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Groups > comp.os.linux.misc > #29703
| From | Eli the Bearded <*@eli.users.panix.com> |
|---|---|
| Newsgroups | comp.os.linux.misc |
| Subject | Re: Reading a file from the back |
| Date | 2020-04-10 20:37 +0000 |
| Organization | Some absurd concept |
| Message-ID | <eli$2004101637@qaz.wtf> (permalink) |
| References | <r6hq2v$5bd$2@dont-email.me> <r6i5kr$q9o$2@dont-email.me> <slrnr91hqg.8ub.jj@iridium.wf32df> |
In comp.os.linux.misc, Jim Jackson <jj@franjam.org.uk> wrote:
> On 2020-04-07, Rich <rich@example.invalid> wrote:
>>> What is that command?
>> If by "from the end upwards" you really mean "backwards" (as in reverse
>> byte order) then 'tac' is the command you are looking for.
> eerrrmmm... tac does reverse line (not byte) order!
I'm not aware of a standard tool that does 100% reverse byte order.
I've seen it as a programming challenge.
tac prints files line-by-line backwards.
rev reverses bytes line-by-line
`tac | rev` gets you a naive reversal, but the catch is, newlines are
not included.
In:
ABCDEFG\n
HIJKLMN\n
out of tac:
HIJKLMN\n
ABCDEFG\n
out of rev:
GFEDCBA\n
NMLKJIH\n
out of tac|rev:
NMLKJIH\n
GFEDCBA\n
out of a byte-by-byre reversal:
\nNMLKJIH
\nGFEDCBA
A simple byte-by-byte reverser:
perl -ne '$all .= $_; END{ print scalar reverse $all }'
A more sophisticated tool would not rely on storing it all in
memory for every usage.
Elijah
------
optimized the perl for readibility, not speed or code golf
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Reading a file from the back Dieter Britz <dieterhansbritz@gmail.com> - 2020-04-07 12:01 +0000
Re: Reading a file from the back Vasco Costa <vasco.costa@invalid.invalid> - 2020-04-07 12:12 +0000
Re: Reading a file from the back Fenris <fenris@invalid.invalid> - 2020-04-07 12:12 +0000
Re: Reading a file from the back Rich <rich@example.invalid> - 2020-04-07 15:18 +0000
Re: Reading a file from the back Jim Jackson <jj@franjam.org.uk> - 2020-04-10 19:21 +0000
Re: Reading a file from the back Eli the Bearded <*@eli.users.panix.com> - 2020-04-10 20:37 +0000
Re: Reading a file from the back Eric Pozharski <whynot@pozharski.name> - 2020-04-11 15:22 +0300
Re: Reading a file from the back Eli the Bearded <*@eli.users.panix.com> - 2020-04-13 01:03 +0000
Re: Reading a file from the back Eric Pozharski <whynot@pozharski.name> - 2020-04-13 11:16 +0300
Re: Reading a file from the back Eli the Bearded <*@eli.users.panix.com> - 2020-04-13 20:01 +0000
Re: Reading a file from the back Eric Pozharski <whynot@pozharski.name> - 2020-04-14 12:14 +0300
Re: Reading a file from the back Eli the Bearded <*@eli.users.panix.com> - 2020-04-14 16:50 +0000
Re: Reading a file from the back Rich <rich@example.invalid> - 2020-04-10 21:40 +0000
Re: Reading a file from the back The Natural Philosopher <tnp@invalid.invalid> - 2020-04-08 08:55 +0100
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