Re: catastrophe - but how? Aptitude goes mad

[<tomas@tuxteam.de>]

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On Thu, Jun 30, 2016 at 06:57:06PM -0400, Gene Heskett wrote:
> On Thursday 30 June 2016 16:12:46 Henrique de Moraes Holschuh wrote:
> 
> > grep -r Assume-Yes /etc
> 
> 100% missing here, but lemme see what happens when I use the recursive -R 
> since I can't ever recall using the lower case r for recursion.

Kids, read the man pages. It's good for you :-)

(meant, of course, a bit tongue-in-cheek)

(Actually in this case the info page is better, but perhaps too far away
from the comfort zone. Grep's man page is excellent).

I know man pages are sometimes inscrutable, but *this* is the kind of
occassion I always take to learn something: WTF is the difference
between -r and -R?

After doing this a couple of times one gets a better and better mental
map of the documentation.

I freely admit I didn't know, but now I do:

 -R follows (recursively) symbolic links
 -r follows a symbolic link only if it is the top-level argument

But what I wanted to point out is more the "collateral benefit": I am now
more acquainted with the landscape in grep's man page, now I know that little
shed -r next to the tall tree -R, just past the river, --include=GLOB.

And I have paid tribute to the (in the man/info pages) unnamed authors
(but one can find out [1]) who gave me such a little jewel.

> That took at least 3 or 4 minutes to complete, whereas the -r was back in 
> 500 milliseconds or so.

Big -R should take longer if there are any symlinks in /etc pointing to
massive trees elsewhere. That said, do take caching into account. The
first grep will tend to take significantly longer. Here's from my box
(I elided some warnings because as a user I'm not allowed to nose in
every /etc subdirectory

After explicitly flushing caches (echo 3 > /proc/sys/vm/drop_caches):

    tomas@rasputin:~$ time find /etc > /dev/null
    real    0m0.494s
    user    0m0.028s
    sys     0m0.112s

    tomas@rasputin:~$ time find /etc > /dev/null
    real    0m0.023s
    user    0m0.008s
    sys     0m0.016s

That makes for a rough factor of 20 real time. RAM is faster :-)

> The only positive response should be a never mind:
> 
> /etc/httpd/lib/python2.7/dist-packages/aptdaemon/console.py:        if 
> (not apt_pkg.config.find_b("APT::Get::Assume-Yes") and

I agree with your analysis: this seems irrelevant. No fish in
there :-)

Regards
- -- t
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