Re: Default PATH setting - reduce to something more sensible?

scott@slp53.sl.home (Scott Lurndal) writes:

Rainer Weikusat <rweikusat@talktalk.net> writes:

scott@slp53.sl.home (Scott Lurndal) writes:

Rainer Weikusat <rweikusat@talktalk.net> writes:

Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:

[...]

As far as I could determine, some sort of path searching has existed
since the 6th edition of UNIX (., /bin and /usr/bin hardcoded in the
shell) and in its present form, it has existed since the 7th edition of
UNIX. Which means PATH searching was used on PDP-11 16-bit minicomputers
in the 1970s. It didn't cause performance problems back
then and will thus certainly don't cause any today.

>
There are cases where it _does_ cause performance degradation, if one or
more of the PATH elements refer to NFS filesystems, for example.

>
The internet RTT from Reading/ UK to Dallas/ Texas is about
0.12s. That's fast enough that there's no noticeable latency in
interactive shell sessions. I doubt that many real-world NFS
installations span â…• of the planet and hence, the latencies certainly
ought to be a lot lower.

>
You seem to have have forgotten that the NFS server needs to
do a directory lookup on the file server, which adds to the R/T
latency, sometimes significantly on a busy filesystem.

Well, then, which is it? Local file system operations or network
latencies? Local file system operations on a NFS server are no different
from local file system operations on some other multi-user machine, eg,
the abovementioned PDP-11.

[...]

I'm growing a bit allergic to NFS as universal example of deviant
behaviour --- that's a problem of NFS and not of code innocently and
unknowingly making use of it.

>
It is something that people run into every day in the real world.

Maybe they do. But certainly not on Linux installations using only local
file systems. I'm also (barely) old enough to remember DCE clusters
based on DEC servers using AFS/ NFS to provide "home directories" and
"software" to diskless workstations and to know how real-world PATHs of
traditional UNIX installation used to look like, basically, every
software package installed into its own hierarchy and all glued together
with PATH into a seamless whole. These PATHs used to have a lot more
than just seven elements. I don't remember latencies being a particular
problem in this enivronment¹.

¹ A whose class B in a single, happy, broadcast domain and using
shared-medium yellowcable and even older  technologies in the more
outlying areas