Regex to get last directory and filename from a path

Question

So, I have an example path c:\\folder1\\folder2\\folder3\\file.txt I want regex to pull folder3\\file.txt

I figured this would be everything after

1. a slash
2. followed by any number of non slash characters
3. followed by a slash
4. followed by any number of non slash characters
5. followed by a dot 
5.1 that is not (eventually) followed by a slash

I've got most of it working

\\(?=[^\\]*(?=\\(?=[^\\]*(?=[\.]))))(.*)

unless I do this:

c:\\folder1\\folder2\\fol.der3\\file.txt (fol.der3 is the name of the directory)

or this

c:\\folder1\\folder2\\folder3\\file.txt\\ (technically there is no file here)

So, I've got everything except step 5.1

So, I tried adding a negative lookahead after my dot seeking lookahead so it would exclude dots that have a slash somewhere after them:

(?=[\.][^\\]*(?![\\]))

but that didnt work

Any ideas?

Thanks Chris

Answer 1

You could use a capturing group instead of using the lookaround and while still making use of the negative character classes .

\\([^\\]+\\[^\\.]+\.[^\\.]+)$

Explanation

• \\\\ Match \\
• ( Capture group 1
  • [^\\\\]+\\\\ Match 1+ occurrences of any char except \\ and then match \\
  • [^\\\\.]+\\. Match 1+ occurrences of any char except \\ or . and then match \\
  • [^\\\\.]+ Match 1+ occurrences of any char except \\ or .
• ) Close group 1
• $ End of string

Regex demo

Answer 2

[^\\]+\\[^\\]+$

1. [^\\\\]+ - matches any character except \\ one or more times
2. \\\\ - matches a single \\
3. [^\\\\]+ - matches any character except \\ one or more times
4. $ - matches the end of string

This is enough to get the last two pieces of your URI.

Whether the last piece is a folder or a file really can't be determined with regex as

• files are not required to have an extension
• URI of a folder does not end with a slash

Unless you can be sure of your input and that proves one of these two points invalid then the regex should be modified accordingly.