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From: "John Levine" <johnl@iecc.com>
To: freebsd-questions@freebsd.org
Cc: zarniwhoop@ntlworld.com
Subject: Re: grep problem
In-Reply-To: <20171207010801.GA10604@milliways.localdomain>
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In article <20171207010801.GA10604@milliways.localdomain> you write:
>> $ echo 'a-b' | grep  '-b'
>> Usage: grep [OPTION]... PATTERN [FILE]...
>> Try `grep --help' for more information.
>> 
>> $ echo 'a-b' | grep  '\-b'
>> a-b

>In gnu grep, '-' indicates it should read from STDIN, I assume that
>FreeBSD's grep is the same.

Close, but not quite.  A quick peek at the grep man page (you did look
at the man page, didn't you?) reveals that -b is a flag telling what
byte offset to start at.  A more normal way to prevent your pattern
from being treated as a flag is to tell it that it's a pattern:

$ echo a-b | grep -e -b

R's,
John