Rules for Pattern Matching for TTL Selection Property

Listed below are the rules for pattern matching used for the reg_expression component of the TTL Selection Based on URL property, described in "URL Policy". These rules are taken from Section 3C of the Solaris regexec man page.

1. If subexpression i in a regular expression is not contained within another subexpression, and it participated in the match several times, then the byte offsets in pmatch[i] will delimit the last such match.

2. If subexpression i is not contained within another subexpression, and it did not participate in an otherwise successful match, the byte offsets in pmatch[i] will be -1. A subexpression does not participate in the match when:

   • * or \{ \} appears immediately after the subexpression in a basic regular expression, or *, ?, or {} appears immediately after the subexpression in an extended regular expression, and the subexpression did not match (matched zero times)

     or

   • | is used in an extended regular expression to select this subexpression or another, and the other subexpression matched.

3. If subexpression i is contained within another subexpression j, and i is not contained within any other subexpression that is contained within j, and a match of subexpression j is reported in pmatch[j], then the match or non-match of subexpression i reported in pmatch[i] will be as described in 1. and 2. above, but within the substring reported in pmatch[j] rather than the whole string.

4. If subexpression i is contained in subexpression j, and the byte offsets in pmatch[j] are -1, then the pointers in pmatch[i] also will be -1.

5. If subexpression i matched a zero-length string, then both byte offsets in pmatch[i] will be the byte offset of the character or NULL terminator immediately following the zero-length string.