Why doesnt work regex

问题

Code Example

14> case re:run("5162754", "/^\d+$/") of {match, _} -> ok end.
** exception error: no case clause matching nomatch  
15> case re:run(<<"5162754">>, "/^\d+$/") of {match, _} -> ok end.
** exception error: no case clause matching nomatch

Why doesn't it match?

回答1:

Two things:

1. The regular expression you pass to re:run shouldn't be surrounded by /. In other languages, you write a regexp inside / signs, but in Erlang, regexps are always written as strings, and thus no / signs are necessary.

2. In an Erlang string, \d represents the "delete" character (code 127). What you actually want in your regexp is a backslash followed by the letter d. To achieve that, you need to escape the backslash with another backslash:

   > re:run("5162754", "^\\d+$").
   {match,[{0,7}]}
   

回答2:

Try to use [0-9] it will also works and no problems with backslashes

re:run("5162754", "^[0-9]+$").

来源：https://stackoverflow.com/questions/28475485/why-doesnt-work-regex