This brings me to a very nice regular expression. It is the one being recommended in

    RFC3986 "Uniform Resource Identifier (URI): Generic Syntax"
    by  T. Berners-Lee, R. Fielding and L. Masinter

    https://tools.ietf.org/html/rfc3986

to parse an URI. Having seen so many regular expressions, that try to match it all, this regex tries to match as little as possible, while, at the same time, matches any string, because it matches no string. It does not define what to match, but what not to match and making every match optional.

According part from the spec:

    ^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
     12            3  4          5       6  7        8 9

    The numbers in the second line above are only to assist readability;
    they indicate the reference points for each subexpression (i.e., each
    paired parenthesis).  We refer to the value matched for subexpression
    <n> as $<n>.  For example, matching the above expression to

      http://www.ics.uci.edu/pub/ietf/uri/#Related

    results in the following subexpression matches:

      $1 = http:
      $2 = http
      $3 = //www.ics.uci.edu
      $4 = www.ics.uci.edu
      $5 = /pub/ietf/uri/
      $6 = <undefined>
      $7 = <undefined>
      $8 = #Related
      $9 = Related

    where <undefined> indicates that the component is not present, as is
    the case for the query component in the above example.  Therefore, we
    can determine the value of the five components as

      scheme    = $2
      authority = $4
      path      = $5
      query     = $7
      fragment  = $9