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

Question

I am currently looking for a regex that can help validate a file path e.g.:

C:\test\test2\test.exe

Answer 1

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.

Answer 2

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.

Answer 3

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)

Answer 4

The proposed one is not really good, this one I build for XSD, it's Windows specific:

^(?:[a-zA-Z]\:(\\|\/)|file\:\/\/|\\\\|\.(\/|\\))([^\\\/\:\*\?\<\>\"\|]+(\\|\/){0,1})+$

Answer 5

Try this one for Windows and Linux support: ((?:[a-zA-Z]\:){0,1}(?:[\\/][\w.]+){1,})

Answer 6

I use this regex for capturing valid file/folder paths in windows (including UNCs and %variables%), with the exclusion of root paths like "C:\" or "\\serverName"

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

this regex does not match leading spaces in path elements, so

• "C:\program files" is matched
• "C:\ pathWithLeadingSpace" is not matched

variables are allowed at any level

• "%program files%" is matched
• "C:\my path with inner spaces\%my var with inner spaces%" is matched

Answer 7

regex CmdPrompt("^([A-Z]:[^\<\>\:\"\|\?\*]+)");

Basically we look for everything that's not in the list of forbidden Windows Path Characters:

< (less than)
> (greater than)
: (colon)
" (double quote)
| (vertical bar or pipe)
? (question mark)
* (asterisk)

Answer 8

I know this is really old... but expanding on @agent-j's response I've added named groups, and support for period characters.

^(?<ParentPath>(?:[a-zA-Z]\:|\\\\[\w\s\.]+\\[\w\s\.$]+)\\(?:[\w\s\.]+\\)*)(?<BaseName>[\w\s\.]*?)$

I've saved this at Regexr

Answer 9

I found most of the answers here to be a little hit or miss.

Found a good solution here though:

https://social.msdn.microsoft.com/forums/vstudio/en-US/31d2bc84-c948-4914-8a9d-97b9e788b341/validate-a-network-folder-path

Note* - this is only for network shares - not local files

Answer:

string pattern = @"^\\{2}[\w-]+(\\{1}(([\w-][\w-\s]*[\w-]+[$$]?)|([\w-][$$]?$)))+";
string[] names = { @"\\my-network\somelocation", @"\\my-network\\somelocation", 
    @"\\\my-network\somelocation", @"my-network\somelocation",
     @"\\my-network\\somelocation",@"\\my-network\somelocation\aa\dd",
     @"\\my-network\somelocation\",@"\\my-network\\somelocation"};
foreach (string name in names)
{
 if (Regex.IsMatch(name, pattern))
 {
  Console.WriteLine(name);
   //Directory.Exists function to check if file exists
 }
}   

Answer 10

Alexander's Answer + Relative Paths

Alexander has the most correct answer thus far since it supports spaces in file names (i.e. C:\Program Files (x86)\ will match)... This aims to include relative paths as well.

For example, you can do cd / or cd \ and it does the same thing.

Further more, if you're currently in C:\some\path\to\some\place and you type either of those commands, you end up at C:\

Even more, you should consider paths, that start with '/' as a root path (to the current drive).

(?:[a-zA-Z]:(\|/)|file://|\\|.(/|\)|/)([^,\/:*\?\<>\"\|]+(\|/){0,1})

A Modified version of Alexander's answer, however, we include paths that are relative with no leading / or drive letter, as well as / with no leading drive letter (relative to the current drive as root).