pvaneynd

20 years of UNICODE for the win?

Thu, 30 Mar 2017 07:19:10 GMT

As some of you know I'm back to coding. This morning I was trying to create a SQL table which failed with mysterious errors, like:

DB=> CREATE TABLE sequence ( sequence_id INTEGER NOT NULL, guid_id INTEGER REFERENCES public.guid(id), sequence_number INTEGER NOT NULL); ERROR: relation "public.guid" does not exist Time: 3.007 ms DB=> \dt guid List of relations Schema | Name | Type | Owner --------+------+-------+---------- public | guid | table | pevaneyn (1 row)

I was suspecting a hidden character, so od to the rescue:

$ od -c failing-command ... 0000140 i d I N T E G E R R E F E R 0000160 E N C E S 357 273 277 g u i d ( i d ...

Octal 357 273 277? Clearly this is UTF-8 encoding of something invisible. Let's use clisp:

[1]> CUSTOM:*TERMINAL-ENCODING* #<ENCODING CHARSET:UTF-8 :UNIX> [2]> (EXT:CONVERT-STRING-FROM-BYTES (vector #o357 #o273 #o277) CUSTOM:*TERMINAL-ENCODING*) "" [3]> (aref (EXT:CONVERT-STRING-FROM-BYTES (vector #o357 #o273 #o277) CUSTOM:*TERMINAL-ENCODING*) 0) #\ZERO_WIDTH_NO-BREAK_SPACE Ok an invisible space got inserted somewhere along the line... At least I'm not getting mad and forgetting basic SQL :)

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waisting some CPU time

Fri, 23 Oct 2015 04:30:10 GMT

Given some people having rainbow tables I'm now waisting a lot of cpu time doing: for i in 2046 3072 4096 6144 7680 8192 ; do ssh-keygen -G moduli-$i.candidates -b $i ssh-keygen -T moduli-$i -f moduli-$i.candidates done mv /etc/ssh/moduli /etc/ssh/moduli-normal cat moduli-[23478]* > /etc/ssh/moduli systemctl restart ssh.service This should give me brand-new primes, used only by me. So even if 'bad people' spend a lot of time and money hacking the 20 odd 2048-bit primes distributed with ssh, I would be ... higher on their target list?

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A tale of four disks

Fri, 04 Jul 2014 07:04:19 GMT

A had a long string of problems with our server at home... ( Read more... )

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Finding a new line in a file

Fri, 18 Apr 2014 12:41:36 GMT

Today I helped a collegue who came with the question: I have two files, how do I find which lines were added to one file, but not to the other?

He was thinking of a program to write. I'm more a KISS person, why waste time writing a program when brute force will do just fine.

So:

We have two files a and b:

pevaneyn@mac-book:/tmp :) $ cat a 1 2 3 4 5 pevaneyn@mac-book:/tmp :) $ cat b 1 2 3 4 5 7 8

We want to see the lines in b which are not in a:

pevaneyn@mac-book:/tmp :) $ cat a b | sort | uniq -u 7 8

So we take the two files, sort then and then print the unique lines.

But what if there are also unique lines in a which we don't need? So let's add a line to 0 which we do not want to see in the output:

pevaneyn@mac-book:/tmp :) $ cat >> a 0 pevaneyn@Pmac-book:/tmp :) $ cat a b | sort | uniq -u 0 7 8

How do we remove this 0?

A trick is to include a twice, then a line in a will never be unique:

pevaneyn@mac-book:/tmp :) $ cat a a b | sort | uniq -u 7 8

I used a similar method today to find which interface gave the CRC errors...

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Old versus new

Mon, 07 Apr 2014 06:49:41 GMT

For a side project at $WORK I need to plot some data.

In the past I used gnuplot but as I wanted to interactively investigate the data I wrote a GUI browser in Clojure. This was relatively easy and fast enough.

But I've been told that I'm not with the new hotness and that I should investigate doing this in the browser. So I found the pretty impressive dygraphs javascript library.

The plots look fantastic and are really what I need. So I make my first html5 like page and tried it.

At first I thought that something was wrong. If I do this plot with gnuplot I get:

$ time gnuplot plot.gnuplot real 0m0.818s user 0m0.608s sys 0m0.209s

In Safari it took 22 minutes, while showing a beachball all the time, to plot this data. Chrome and Firefox do it quite a bit better at only two minutes, but still... not subsecond is it? Using the 'canvas' html5 terminal in gnuplot produces 14M html file which only takes something lik 20 seconds to get drawn in all browsers.

But I must admit that the default look and interactivity of dygraph is lightyears ahead of my gnuplot settings...

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IPv6 versus IPv4 at fosdem :S

Sat, 04 Feb 2012 16:13:17 GMT

how so?

pevaneyn-mac:wireshark pevaneyn$ traceroute v4.fr.ipv6-test.com traceroute to v4.fr.ipv6-test.com (46.105.61.149), 64 hops max, 52 byte packets 1 193.191.79.254 (193.191.79.254) 6.215 ms 0.282 ms 0.244 ms 2 ge.ar1.brucam.belnet.net (193.191.4.49) 0.350 ms 0.325 ms 0.365 ms 3 10ge.cr2.bruvil.belnet.net (193.191.16.189) 1.143 ms 0.964 ms 0.994 ms 4 ovh.bnix.net (194.53.172.70) 2.396 ms 1.900 ms 1.942 ms 5 rbx-g2-a9.fr.eu (94.23.122.137) 5.712 ms 4.725 ms 4.794 ms 6 rbx-2-6k.fr.eu (91.121.131.9) 10.489 ms 15.149 ms rbx-1-6k.fr.eu (91.121.131.13) 50.591 ms 7 rbx-26-m1.fr.eu (213.251.191.201) 4.448 ms rbx-26-m1.routers.ovh.net (213.251.191.73) 4.754 ms 4.996 ms 8 eight.t0x.net (46.105.61.149) 3.950 ms 3.975 ms 4.067 ms pevaneyn-mac:wireshark pevaneyn$ traceroute6 v6.fr.ipv6-test.com traceroute6 to v6.fr.ipv6-test.com (2001:41d0:1:d87c::7e57:1) from 2001:6a8:1100:beef:114f:fb76:XXXX:XXXX, 64 hops max, 12 byte packets 1 2001:6a8:1100:beef::1 0.558 ms 0.674 ms 0.507 ms 2 2001:6a8:1000:800f::1 0.370 ms 0.414 ms 0.393 ms 3 10ge.cr2.bruvil.belnet.net 1.106 ms 1.112 ms 1.034 ms 4 ae0-200.bru20.ip6.tinet.net 1.620 ms 1.572 ms 1.523 ms 5 xe-2-1-0.ams20.ip6.tinet.net 6.063 ms xe-5-2-0.ams20.ip6.tinet.net 5.999 ms xe-8-1-0.ams20.ip6.tinet.net 6.002 ms 6 * * * 7 * * * 8 * * * 9 fra-5-6k.de.eu 25.602 ms * 30.531 ms 10 rbx-g2-a9.fr.eu 31.890 ms 27.448 ms 26.656 ms 11 rbx-1-6k.fr.eu 29.996 ms rbx-2-6k.fr.eu 33.715 ms rbx-1-6k.fr.eu 26.735 ms 12 2001:41d0:1:d87c::7e57:1 25.498 ms 31.873 ms 30.815 ms

So a trip around Europe. But IPv6 needs not be slow:

pevaneyn-mac:fosdem pevaneyn$ traceroute6 www.debian.org traceroute6: Warning: www.debian.org has multiple addresses; using 2001:858:2:2:214:22ff:fe0d:7717 traceroute6 to www.debian.org (2001:858:2:2:214:22ff:fe0d:7717) from 2001:6a8:1100:beef:114f:fb76:XXXX:XXXX, 64 hops max, 12 byte packets 1 2001:6a8:1100:beef::1 0.640 ms 1.731 ms 0.607 ms 2 2001:6a8:1000:800f::1 0.491 ms 0.356 ms 0.387 ms 3 2001:6a8:1000:2::2 0.442 ms 10ge.cr2.bruvil.belnet.net 1.081 ms 0.989 ms 4 10ge.cr1.brueve.belnet.net 1.979 ms 10ge.cr1.brueve.belnet.net 1.718 ms 1.479 ms 5 20gigabitethernet1-3.core1.ams1.ipv6.he.net 4.766 ms 8.460 ms 7.190 ms 6 10gigabitethernet1-1.core1.fra1.he.net 16.977 ms 20.783 ms 11.835 ms 7 ge2-19-decix-ipv6-c1.ix.sil.at 70.823 ms 42.928 ms 45.012 ms 8 2001:858:66:203:215:2cff:fe8d:bc00 27.416 ms 26.934 ms 28.561 ms 9 ip6-te1-4-c2.oe3.sil.at 26.776 ms 26.413 ms 26.856 ms 10 2001:858:66:22c:217:fff:fed4:6000 27.156 ms 27.472 ms 26.778 ms 11 englund.debian.org 27.211 ms 27.641 ms 27.823 ms pevaneyn-mac:fosdem pevaneyn$ traceroute www.debian.org traceroute: Warning: www.debian.org has multiple addresses; using 86.59.118.148 traceroute to www.debian.org (86.59.118.148), 64 hops max, 52 byte packets 1 193.191.79.254 (193.191.79.254) 0.619 ms 0.254 ms 0.255 ms 2 ge.ar1.brucam.belnet.net (193.191.4.49) 0.432 ms 0.385 ms 0.448 ms 3 10ge.cr1.brueve.belnet.net (193.191.16.205) 1.153 ms 1.557 ms 0.951 ms 4 nl-asd-dc2-ias-csg01.nl.kpn.net (195.69.144.144) 5.608 ms 5.442 ms 10.251 ms 5 * * * 6 ffm-s1-rou-1021.de.eurorings.net (134.222.229.10) 38.019 ms 37.926 ms ffm-s1-rou-1021.de.eurorings.net (134.222.231.250) 39.953 ms 7 ffm-s1-rou-1022.de.eurorings.net (134.222.228.86) 40.075 ms ffm-s1-rou-1022.de.eurorings.net (134.222.228.90) 38.180 ms ffm-s1-rou-1022.de.eurorings.net (134.222.228.86) 42.755 ms 8 mchn-s1-rou-1022.de.eurorings.net (134.222.228.194) 33.019 ms 33.211 ms 37.045 ms 9 wien-s2-rou-1002.at.eurorings.net (134.222.228.46) 39.827 ms 37.795 ms 39.839 ms 10 wien-s2-rou-1041.at.eurorings.net (134.222.123.242) 37.581 ms 37.633 ms 39.505 ms 11 sil.cust.at.eurorings.net (134.222.123.150) 37.654 ms 35.650 ms 35.521 ms 12 englund.debian.org (86.59.118.148) 38.009 ms 38.124 ms 40.628 ms

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