Re: Issue with reading regexes from a file

[Benno Schulenberg]

David Corlette wrote:
> Not sure if this is a bug, a doc issue, or a misunderstanding as
> to what it's supposed to do, but I'm getting strange results when
> I attempt to use the "-f" option in combination with the '-P'
> option.

In the man page of grep-2.5.3 it says:

    -P, --perl-regexp
              Interpret PATTERN as a Perl regular expression.
              This is  highly  experimental and grep -P may warn
              of unimplemented features.

It should probably also say that it sometimes simply doesn't work.

Your grep is probably older and doesn't yet warn of the experimental 
nature of -P.

Benno