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

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

Rainer Weikusat <rweikusat@talktalk.net> writes:

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

When I recently inspected an 'strace' log and saw the huge amount
of system-calls done for a simple standard command (like 'rm') -
it's more than a dozen! and most lead just to ENOENT - I wondered
about the default PATH definition which is for my system
  /usr/lib/lightdm/lightdm
  /usr/local/sbin
  /usr/local/bin
  /usr/sbin
  /usr/bin
  /sbin
  /bin
  /usr/games
(here I'm omitting my own additions, '~/bin' and '.', and I separated
them, one on each line for a better visualization of the "problem" or,
maybe better, for the "questions".)
>
The above PATH components are for a terminal running under some
window manager, a plain console window will not show the 'lightdm'
entry (but I rarely work on plain consoles).
>
This raises a few questions, and someone may shed some light on the
rationale for above default settings... (and how to "fix" it best)

>
Why do you want to change that? At worst, this will make seven execve to
execute binary. Usually, it will rather be 4. That's not going to take a
noticeable amount of time.
>
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 ⅕ of the planet and hence, the latencies certainly
ought to be a lot lower.

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.