On Wed, 27 Jun 2018 10:06:40 -0700
xi wrote:
> > On Jun 25, 2018, at 16:19, Tomasz Rola wrote:
> >
> > On Sun, Jun 24, 2018 at 10:53:37PM -0400, Steve Litt wrote:
> >> On Thu, 21 Jun 2018 00:56:04 +0200
> >> Tomasz Rola wrote:
> >>
> > [...]
> >>> Craps. I have consulted OpenBSD's
> On Jun 25, 2018, at 16:19, Tomasz Rola wrote:
>
> On Sun, Jun 24, 2018 at 10:53:37PM -0400, Steve Litt wrote:
>> On Thu, 21 Jun 2018 00:56:04 +0200
>> Tomasz Rola wrote:
>>
> [...]
>>> Craps. I have consulted OpenBSD's manpage for dd and there is no
>>> mention of iflag. So this will not
Tomasz Rola wrote:
> On Sun, Jun 24, 2018 at 10:53:37PM -0400, Steve Litt wrote:
> > On Thu, 21 Jun 2018 00:56:04 +0200
> > Tomasz Rola wrote:
> >
> [...]
> > > Craps. I have consulted OpenBSD's manpage for dd and there is no
> > > mention of iflag. So this will not work on OpenBSD. I will
On Sun, Jun 24, 2018 at 10:53:37PM -0400, Steve Litt wrote:
> On Thu, 21 Jun 2018 00:56:04 +0200
> Tomasz Rola wrote:
>
[...]
> > Craps. I have consulted OpenBSD's manpage for dd and there is no
> > mention of iflag. So this will not work on OpenBSD. I will have to
> > rethink this, sorry.
> >
On Thu, 21 Jun 2018 00:56:04 +0200
Tomasz Rola wrote:
> On Thu, Jun 21, 2018 at 12:44:14AM +0200, Tomasz Rola wrote:
> [...]
> > => (591 60): cat nread
> > #!/bin/sh
> >
> > # nread n - read up to n bytes from stdio, put them on to stdout
> >
> > N=$1
> >
> > dd bs=512 count=$((N / 512))
On Thu, Jun 21, 2018 at 08:06:46PM +0200, Vincent Legoll wrote:
> Hello,
>
> The man page did not say bs has to be a power of 2.
>
> On a very old macppc openbsd box:
>
> vince@mini:~$ dd count=1 bs=123456789 < /dev/zero > zero.bin
> 1+0 records in
> 1+0 records out
> 123456789 bytes
Hello,
The man page did not say bs has to be a power of 2.
On a very old macppc openbsd box:
vince@mini:~$ dd count=1 bs=123456789 < /dev/zero > zero.bin
1+0 records in
1+0 records out
123456789 bytes transferred in 9.833 secs (12554493 bytes/sec)
On a much more recent core i7 linux:
On Thu, Jun 21, 2018 at 3:15 PM, Daniel Hartmeier wrote:
> I think they meant dd and just didn't care about efficiency:
>
> http://austingroupbugs.net/bug_view_page.php?bug_id=407
Thanks for digging this out!
> Does ghead -c beat a simple buffer loop?
Your head-c.c seems to have the same
On Thu, Jun 21, 2018 at 03:08:10PM +0200, Jan Stary wrote:
> On Jun 20 17:32:51, maxim.pich...@gmail.com wrote:
> > dd bs=1 count=1234567 will copy 1234567 bytes and then stop, but it's slow.
>
> $ dd bs=1 count=1234567 < /dev/zero > /dev/null
> 1234567+0 records in
> 1234567+0 records out
>
On Thu, Jun 21, 2018 at 03:08:10PM +0200, Jan Stary wrote:
> $ dd count=1 bs=1234567 < /dev/zero > /dev/null
> 1+0 records in
> 1+0 records out
> 1234567 bytes transferred in 0.001 secs (653970943 bytes/sec)
That was my first hunch as well, but try
$ printf "foo\nbar\n" | dd count=1
On Thu, Jun 21, 2018 at 10:57:40AM +0200, Maximilian Pichler wrote:
> > dd ibs=1 count=n
>
> Nice, this is about three time as fast as bs=1. Both are much slower
> than 'ghead -c'.
I think they meant dd and just didn't care about efficiency:
On Jun 20 17:32:51, maxim.pich...@gmail.com wrote:
> dd bs=1 count=1234567 will copy 1234567 bytes and then stop, but it's slow.
$ dd bs=1 count=1234567 < /dev/zero > /dev/null
1234567+0 records in
1234567+0 records out
1234567 bytes transferred in 4.507 secs (273886 bytes/sec)
$ dd count=1
On Thu, Jun 21, 2018 at 11:05 AM, Abel Abraham Camarillo Ojeda
wrote:
> $ cat file | perl -ne 'BEGIN { $/ = \1 } print if $. <= 5; exit 0 if $. == 5'
This is much slower than 'dd ibs=1'
On Thu, Jun 21, 2018 at 3:57 AM, Maximilian Pichler
wrote:
> On Thu, Jun 21, 2018 at 9:48 AM, Otto Moerbeek wrote:
>>> On Thu, Jun 21, 2018 at 12:11:52AM +0200, Maximilian Pichler wrote:
>>> > I'm just wondering what these other utilities might be.
>>>
>>> hexdump -v -n 1234567 -e '"%c"'
>
>
On Thu, Jun 21, 2018 at 9:48 AM, Otto Moerbeek wrote:
>> On Thu, Jun 21, 2018 at 12:11:52AM +0200, Maximilian Pichler wrote:
>> > I'm just wondering what these other utilities might be.
>>
>> hexdump -v -n 1234567 -e '"%c"'
Speed-wise this is roughly on par with 'dd bs=1'.
>> If the input
On Thu, Jun 21, 2018 at 07:38:49AM +0200, Daniel Hartmeier wrote:
> On Thu, Jun 21, 2018 at 12:11:52AM +0200, Maximilian Pichler wrote:
>
> > I'm just wondering what these other utilities might be.
>
> hexdump -v -n 1234567 -e '"%c"'
>
> If the input doesn't contain backslashes (or something
On Thu, Jun 21, 2018 at 12:11:52AM +0200, Maximilian Pichler wrote:
> I'm just wondering what these other utilities might be.
hexdump -v -n 1234567 -e '"%c"'
If the input doesn't contain backslashes (or something else, tr(1))
vis -aoF6 | head -n 1234567 | unvis
Daniel
On Thu, Jun 21, 2018 at 12:44:14AM +0200, Tomasz Rola wrote:
[...]
> => (591 60): cat nread
> #!/bin/sh
>
> # nread n - read up to n bytes from stdio, put them on to stdout
>
> N=$1
>
> dd bs=512 count=$((N / 512)) iflag=fullblock 2>/dev/null
> dd bs=1 count=$((N % 512)) iflag=fullblock
On Thu, Jun 21, 2018 at 12:02:14AM +0200, Maximilian Pichler wrote:
> Your script is incorrect.
>
> $ dd if=/dev/zero bs=1 | ./nread 1234567 | wc -c
> 0+2411 records in
> 0+2411 records out
> 2411 bytes transferred in 0.038 secs (62579 bytes/sec)
> 135+0 records in
> 135+0 records out
> 135 bytes
POSIX says
(http://pubs.opengroup.org/onlinepubs/9699919799/utilities/head.html#tag_20_57_18)
about the 'head' utility:
"There is no -c option (as there is in tail) because it is not
historical practice and because other utilities in this volume of
POSIX.1-2017 provide similar functionality."
Your script is incorrect.
$ dd if=/dev/zero bs=1 | ./nread 1234567 | wc -c
0+2411 records in
0+2411 records out
2411 bytes transferred in 0.038 secs (62579 bytes/sec)
135+0 records in
135+0 records out
135 bytes transferred in 0.001 secs (126148 bytes/sec)
2546
$ man dd
...
count=n
On Wed, Jun 20, 2018 at 08:20:16PM +0200, Maximilian Pichler wrote:
> On Wed, Jun 20, 2018 at 7:17 PM, Tomasz Rola wrote:
> > But seriously: man sh.
>
> Are you saying there is a shell built-in that does this? If so, which one?
=> (591 13):cat nread
#!/bin/sh
# nread n - read up to n
On Wed, Jun 20, 2018 at 7:17 PM, Tomasz Rola wrote:
> But seriously: man sh.
Are you saying there is a shell built-in that does this? If so, which one?
On Wed, Jun 20, 2018 at 06:50:06PM +0200, Tomasz Rola wrote:
[...]
>
> Maybe suggest to the teacher that she sticks to numbers divisible by
> 512? That is what haxorz do.
But seriously: man sh.
--
Regards,
Tomasz Rola
--
** A C programmer asked whether computer had Buddha's nature. **
**
On Wed, Jun 20, 2018 at 06:35:49PM +0200, Maximilian Pichler wrote:
> On Wed, Jun 20, 2018 at 6:27 PM, Tomasz Rola wrote:
> > On my Linux box:
>
> ?
>
> > cat HUGE | /usr/bin/time dd bs=1 count=1234944 | wc -c
>
> stdin might be something much faster than your disk, in which case the
>
On Wed, Jun 20, 2018 at 6:27 PM, Tomasz Rola wrote:
> On my Linux box:
?
> cat HUGE | /usr/bin/time dd bs=1 count=1234944 | wc -c
stdin might be something much faster than your disk, in which case the
relative cost of bs=1 increases.
> cat HUGE | /usr/bin/time dd bs=1024 count=1206 | wc -c
On Wed, Jun 20, 2018 at 06:01:21PM +0200, Maximilian Pichler wrote:
> On Wed, Jun 20, 2018 at 5:50 PM, Solene Rapenne wrote:
> > it's slow because it flushes the output every byte, what would you
> > expect? Maybe you should do in a different manner.
>
> I know, my question is what such a
On Wed, Jun 20, 2018 at 5:50 PM, Solene Rapenne wrote:
> it's slow because it flushes the output every byte, what would you
> expect? Maybe you should do in a different manner.
I know, my question is what such a different manner might look like. :)
Maximilian Pichler writes:
> dd bs=1 count=1234567 will copy 1234567 bytes and then stop, but it's slow.
>
> I can't seem to think of a faster command that also works in the
> presence of short reads and blocking. There is ghead -c from coreutils
> in ports, but this should be possible in base,
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