On Mon, 15 Jan 2007, wrote: > On 1/15/07, Mike Miller <mbmiller at taxa.epi.umn.edu> wrote: >> On Mon, 15 Jan 2007, wrote: >> >> > On 1/12/07, Dan Drake <dan at dandrake.org> wrote: >> > >> >> I'm looking for a regular expression that's guaranteed to never match >> >> anything. >> > >> > Ive used $^ before. But it does depend on how you are using it. the >> > end-of-string followed by a beginning-of-string can show up if $ and ^ >> > match new-lines. >> >> >> I don't understand how that can fail. How can $ and ^ match newlines? >> Is that something that can be affected by command line arguments? When I >> tried it, it seemed to work very well, so I like your idea. It does not >> match anything in a string of consecutive newlines, for example. > > > Im not a big python person, but in perl if you add the m modifier for > "multiple lines" it changes the definition of ^ and $ to match newlines. > I assumed python would have something like it. As long as they keep > their standard definitions, though, you should never find the end of a > string before the beginning. I had forgotten that this was about a python regexp. Still, I mostly use perl and I am interested personally in understanding this better. I can't get it to mess up. For example: # echo 'abcd efgh' | gawk '{print $1"\n\n"$2}' | perl -pe 's/$^/X/ms' abcd efgh What am I doing wrong? I can't figure out how to get "$^" to match anything. Mike