Hello Ryan, * Ryan B wrote on Sun, Jul 18, 2010 at 08:06:46PM CEST: > hi all! i'm trying to use gnu sed's M extension for multiline regex > pattern matching, but i can't get it to work. i'm using gnu sed 4.2.1 > on ubuntu lucid. as a data point, other gnu extensions like I (case > insensitive) work happily.
There is a misunderstanding here. The M modifier does not change the line-oriented operation mode of sed. In order to to multi-line matching, you first need to get more than one line into pattern space, e.g., with the N command. Then, you can match inner newlines with \n (portably to Posix sed even): $ (echo a; echo b) | sed 'N; s,a\nb,X,' X $ Now, the (GNU sed-specific) M modifier allows to match an inner newline even with ^ or $ (which otherwise only match at the beginning or the end of the pattern space: $ (echo a; echo b) | sed 'N; s,a$,X,' a b $ (echo a; echo b) | sed 'N; s,a$,X,M' X b Of course, if your input file consists of more than two lines, and your multi-line matching is supposed to happen at each line, not just at even line numbers, take care to not discard both lines you slurped in: $ (echo a; echo a; echo a; echo a) | sed 'N; s,a$,X,M' X a X a $ (echo a; echo a; echo a; echo a) | sed -n ' :do $p N s,a$,X,M P D bdo' X X X a Hope that helps. Cheers, Ralf
