C# - Regex for file paths e.g. C:\test\test.exe

I decided to post this answer which does use a regular expression.

^(?:[a-zA-Z]\:|\\\\[\w\.]+\\[\w.$]+)\\(?:[\w]+\\)*\w([\w.])+$

Works for these:

\\test\test$\TEST.xls
\\server\share\folder\myfile.txt
\\server\share\myfile.txt
\\123.123.123.123\share\folder\myfile.txt
c:\folder\myfile.txt
c:\folder\myfileWithoutExtension

Edit: Added example usage:

if (Regex.IsMatch (text, @"^(?:[a-zA-Z]\:|\\\\[\w\.]+\\[\w.$]+)\\(?:[\w]+\\)*\w([\w.])+$"))
{
  // Valid
}

*Edit: * This is an approximation of the paths you could see. If possible, it is probably better to use the Path class or FileInfo class to see if a file or folder exists.

I would recommend using the Path class instead of a Regex if your goal is to work with filenames.

For example, you can call Path.GetFullPath to "verify" a path, as it will raise an ArgumentException if the path contains invalid characters, as well as other exceptiosn if the path is too long, etc. This will handle all of the rules, which will be difficult to get correct with a Regex.

This is regular expression for Windows paths:

(^([a-z]|[A-Z]):(?=\\(?![\0-\37<>:"/\\|?*])|\/(?![\0-\37<>:"/\\|?*])|$)|^\\(?=[\\\/][^\0-\37<>:"/\\|?*]+)|^(?=(\\|\/)$)|^\.(?=(\\|\/)$)|^\.\.(?=(\\|\/)$)|^(?=(\\|\/)[^\0-\37<>:"/\\|?*]+)|^\.(?=(\\|\/)[^\0-\37<>:"/\\|?*]+)|^\.\.(?=(\\|\/)[^\0-\37<>:"/\\|?*]+))((\\|\/)[^\0-\37<>:"/\\|?*]+|(\\|\/)$)*()$

And this is for UNIX/Linux paths

^\/$|(^(?=\/)|^\.|^\.\.)(\/(?=[^/\0])[^/\0]+)*\/?$

Here are my tests:

Win Regex

Unix Regex

These works with Javascript

EDIT I've added relative paths, (../, ./, ../something)

EDIT 2 I've added paths starting with tilde for unix, (~/, ~, ~/something)