[wplug] simple regex

[Bob Schmertz]

Duncan Hutty wrote:
>>
>>I'm trying to parse a file for lines that do not contain the '@'
>> character. Some lines of the input contain this character, some do
>> not.
>>
>>grep '[^@]' prints all lines, regardless of whether they include '@' 
>>or not.
>

Whereupon Mike Kuentz (2) incurred the wrath of Bob on Jun 25, by saying

>$ grep -v '@' filename 
>
>Should do it.  -v gives you the inverse of what you are looking for.  In
>your expression the ^ is interpreted as the beginning of the line.  It's not
><NOT> as I think you were trying.

To which Bob Schmertz now responds:

In this context, it *is* <NOT>.  But the reason it doesn't work as you
expected is because it means "show me lines which contain at least one 
character which is not '@'.  Thus the line

@@@@@@@@@@@@@t@@@@@@@@@@@

would match because the 't' matches the 'not a @' requirement.

Another thing you could do would be

grep '^[^@]*$'

which would mean "the whole line should consist of characters which are 
not @".  But grep -v is easier, especially when you want to exclude more 
complex things.

-- 
Cheers,
Bob Schmertz