8

I would like a regular expression to match a valid absolute Windows directory path, where directory names can contain spaces.

Example matches:

C:\pictures\holiday  (without trailing backslash)
C:\pictures\holiday\ (or with trailing backslash)
C:\ pictures\holiday
C:\ pictures\holiday\
C:\pictures \ holiday
C:\pictures \ holiday\
C:\pictures\ holiday \

Example fails:

\pictures\holiday (no relative path allowed)
C:\pictures*\holiday (not a valid directory path)

I have tried ^[a-zA-Z]:(\\\w+)*([\\])?$ but that does not match the spaces.

I have also tried ^[a-zA-Z]:(\s)*(\\\w+)*(\s)*([\\])?$ but that works erratically.

Regular expressions are my last resort. I have also tried to validate the text box using a non-regex solution, like in this answer. But I have not found a method that works for spaces.

Thanks in advance!

Improve this question
11
  • 3
    why it C:\pictures@!#$1afaf\holiday isn't a valid directory? I could be able to create a directory like that. Commented Jul 11, 2014 at 16:57
  • 3
    Why isn't "C:\pictures\holiday\photo.jpg" a valid directory path? I can name a directory "photo.jpg". There's no difference in the accepted pattern for directories versus filenames because they're both "files", just with different attributes. Commented Jul 11, 2014 at 16:59
  • 1
    No threats if the user is specifying a location on his own machine. If the path data is not coming to your machine, why would you worry? If the user is specifying a file/folder location to be uploaded, the file reading part of your program will complain anyway. And the file-reader will handle more cases (like dots, network paths etc.) Commented Jul 11, 2014 at 17:05
  • 1
    I know the feeling. We are this close to building a fusion reactor. For 50 years now. Commented Jul 11, 2014 at 17:13
  • 1
    I found a better solution to this problem that does not require regular expressions. The solution is to use an improved folder browser, namely the Windows 7 browser. Install the Windows 7 API Code Pack. In Visual Studio 2013 this can be done by going to Tools -> Library Package Manager -> Package Manager Console and running the command Install-Package Windows7APICodePack-Shell. Then you will have access to Microsoft.WindowsAPICodePack.Dialogs.CommonOpenFileDialog which includes all the validation! SHAZAM!! Commented Jul 14, 2014 at 9:12

3 Answers 3

Reset to default
15

Here's a regex that will work:

^[a-zA-Z]:\\(((?![<>:"/\\|?*]).)+((?<![ .])\\)?)*$

It makes the path conform to the NTFS standard (see the MSDN spec). I'll break it down:

^[a-zA-Z]:\\ matches single drive letter, with colon and backslash

(?![<>:"/\\|?*]) is a negative lookahead to ensure the next character is not invalid

((?![<>:"/\\|?*]).)+ wraps that lookahead, followed by the next character, any number of times

(?<![ .])\\ is a negative lookbehind to ensure the file/directory doesn't end with a space or period. Please note: Lookbehinds are not fully implemented everywhere just yet.

All of that is is repeated 0 to many times, with the last backslash optional.

For many use cases it may be best to restrict the path length to 256 characters. To do so, replace *with {0,256}.

EDIT: allow root directory

Improve this answer
Sign up to request clarification or add additional context in comments.

8 Comments

When I put that in a string literal, Visual Studio doesn't like it and marks it in red. Just to be sure the characters weren't altered during copy-paste, I typed that thing out by hand and it still flagged it as an error. Match match = Regex.Match(tbOutputFilePath.Text, @"^[a-zA-Z]:\\(((?![<>:"/\\|?*]).)*[^ ]\\)*((?![<>:"/\\|?*]).)*[^ ]\\?$");
you need to escape the double-quotes in the regex
Isn't a C# string literal supposed to do that automatically?
Ah, I think I'm supposed to escape the double quote with another double quote, even in a string literal, as suggested in this answer stackoverflow.com/questions/1928909/…
Alright, I escaped the double-quotes, and this is the resulting regex: @"^[a-zA-Z]:\\(((?![<>:""/\\|?*]).)*[^ ]\\)*((?![<>:""/\\|?*]).)*[^ ]\\?$" It doesn't match a directory containing spaces and having more than one level, and it doesn't match the root directory. For example, it doesn't match C:\ or C:\ pictures \ vacation \ (And I think it broke the comment box because I can't wrap those paths in gray background anymore!) xD
|
1

Following regex expression work for me for validate custom rules against a path-like string.

/^[a-z]:(((\|/)[a-z0-9\s_@-^!#$%&+={}[]]+)+(\|/)?)$/i

var path="C:\\backup\\newFolder" ; // valid
// var path="C:\\backup\\newFolder\\" ; // valid
// var path="C:\/backup\/newFolder\\" ; // valid
// var path="C:\\\backup\newFolder" ; // invalid
// var path="C:\backup//\newFolder" ; // invalid
// var path="C:\backup\new..Folder" ; // invalid


if((/^[a-z]:(((\\|\/)[a-z0-9\s_@\-^!#$%&+={}\[\]]+)+(\\|\/)?)$/i.test(path))) {
    alert("valid path string");
} else {
    alert("Invalid Path String");
}

Improve this answer

Comments

0 
function isFileOrFolderPathValid(path)
{
    var result =  new RegExp(/^[a-z]:((\\|\/)[a-z0-9\s_@\-^!#$%&+={}\[\]]+)+\.[a-zA-Z0-9]+$/i).test(path);

    if (result === true) return true;

    result = new RegExp(/^[a-z]:((\\|\/)[a-z0-9\s_@\-^!#$%&+={}\[\]]+)+$/i).test(path);    

    //result = /^[a-zA-Z]:\\(\w+\\)*\w*$/.test(path);

    return result;
}
Improve this answer

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.