Need help with back-reference matching on regex

Question

Hey there,

I have been working on this regex:
{link=([^|{}]+)\||([^|{}]+)\||([^|{}]+)}

I wish to capture any non-pipe or bracket chars and place them in appropriate backreference (group).

How can I return the following:

1. If test string is {link=a} return a into group 3.
2. If test string is {link=a|b} return a into group 2, b into group 3.
3. If test string is {link=a|b|c} return a into group 1, b into group 2, c into group 3.

Having issues where the strings are not correctly being picked up into correct groups on all permutations with the above regex. I think I have bracket grouping issues and/or OR (|) statement issues.

Thanks in advance.

Answer 1

in python, but the syntax should be the same,

#!/usr/bin/python

import re
ptn = re.compile(r"""
    {link=
    (?:
      (?:([^|}]+)\|)?
      (?:([^|}]+)\|)
    )?
    ([^|}]+)
    }
    """, re.VERBOSE)

l = [
    "{link=a}",
    "{link=a|b}",
    "{link=a|b|c}",
    "{link=a} {link=a|b} {link=a|b|c}",
]
for s in l:
    for m in ptn.finditer(s):
        print "%s => matchs: %s => m.group(3): %s" % (
                s, m.group(0), m.group(3))

and result:

{link=a} => matchs: {link=a} => m.group(3): a
{link=a|b} => matchs: {link=a|b} => m.group(3): b
{link=a|b|c} => matchs: {link=a|b|c} => m.group(3): c
{link=a} {link=a|b} {link=a|b|c} => matchs: {link=a} => m.group(3): a
{link=a} {link=a|b} {link=a|b|c} => matchs: {link=a|b} => m.group(3): b
{link=a} {link=a|b} {link=a|b|c} => matchs: {link=a|b|c} => m.group(3): c

Answer 2

How about capturing all the matches in the same group?

string[] tests = {
    "{link=a}",
    "{link=a|b}",
    "{link=a|b|c}",
};

var link = @"(?<link>[^|]+)";
var pattern = new Regex(String.Format(@"^\{{link={0}(\|{0})*\}}$", link));

foreach (var s in tests) {
    Match m = pattern.Match(s);

    if (!m.Success) {
        Console.WriteLine("{0}: FAIL", s);
        continue;
    }

    Console.Write("{0}: PASS ", s);
    foreach (var l in m.Groups["link"].Captures)
        Console.Write("[{0}]", l);
    Console.WriteLine();
}

Output:

{link=a}: PASS [a]
{link=a|b}: PASS [a][b]
{link=a|b|c}: PASS [a][b][c]