Parsing valid parent directories with regex

Question

Given the string a/b/c/d which represents a fully-qualified sub-directory I would like to generate a series of strings for each step up the parent tree, i.e.

Answer 1

One solution building on idea in this other question:

• reverse the string to be matched: d/c/b/a For instance in PHP use strrev($string )
• match with (?=(/(?:\w+(?:/|$))+))

This give you

/c/b/a
/b/a
/a

Then reverse the matches with strrev($string )

This give you

a/b/c/
a/b/
a/

If you had .NET not PCRE you could do matching right to left and proably come up with same.

Answer 2

Completely different answer without reversing string.

(?<=((?:\w+(?:/|$))+(?=\w)))

This matches

a/
a/b/
a/b/c/

but you have to use C# which use variable lookbehind

Answer 3

Yes, it's possible:

/([^\/]*)\//

So basically it replaces your .*? with [^/]*, and it does not have to be non-greedy. Since / is a special character in your case, you will have to escape it, like so: [^\/]*.