From: Andrey Repin <anrdaemon@yandex.ru>
To: Eliot Moss <moss@cs.umass.edu>, cygwin@cygwin.com
Subject: Re: bug with grep 3.0.2 in cygwin 3.0.7
Date: Fri, 30 Aug 2019 07:55:00 -0000 [thread overview]
Message-ID: <42748516.20190830104400@yandex.ru> (raw)
In-Reply-To: <806ab587-a07c-1616-1486-ebb258ace1d9@cs.umass.edu>
Greetings, Eliot Moss!
>>> I encounter some problem with grep option -E on cygwin 3.0.7
>>
>>
>>> echo "a^b" | grep "a^b" #answer a^b ie it's OK
>>> but
>>> echo "a^b" | grep -E "a^b" #answer nothing " for me it's KO
>>
>> That's an expected result of an impossible constraint.
>>
>>> I have to backslash ^ to be OK like : grep -E 'a\^b'
>>
>> Yes.
>>
>>> Is-it a bug ?
>>
>> No.
>>
>>> I don't know if all versions of cygwin and grep are concerned.
>>
>> RTFM, this is regexp basics.
> There was a really great answer to this earlier. I tried an
> answer, but was wrong. One has to read the "fine print" really
> carefully. At first I thought it was a bug, at least in the
> documentation, but the meaning of a^b, when ^ is the metacharacter,
> is kind of subtle (IMO at least). It's easy to miss that
> subtlety and think that if ^ is not at the beginning of an
> expression it will be treated as an ordinary character ...
> But my main point is that RTM would be enough; RTFM seemed
> to me perhaps a little more rude than necessary.
Adding to the earlier answers (sorry, replying on the road is not efficient),
there's a https://www.regular-expressions.info/
Which contains a great deal of information about RE, their kinds, caveats and
implementations in various languages.
--
With best regards,
Andrey Repin
Friday, August 30, 2019 10:42:35
Sorry for my terrible english...
--
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next prev parent reply other threads:[~2019-08-30 7:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1910922536.1217465852.1566975322390.JavaMail.root@zimbra76-e14.priv.proxad.net>
2019-08-28 8:32 ` akiki
2019-08-28 12:51 ` Eliot Moss
2019-08-28 13:33 ` Eric Blake
2019-08-29 19:20 ` Andrey Repin
2019-08-30 6:12 ` Eliot Moss
2019-08-30 7:48 ` Brian Inglis
2019-08-30 15:34 ` Eliot Moss
2019-08-30 7:50 ` Duncan Roe
2019-08-30 13:04 ` Jose Isaias Cabrera
2019-08-30 7:55 ` Andrey Repin [this message]
2019-09-23 14:42 ` Chris Wagner
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