Grep is my enemy...

[Stephen Allen]

Yes, this old chestnut again... sorry!

I have a pattern file with keywords/phrases, 1 per line, and now and 
there there are blank lines scattered through the file.

I want to filter the patterns on the fly (getting rid of the blank 
lines), and using the result as the pattern file for grep -f.

I also want to supply a string for the grep data, not a file.  So my 
command looks something like this:

    grep -i -v '^[     ]*$' <pattern_file> | grep -f <stdin> <string>

Obviously, grep doesn't like the <string> part and complains bitterly 
that it can't find the file.

Can this be done in one statement?  I'd like to keep it on one statement 
because it will be part of a procmail recipe, and I don't want to keep 
writing temporary files to disk.

Many thanks (and sorry for being a PITA over grep)
Steve :)