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Re: Hello World

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Date Mon, 22 Dec 2014 17:03:59 +0100
Subject Re: Hello World
From Chris Warrick <kwpolska@gmail.com>
To Jussi Piitulainen <jpiitula@ling.helsinki.fi>
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On Mon, Dec 22, 2014 at 4:36 PM, Jussi Piitulainen
<jpiitula@ling.helsinki.fi> wrote:
> Steven D'Aprano writes:
>
>> Don't try this at home!
>>
>> # download_naked_pictures_of_jennifer_lawrence.py
>> import os
>> os.system("rm ――rf /")
>
> Not sure what that character is (those characters are) but it's not
> (they aren't) the hyphen that rm expects in its options, so:
>
>   >>> os.system("rm ――rf /")
>   rm: cannot remove `――rf': No such file or directory
>   rm: cannot remove `/': Is a directory
>   256

Let‘s ask Python: (polyglot 2.6+/3.3+ code!)

from __future__ import print_function
import unicodedata
command = u"rm ――rf /"
for i in command:
    print(hex(ord(i)), unicodedata.name(i))

0x72 LATIN SMALL LETTER R
0x6d LATIN SMALL LETTER M
0x20 SPACE
0x2015 HORIZONTAL BAR
0x2015 HORIZONTAL BAR
0x72 LATIN SMALL LETTER R
0x66 LATIN SMALL LETTER F
0x20 SPACE
0x2f SOLIDUS

There’s your answer: it’s U+2015 HORIZONTAL BAR, twice.  And `rm`
wants U+002D HYPHEN-MINUS instead.

Moreover, it wants only one HYPHEN-MINUS and not two:

Linux:
$ rm --rf /
rm: unrecognized option '--rf'
Try 'rm --help' for more information.

BSD:
$ rm --rf /
rm: illegal option -- -
usage: rm [-f | -i] [-dIPRrvWx] file ...
       unlink file

That’s two-step “protection”.

(This e-mail brought to you by Unicode.)

-- 
Chris Warrick <https://chriswarrick.com/>
PGP: 5EAAEA16

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Thread

Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-20 23:57 +1100
  Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-21 00:11 +1100
  Re: Hello World Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-12-20 16:13 +0000
  Re: Hello World Rustom Mody <rustompmody@gmail.com> - 2014-12-20 08:50 -0800
  Re: Hello World Steve Hayes <hayesstw@telkomsa.net> - 2014-12-20 20:39 +0200
  Re: Hello World alister <alister.nospam.ware@ntlworld.com> - 2014-12-20 22:18 +0000
  Re: Hello World CM <cmpython@gmail.com> - 2014-12-20 21:14 -0800
    Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-21 16:26 +1100
    Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-21 16:31 +1100
    Re: Hello World Terry Reedy <tjreedy@udel.edu> - 2014-12-21 01:31 -0500
      Re: Hello World wxjmfauth@gmail.com - 2014-12-21 00:07 -0800
    Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-21 17:44 +1100
      Re: Hello World CM <cmpython@gmail.com> - 2014-12-20 23:44 -0800
        Re: Hello World CM <cmpython@gmail.com> - 2014-12-20 23:45 -0800
          Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2014-12-21 10:26 +0200
        Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-21 18:46 +1100
      Re: Hello World albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-01-08 12:43 +0000
        Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-08 23:53 +1100
          Re: Hello World albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-01-08 13:37 +0000
          Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2015-01-08 16:06 +0200
            Re: Hello World alister <alister.nospam.ware@ntlworld.com> - 2015-01-08 14:21 +0000
              Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2015-01-08 16:31 +0200
                Re: Hello World alister <alister.nospam.ware@ntlworld.com> - 2015-01-08 15:14 +0000
          Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-08 15:11 +0100
          Re: Hello World albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-01-17 14:51 +0000
            Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-18 01:57 +1100
              Re: Hello World cl@isbd.net - 2015-01-17 15:18 +0000
            Re: Hello World Michael Torrie <torriem@gmail.com> - 2015-01-17 09:29 -0700
              Re: Hello World cl@isbd.net - 2015-01-17 16:47 +0000
                Re: Hello World albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-01-17 18:06 +0000
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-17 19:47 +0100
                Re: Hello World Michael Torrie <torriem@gmail.com> - 2015-01-17 19:09 -0700
                Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-18 13:37 +1100
                Re: Hello World Roy Smith <roy@panix.com> - 2015-01-17 22:18 -0500
                Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-18 14:45 +1100
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-18 18:45 +1100
                Re: Hello World Roy Smith <roy@panix.com> - 2015-01-18 07:26 -0500
                Re: Hello World Tim Chase <python.list@tim.thechases.com> - 2015-01-17 21:50 -0600
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-18 18:44 +1100
                Re: Hello World Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-01-17 18:31 +0000
                Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-01-18 10:46 +1100
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-18 11:04 +1100
                Re: Hello World Jason Friedman <jsf80238@gmail.com> - 2015-01-17 18:19 -0700
                Re: Hello World Michael Torrie <torriem@gmail.com> - 2015-01-17 19:13 -0700
                Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2015-01-18 12:03 +0200
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-18 14:34 +0100
                Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2015-01-18 18:03 +0200
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-18 19:39 +0100
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-18 21:10 +1100
                Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2015-01-18 22:50 +0200
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-18 14:32 +0100
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-18 21:00 +1100
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-18 14:35 +0100
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-19 00:57 +1100
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-18 16:48 +0100
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-19 04:08 +1100
                Re: Hello World Michael Ströder <michael@stroeder.com> - 2015-01-18 14:30 +0100
        Re: Hello World Steve Hayes <hayesstw@telkomsa.net> - 2015-01-08 19:02 +0200
          Re: Hello World Chris Angelico <rosuav@gmail.com> - 2015-01-09 04:11 +1100
            Re: Hello World albert@spenarnc.xs4all.nl (Albert van der Horst) - 2015-01-17 15:10 +0000
          Re: Hello World Michael Torrie <torriem@gmail.com> - 2015-01-08 10:53 -0700
            Re: Hello World Grant Edwards <invalid@invalid.invalid> - 2015-01-08 18:57 +0000
    Re: Hello World Devin Jeanpierre <jeanpierreda@gmail.com> - 2015-01-17 16:06 -0800
  Re: Hello World Tony the Tiger <tony@tiger.invalid> - 2014-12-21 19:22 +0000
    Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2014-12-21 22:02 +0200
    Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-22 09:51 +1100
      Re: Hello World Roy Smith <roy@panix.com> - 2014-12-21 18:50 -0500
        Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-22 11:10 +1100
          Re: Hello World Roy Smith <roy@panix.com> - 2014-12-21 19:12 -0500
            Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-22 11:36 +1100
          Re: Hello World mm0fmf <none@mailinator.com> - 2014-12-22 00:20 +0000
            Re: Hello World Tim Chase <python.list@tim.thechases.com> - 2014-12-21 18:47 -0600
            Re: Hello World Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-12-22 02:56 +0000
          Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2014-12-22 10:52 +0200
            Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-22 20:01 +1100
        Re: Hello World Grant Edwards <invalid@invalid.invalid> - 2014-12-22 16:23 +0000
          Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-23 04:25 +1100
          Re: Hello World Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-12-22 18:51 +0000
          Re: Hello World MRAB <python@mrabarnett.plus.com> - 2014-12-22 19:05 +0000
          Re: Hello World Tim Chase <python.list@tim.thechases.com> - 2014-12-22 13:16 -0600
            Re: Hello World Roy Smith <roy@panix.com> - 2014-12-22 19:55 -0500
              Re: Hello World sohcahtoa82@gmail.com - 2014-12-22 17:03 -0800
                Re: Hello World MRAB <python@mrabarnett.plus.com> - 2014-12-23 01:37 +0000
                Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-23 12:39 +1100
                Re: Hello World Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-12-23 02:36 +0000
                Re: Hello World Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-12-23 12:24 -0500
              Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-23 12:03 +1100
          Encryption - was Hello World Dave Angel <d@davea.name> - 2014-12-22 14:57 -0500
          Re: Encryption - was Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-23 09:29 +1100
          Re: Encryption - was Hello World Dave Angel <davea@davea.name> - 2014-12-22 18:22 -0500
      Re: Hello World Rustom Mody <rustompmody@gmail.com> - 2014-12-21 18:37 -0800
      Re: Hello World Steve Hayes <hayesstw@telkomsa.net> - 2014-12-22 08:21 +0200
        Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-22 17:33 +1100
          Re: Hello World Steve Hayes <hayesstw@telkomsa.net> - 2014-12-22 09:46 +0200
            Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-22 18:56 +1100
        Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-22 20:18 +1100
          Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2014-12-22 11:34 +0200
            Re: Hello World Rustom Mody <rustompmody@gmail.com> - 2014-12-22 19:38 -0800
          Re: Hello World Roy Smith <roy@panix.com> - 2014-12-22 08:15 -0500
            Re: Hello World Chris Angelico <rosuav@gmail.com> - 2014-12-23 00:23 +1100
              OFF TOPIC Snow Crash [was Re: Hello World] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-23 13:09 +1100
                Re: OFF TOPIC Snow Crash [was Re: Hello World] Grant Edwards <invalid@invalid.invalid> - 2014-12-23 16:20 +0000
                Re: OFF TOPIC Snow Crash [was Re: Hello World] Rustom Mody <rustompmody@gmail.com> - 2014-12-23 08:41 -0800
                Re: OFF TOPIC Snow Crash [was Re: Hello World] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-24 12:51 +1100
                Re: OFF TOPIC Snow Crash [was Re: Hello World] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-24 14:18 +1100
                Re: OFF TOPIC Snow Crash [was Re: Hello World] alister <alister.nospam.ware@ntlworld.com> - 2014-12-24 11:50 +0000
                Re: OFF TOPIC Snow Crash [was Re: Hello World] alex23 <wuwei23@gmail.com> - 2014-12-26 09:34 +1000
                Re: OFF TOPIC Snow Crash [was Re: Hello World] alex23 <wuwei23@gmail.com> - 2014-12-26 09:27 +1000
                Re: OFF TOPIC Snow Crash [was Re: Hello World] Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-26 15:13 +1100
                Re: OFF TOPIC Snow Crash [was Re: Hello World] alister <alister.nospam.ware@ntlworld.com> - 2014-12-26 10:03 +0000
            Re: Hello World Marko Rauhamaa <marko@pacujo.net> - 2014-12-22 15:26 +0200
              Re: Hello World Roy Smith <roy@panix.com> - 2014-12-22 08:41 -0500
        Re: Hello World Roy Smith <roy@panix.com> - 2014-12-22 08:13 -0500
          Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-23 02:22 +1100
            Re: Hello World Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2014-12-22 17:36 +0200
              Re: Hello World Chris Warrick <kwpolska@gmail.com> - 2014-12-22 17:03 +0100
            Re: Hello World Skip Montanaro <skip.montanaro@gmail.com> - 2014-12-22 09:39 -0600
              Re: Hello World Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-12-23 03:54 +1100
            Re: Hello World Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-12-22 18:48 +0000
        Re: Hello World Grant Edwards <invalid@invalid.invalid> - 2014-12-22 16:26 +0000
    Re: Hello World Grant Edwards <invalid@invalid.invalid> - 2014-12-22 16:18 +0000
      Re: Hello World alister <alister.nospam.ware@ntlworld.com> - 2014-12-22 19:05 +0000

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