Re: chmod -R +x for directories only

On Wed, 31 Aug 2005, Big and Blue moaned:
> >Simon Waters wrote:
>
>> Quite, although it does beg the question 'why is the maximum command
>> length still defaults to such a relatively small size?'.
>
> Define "relitively small". It varies between Unices (from 4096
> (according to the header file, but actually much higher) to 262144
> that I've seen), and find/xargs isn't written specifcally for
> Linux.

On many Unixes, environment+command-line must not exceed a (not large)
constant, and GNU findutils works there, too.

e.g. HP-UX 10, where the constant is 24K. (I was working on an HP-UX 10
system once where they had 22K in their enormously bloated environment
--- they hadn't realised there was a limit --- leaving under 2K for
command lines. Bootstrapping GCC there was especially amusing: I had
to hack GNU make to add an xargs builtin to it, and hack GCC's
staging commands to use that builtin, because otherwise the inter-stage
mv overflowed that box's pathetic command line.)

>> When my systems had 17,000 files on it was rarely an issue
>
> Now imagine a use who creates > 300,000 files in *one directory*.
> I don't need to imagine this - I have such users.

INN, mh, GNUS's nnml backend... it's not uncommon. I have one directory
with >500k files in it on this box.

>> I understand why POSIX sets a "minimum maximum" length, but I believe
>> Solaris addressed this already, and introduced a different but much larger
>> arbitrary limit.
>
> Solaris is the 262144 mentioned above (from memory). Part of the
> reason is that the command line (and environment) need to be
> copied into the kernel for an exec()?

Indeed; the initial command-line storage is in the kernel on Solaris and
Linux too. (Linux has a 32 page limit without kernel hacks.)

--
`... published last year in a limited edition... In one of the
great tragedies of publishing, it was not a limited enough edition
and so I have read it.' --- James Nicoll
.

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