Multiline Regular Expression with Erlang re module

Question

Hi,

Failed to get Erlang re work for multiline, please help!

> re:run("hello,\nworld", "o,.*w", [multiline]).
nomatch
> re:run("hello,\nworld", "o,.*w", [multiline, {newline, lf}]).
nomatch

> {ok, MP} = re:compile("o,.*w", [multiline]).
{ok,{re_pattern,0,0,
                <<69,82,67,80,55,0,0,0,2,0,0,0,7,0,0,0,0,0,0,0,111,0,
                  119,...>>}}
> re:run("hello,\nworld", MP).
nomatch

> re:run("hello,\nworld", ",\nw").
{match,[{5,3}]}

Answer 1

use the dotall option, i.e.

> re:run("hello,\nworld", "o,.*w", [dotall]).
{match,[{4,4}]}

Answer 2

The multiline option only tells the regex engine to treat ^ not only as the start of the string, but also as the start of a new line and it also tells the engine to treat $ not only as the end of the string, but as the end of a line.

Try this instead:

re:run("hello,\nworld", "o,.*w", [dotall])

The dotall option will tell the regex engine to also let line breaks be matched by the DOT meta character.