How to edit "Full Windows Folder Path Regular Expression" - regex

Question

Hay this regualr expression working fine for Full Windows Folder Path
^([A-Za-z]:|\\{2}([-\w]+|((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))\\(([^"*/:?|<>\\,;[\]+=.\x00-\x20]|\.[.\x20]*[^"*/:?|<>\\,;[\]+=.\x00-\x20])([^"*/:?|<>\\,;[\]+=\x00-\x1F]*[^"*/:?|<>\\,;[\]+=\x00-\x20])?))\\([^"*/:?|<>\\.\x00-\x20]([^"*/:?|<>\\\x00-\x1F]*[^"*/:?|<>\\.\x00-\x20])?\\)*$
Matches
d:\, \\Dpk\T c\, E:\reference\h101\, \\be\projects$\Wield\Rff\, \\70.60.44.88\T d\SPC2\
Non-Matches
j:ohn\, \\Dpk\, G:\GD, \\cae\.. ..\, \\70.60.44\T d\SPC2\
PROBLEM:
THIS EXPRESSION REQUIRED "\" END OF PATH.
HOW CAN I EDIT THIS EXPRESSION SO USER CAN ENTER PATH LIKE
C:\Folder1, C:\Folder 1\Sub Folder

Answer 1

There are two ways to approach this problem:
Understand the regex (way harder than necessary) and fix it to your specification (may be buggy)
Who cares how the regex does its thing (it seems to do what you need) and modify your input to conform to what you think the regex does
The second approach means that you just check if the input string ends with \. If it doesn't then just add it on, then let the regex does it magic.
I normally wouldn't recommend this ignorant alternative, but this may be an exception.
Blackboxing
Here's how I'm "solving" this problem:
There's a magic box, who knows how it works but it does 99% of the time
We want it to work 100% of the time
It's simpler to fix the 1% so it works with the magic box rather than fixing the magic box itself (because this would require understanding of how the magic box works)
Then just fix the 1% manually and leave the magic box alone
Deciphering the black magic
That said, we can certainly try to take a look at the regex. Here's the same pattern but reformatted in free-spacing/comments mode, i.e. (?x) in e.g. Java.
^
( [A-Za-z]:
| \\{2} ( [-\w]+
| (
(25[0-5]
|2[0-4][0-9]
|[01]?[0-9][0-9]?
)\.
){3}
(25[0-5]
|2[0-4][0-9]
|[01]?[0-9][0-9]?
)
)
\\ (
( [^"*/:?|<>\\,;[\]+=.\x00-\x20]
| \.[.\x20]* [^"*/:?|<>\\,;[\]+=.\x00-\x20]
)
( [^"*/:?|<>\\,;[\]+=\x00-\x1F]*
[^"*/:?|<>\\,;[\]+=\x00-\x20]
)?
)
)
\\ (
[^"*/:?|<>\\.\x00-\x20]
(
[^"*/:?|<>\\\x00-\x1F]*
[^"*/:?|<>\\.\x00-\x20]
)?
\\
)*
$
The main skeleton of the pattern is as follows:
^
(head)
\\ (
bodypart
\\
)*
$
Based from this higher-level view, it looks like an optional trailing \ can be supported by adding ? on the two \\ following the (head) part:
^
(head)
\\?(
bodypart
\\?
)*
$
References
regular-expressions.info/Question Mark for Optional
Note on catastrophic backtracking
You should generally be very wary of nesting repetition modifiers (a ? inside a * in this case), but for this specific pattern it's "okay", because the bodypart doesn't match \.
References
regular-expressions.info/Catastrophic Backtracking

Answer 2

I don't understand your regular expression at all. But I bet all you need to do is find the bit or bits that match the trailing "\", and add a single question mark after that bit or those bits.

Answer 3

The regex you provided seems to mismatch "C:\?tmp" which is an invalid windows path.
I have figured out one solution but works in windows only. You may have a try with this one:
"^[A-Za-z]:(?:\\\\(?![\"*/:?|<>\\\\,;[\\]+=.\\x00-\\x20])[^\"*/:?|<>\\\\[\\]]+){0,}(?:\\\\)?$"
This regex ignores the last "\" which hinders you.
I've tested with pcre.lib(5.5) in VS2005.
Hope it helps!

Answer 4

I know this question is roughly 4 years old, but the following may be sufficient:
string validWindowsOrUncPath = #"^(?:(?:[a-z]:)|(?:\\\\[^\\*\?\:;\0]*))(?:\\[^\\*\?\:;\0]*)+$";
(to be used with IgnoreCase option).
Edit:
I even came to this one, which can extract the root and each part in named groups:
string validWindowsOrUncPath = #"^(?<Root>(?:[a-z]:)|(?:\\\\[^\\*\?\:;\0]*))(?:\\(?<Part>[^\\*\?\:;\0]*))+$";