From: Ralph Corderoy <ralph@inputplus.co.uk>
To: Computer Old Farts Followers <coff@tuhs.org>
Subject: [COFF] Re: Grep has gone overboard
Date: Mon, 30 May 2022 09:16:04 +0100 [thread overview]
Message-ID: <20220530081604.A9FBF21F8A@orac.inputplus.co.uk> (raw)
In-Reply-To: <F83DB452-12EA-4EA4-8193-76B8FB5644D2@iitbombay.org>
Hi Bakul,
> You can write a program to generate all permutations and use that as
> your regexp. For example abc maps to abc|acb|bac|bca|cab|cba.
Being lazy, I tend to use a shell's brace expansion and then whittle it
down to generate permutations. I keep thinking it's surprising there's
no Bell Labs program to produce them given there's things like
factor(1).
The brace expansion is wasteful as it's going from n**l down to n! and
it can result in the old bash here not responding to SIGINT for a while
if it's producing gazillions.
$ printf '%s\n' {b,a,d,u,g,l,y}{b,a,d,u,g,l,y}{b,a,d,u,g,l,y}\
> {b,a,d,u,g,l,y}{b,a,d,u,g,l,y}{b,a,d,u,g,l,y}{b,a,d,u,g,l,y} |
> egrep -v '(.).*\1' |
> fgrep -x -f - /usr/share/dict/words
ladybug
$
--
Cheers, Ralph.
next prev parent reply other threads:[~2022-05-30 8:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-30 4:12 [COFF] " Dave Horsfall
2022-05-30 4:47 ` [COFF] " Bakul Shah
2022-05-30 6:35 ` Michael Kjörling
2022-05-30 6:51 ` Bakul Shah
2022-05-30 8:26 ` Ralph Corderoy
2022-05-30 8:01 ` Ralph Corderoy
2022-05-30 8:16 ` Ralph Corderoy [this message]
2022-05-30 8:43 ` Bakul Shah
2022-05-30 9:19 ` Ralph Corderoy
2022-05-30 7:38 ` Ralph Corderoy
2022-05-30 7:44 ` Ralph Corderoy
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220530081604.A9FBF21F8A@orac.inputplus.co.uk \
--to=ralph@inputplus.co.uk \
--cc=coff@tuhs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).