networked system, you'd have to change the DISPLAY env var
> to allow remote X clients to display locally, right ?

Technically yes, but not the way you're thinking.

When you connect to a remote machine using telnet, DISPLAY is usually
initially unset (when it's not, it's almost always initialized to the
proper value). So you'd set it manually to point to your machine.

When you connect via SSH with the proper X forwarding options, it'll
automatically set the DISPLAY variable to the proper value to securely
forward the connection. If you change it to what you'd use under telnet,
you'll lose the security. If the machine you're connecting to is named
foobar, the variable will probably look something like 'foobar:10.0'
(instead of 'yourmachine.example.com:0.0' as with telnet)

On your local machine, you'd still use unix domain sockets like you always

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