Re: extract line

[Loops]

Probably there is a shorter one liner than this:

perl -F: -ane 'BEGIN {open K, "<file2"; $h{0+$_}=1 for <K>} print if e
+xists $h{$F[0]}' file1

[rjt]

How about this?

perl -pe'open _,file2;0+$_~~[<_>]or$_=""' file1

47 chars, versus 91 (84, removing unnecessary whitespace). This one's definitely "just for fun", though, due to now-experimental smartmatch and re-reading of file2.