From: Bakul Shah <bakul@iitbombay.org>
To: TUHS main list <tuhs@minnie.tuhs.org>
Subject: Re: [TUHS] head/sed/tail (was The Unix shell: a 50-year view)
Date: Thu, 15 Jul 2021 15:29:40 -0700 [thread overview]
Message-ID: <F78F5E0A-0DBF-4739-B13F-48367BBEF358@iitbombay.org> (raw)
In-Reply-To: <CAKH6PiWDnDBEE9vWRU+6kAuEcMNFdpJ9tiv0=9VUr-LMJRRBbw@mail.gmail.com>
On Jul 14, 2021, at 7:38 PM, Douglas McIlroy <douglas.mcilroy@dartmouth.edu> wrote:
>
> -r is weird because it enables backwards reading, but only as
> limited by count. Better would be a program, say revfile, that simply
> reads backwards by lines. Then tail p has an elegant implementation:
> revfile p | head | revfile
tail -n can be smarter in that it can simply read the last K bytes
and see if there are n lines. If not, it can read back further.
revfile would have to read the whole file, which could be a lot
more than n lines! tail -n < /dev/tty may never terminate but it
will use a small finite amount of memory.
-- Bakul
next prev parent reply other threads:[~2021-07-15 22:29 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 2:38 Douglas McIlroy
2021-07-15 4:19 ` arnold
2021-07-15 4:25 ` Adam Thornton
2021-07-15 7:20 ` Thomas Paulsen
2021-07-15 14:28 ` Theodore Y. Ts'o
2021-07-15 22:29 ` Bakul Shah [this message]
2021-07-15 15:44 Norman Wilson
2021-07-15 16:54 Nelson H. F. Beebe
2021-07-15 19:01 Norman Wilson
2021-07-15 19:27 ` Clem Cole
2021-07-15 19:28 ` Clem Cole
2021-07-15 19:34 ` Warner Losh
2021-07-16 7:38 ` arnold
2021-07-16 16:09 ` Warner Losh
2021-07-16 8:05 ` Lars Brinkhoff
2021-07-16 14:19 ` Clem Cole
2021-07-17 0:34 ` Charles Anthony
2021-07-15 21:26 Paul Ruizendaal
2021-07-15 22:00 Douglas McIlroy
2021-07-15 22:12 ` John Cowan
2021-07-15 22:26 Nelson H. F. Beebe
2021-07-15 23:18 ` Jim Davis
2021-07-16 0:02 ` John Floren
2021-07-16 1:02 ` Nelson H. F. Beebe
2021-07-16 8:27 ` Lars Brinkhoff
2021-07-16 15:28 ` John Floren
2021-07-16 0:02 ` Clem Cole
2021-07-16 0:25 ` Nelson H. F. Beebe
2021-07-16 8:50 ` Lars Brinkhoff
2021-07-16 12:09 Douglas McIlroy
2021-07-16 14:32 ` Bakul Shah
[not found] <CAKH6PiW58PDPb5HRi12aKE+mT+O8AjETr9R51Db6U3KcEp_KkA@mail.gmail.com>
2021-07-16 14:17 ` Nelson H. F. Beebe
2021-07-16 16:13 ` Theodore Y. Ts'o
2021-07-18 20:07 Douglas McIlroy
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