Re: Writing bytes to stdout reverses the bytes
On 2018-08-20 17:07, Akkana Peck wrote:
>> Thomas Jollans :
>>> Wonderful. Now why don't we all forget about hexdump and use xxd? ;-)
>
> Marko Rauhamaa writes:
>> Fedora:
>>
>>$ xxd
>>bash: xxd: command not found
>>$ hd
>>bash: hd: command not found
>>$ od -Ax -tx1z -v <<>00 68 65 6c 6c 6f 0a>hello.<
>>06
>
> Or, since this is Python, why be frustrated over imperfect command
> output when you can write something that gives whatever format you
> like best? Long ago the old Unix od used to give something like this,
> and when I was learning Python writing it seemed like a good exercise:
>
> $ bdump hello
> >hello.< ^J
> 20 3e 68 65 6c 6c 6f 2e 3ca
> 32 62 104 101 108 108 111 46 60 10
>
> https://github.com/akkana/scripts/blob/master/bdump
>
> ...Akkana
>
This feels like to could be a one-liner... (different output to yours)
python3 -c 'W = 16; import sys, itertools as it; sum(print("
".join(map("{:02x}".format, b))) or 0 for b in it.takewhile(bool,
map(sys.stdin.buffer.read, it.repeat(W'
or, with offset numbers and an ASCII column,
python3 -c 'W = 16; import sys, itertools as it; sum(print(f"{W*i:08X}
", " ".join(map("{:02x}".format, bb)).ljust(3*W+1), "".join(chr(b) if
0x20 <= b <= 0x7e else "." for b in bb)) or 0 for i, bb in
enumerate(it.takewhile(bool, map(sys.stdin.buffer.read, it.repeat(W)'
--
https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
> Thomas Jollans : > > Wonderful. Now why don't we all forget about hexdump and use xxd? ;-) Marko Rauhamaa writes: > Fedora: > >$ xxd >bash: xxd: command not found >$ hd >bash: hd: command not found >$ od -Ax -tx1z -v <<00 68 65 6c 6c 6f 0a>hello.< >06 Or, since this is Python, why be frustrated over imperfect command output when you can write something that gives whatever format you like best? Long ago the old Unix od used to give something like this, and when I was learning Python writing it seemed like a good exercise: $ bdump hello >hello.< ^J 20 3e 68 65 6c 6c 6f 2e 3ca 32 62 104 101 108 108 111 46 60 10 https://github.com/akkana/scripts/blob/master/bdump ...Akkana -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On 2018-08-20, Chris Angelico wrote: > On Mon, Aug 20, 2018 at 12:01 PM, Grant Edwards >> What do you mean "run it as hd"? >> [... Calling via 'hd' alias makes no difference ...] > Your system is different from mine, then. No doubt. :) > rosuav@sikorsky:~$ ls -l $(which hd) > lrwxrwxrwx 1 root root 7 Apr 12 2017 /usr/bin/hd -> hexdump > rosuav@sikorsky:~$ ls -l $(which hexdump) > -rwxr-xr-x 1 root root 27248 Apr 12 2017 /usr/bin/hexdump > > In 'man hexdump', the -C option says: > -C Canonical hex+ASCII display. Display the input offset in hexa‐ > decimal, followed by sixteen space-separated, two column, hexa‐ > decimal bytes, followed by the same sixteen bytes in %_p format > enclosed in ``|'' characters. > > Calling the command hd implies this option. $ hexdump --version hexdump from util-linux 2.32 In 'man hexdump', the -C option says the exact same thing, but without that last sentence. The 'hd' alias implying -C seems to be a BSD thing. It's not mentioned in the official Linux hexdump man page: https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/tree/text-utils/hexdump.1 But this page does mention 'hd': https://www.freebsd.org/cgi/man.cgi?query=hexdump=1 -- Grant Edwards grant.b.edwardsYow! I just forgot my whole at philosophy of life!!! gmail.com -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
Thomas Jollans : > On 2018-08-20 04:22, Chris Angelico wrote: >> On Mon, Aug 20, 2018 at 12:01 PM, Grant Edwards >> wrote: >>> On 2018-08-20, Ben Bacarisse wrote: It is if you run it as hd. >>> What do you mean "run it as hd"? >>> I don't have an "hd" in my path. >> Your system is different from mine, then. > Wonderful. Now why don't we all forget about hexdump and use xxd? ;-) > > FWIW, I have an Ubuntu system with hd, and an SL7 system without. Fedora: $ xxd bash: xxd: command not found $ hd bash: hd: command not found $ od -Ax -tx1z -v <
Re: Writing bytes to stdout reverses the bytes
On 2018-08-20 04:22, Chris Angelico wrote: > On Mon, Aug 20, 2018 at 12:01 PM, Grant Edwards > wrote: >> On 2018-08-20, Ben Bacarisse wrote: >>> It is if you run it as hd. >> >> What do you mean "run it as hd"? >> >> I don't have an "hd" in my path. > > Your system is different from mine, then. Wonderful. Now why don't we all forget about hexdump and use xxd? ;-) FWIW, I have an Ubuntu system with hd, and an SL7 system without. -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On Mon, Aug 20, 2018 at 12:01 PM, Grant Edwards wrote: > On 2018-08-20, Ben Bacarisse wrote: >> Grant Edwards writes: >> >>> On 2018-08-20, Steven D'Aprano wrote: On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: > When I write bytes to stdout, why are they reversed? Answer: they aren't, use hexdump -C. >>> >>> One might think that dumping out bytes in the correct order ought to >>> be the default format for hexdump. >> >> It is if you run it as hd. > > What do you mean "run it as hd"? > > I don't see any mention of it the hexdump manpage, and I don't have an > "hd" in my path. Some commands alter their behavior based on argv[0], > so I created an alias named "hd" that points to hexdump, but that > doesn't do anything any different than "hexdump": > > $ which hexdump > /usr/bin/hexdump > > $ ls -l $(which hd) > lrwxrwxrwx 1 grante users 16 Aug 19 21:00 /home/grante/bin/hd -> > /usr/bin/hexdump > > $ hd .bashrc | head -n2 > 000 2023 652f 6374 732f 656b 2f6c 622e 7361 > 010 7268 0a63 0a23 2023 6854 7369 6620 6c69 > > $ hexdump .bashrc | head -n2 > 000 2023 652f 6374 732f 656b 2f6c 622e 7361 > 010 7268 0a63 0a23 2023 6854 7369 6620 6c69 > Your system is different from mine, then. rosuav@sikorsky:~$ ls -l $(which hd) lrwxrwxrwx 1 root root 7 Apr 12 2017 /usr/bin/hd -> hexdump rosuav@sikorsky:~$ ls -l $(which hexdump) -rwxr-xr-x 1 root root 27248 Apr 12 2017 /usr/bin/hexdump In 'man hexdump', the -C option says: -C Canonical hex+ASCII display. Display the input offset in hexa‐ decimal, followed by sixteen space-separated, two column, hexa‐ decimal bytes, followed by the same sixteen bytes in %_p format enclosed in ``|'' characters. Calling the command hd implies this option. I'm on Debian GNU/Linux, and the 'hexdump' command comes from a package called bsdmainutils. What are you on, and where is your hexdump from? ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On 2018-08-20, Ben Bacarisse wrote: > Grant Edwards writes: > >> On 2018-08-20, Steven D'Aprano wrote: >>> On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: >>> When I write bytes to stdout, why are they reversed? >>> >>> Answer: they aren't, use hexdump -C. >> >> One might think that dumping out bytes in the correct order ought to >> be the default format for hexdump. > > It is if you run it as hd. What do you mean "run it as hd"? I don't see any mention of it the hexdump manpage, and I don't have an "hd" in my path. Some commands alter their behavior based on argv[0], so I created an alias named "hd" that points to hexdump, but that doesn't do anything any different than "hexdump": $ which hexdump /usr/bin/hexdump $ ls -l $(which hd) lrwxrwxrwx 1 grante users 16 Aug 19 21:00 /home/grante/bin/hd -> /usr/bin/hexdump $ hd .bashrc | head -n2 000 2023 652f 6374 732f 656b 2f6c 622e 7361 010 7268 0a63 0a23 2023 6854 7369 6620 6c69 $ hexdump .bashrc | head -n2 000 2023 652f 6374 732f 656b 2f6c 622e 7361 010 7268 0a63 0a23 2023 6854 7369 6620 6c69 -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On Mon, Aug 20, 2018 at 11:31 AM, Grant Edwards wrote: > On 2018-08-20, Chris Angelico wrote: >> On Mon, Aug 20, 2018 at 11:12 AM, Grant Edwards >> wrote: >>> On 2018-08-20, Steven D'Aprano wrote: On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: > When I write bytes to stdout, why are they reversed? Answer: they aren't, use hexdump -C. >>> >>> One might think that dumping out bytes in the correct order ought to >>> be the default format for hexdump. Dog only know why the actual >>> default format was chosen. If it was 16-bit values in _octal_ you >>> could at least blame the PDP-11 heritage of Unix... >>> >> >> It's dumping sixteen-bit units in correct order. > > I know. What I don't understand is is why 16-bit units in hex is the > default. 8-bits make sense. 32-bits makes sense. 16-bits in octal > makes sense (at least to those of us who first used Unix on a PDP-11). > Ah, I see what you mean. TBH, I no longer am surprised at weird command defaults; many of them carry long history and sometimes arbitrariness, maintained forever for backward compatibility. In this specific case, I just use 'hd' instead of 'hexdump' - the defaults are more to my liking, and it's shorter to boot. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
Grant Edwards writes: > On 2018-08-20, Steven D'Aprano wrote: >> On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: >> >>> When I write bytes to stdout, why are they reversed? >> >> Answer: they aren't, use hexdump -C. > > One might think that dumping out bytes in the correct order ought to > be the default format for hexdump. It is if you run it as hd. -- Ben. -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On 2018-08-20, Chris Angelico wrote: > On Mon, Aug 20, 2018 at 11:12 AM, Grant Edwards > wrote: >> On 2018-08-20, Steven D'Aprano wrote: >>> On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: >>> When I write bytes to stdout, why are they reversed? >>> >>> Answer: they aren't, use hexdump -C. >> >> One might think that dumping out bytes in the correct order ought to >> be the default format for hexdump. Dog only know why the actual >> default format was chosen. If it was 16-bit values in _octal_ you >> could at least blame the PDP-11 heritage of Unix... >> > > It's dumping sixteen-bit units in correct order. I know. What I don't understand is is why 16-bit units in hex is the default. 8-bits make sense. 32-bits makes sense. 16-bits in octal makes sense (at least to those of us who first used Unix on a PDP-11). -- Grant -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On Mon, Aug 20, 2018 at 11:12 AM, Grant Edwards wrote: > On 2018-08-20, Steven D'Aprano wrote: >> On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: >> >>> When I write bytes to stdout, why are they reversed? >> >> Answer: they aren't, use hexdump -C. > > One might think that dumping out bytes in the correct order ought to > be the default format for hexdump. Dog only know why the actual > default format was chosen. If it was 16-bit values in _octal_ you > could at least blame the PDP-11 heritage of Unix... > It's dumping sixteen-bit units in correct order. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On 2018-08-20, Steven D'Aprano wrote: > On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: > >> When I write bytes to stdout, why are they reversed? > > Answer: they aren't, use hexdump -C. One might think that dumping out bytes in the correct order ought to be the default format for hexdump. Dog only know why the actual default format was chosen. If it was 16-bit values in _octal_ you could at least blame the PDP-11 heritage of Unix... -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On Mon, 20 Aug 2018 00:31:35 +, Steven D'Aprano wrote: > When I write bytes to stdout, why are they reversed? Answer: they aren't, use hexdump -C. Thanks to all replies! -- Steven D'Aprano "Ever since I learned about confirmation bias, I've been seeing it everywhere." -- Jon Ronson -- https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On 20Aug2018 00:31, Steven D'Aprano
wrote:
When I write bytes to stdout, why are they reversed?
[steve@ando ~]$ python2.7 -c "print('\xfd\x84\x04\x08')" | hexdump
000 84fd 0804 000a
005
[steve@ando ~]$ python3.5 -c "import sys; sys.stdout.buffer.write(b'\xfd
\x84\x04\x08\n')" | hexdump
000 84fd 0804 000a
005
They're not. Hexdump is presenting your bytes as little endian 2 byte words. So
your leading 0xfd is the _low_ bytes of the 2 bytes word.
Try "od -c" instead.
Cheers,
Cameron Simpson
--
https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On Mon, Aug 20, 2018 at 10:31 AM, Steven D'Aprano
wrote:
> When I write bytes to stdout, why are they reversed?
>
> [steve@ando ~]$ python2.7 -c "print('\xfd\x84\x04\x08')" | hexdump
> 000 84fd 0804 000a
> 005
>
> [steve@ando ~]$ python3.5 -c "import sys; sys.stdout.buffer.write(b'\xfd
> \x84\x04\x08\n')" | hexdump
> 000 84fd 0804 000a
> 005
They're not. They're being printed out as individual bytes, but then
the hexdump command is looking at little-endian sixteen-bit units. Try
the 'hd' command instead, or use 'hexdump -C'.
ChrisA
--
https://mail.python.org/mailman/listinfo/python-list
Re: Writing bytes to stdout reverses the bytes
On 2018-08-20, Steven D'Aprano wrote:
> When I write bytes to stdout, why are they reversed?
>
> [steve@ando ~]$ python2.7 -c "print('\xfd\x84\x04\x08')" | hexdump
> 000 84fd 0804 000a
> 005
They aren't. You're being fooled by the default output format of
hexdump. By default, it displays data as 16-byte integers in
little-endian. If you want to look at bytes, do this:
$ python2.7 -c "print('\xfd\x84\x04\x08')" | hexdump -C
fd 84 04 08 0a|.|
0005
--
https://mail.python.org/mailman/listinfo/python-list
