Parse filename from full path using regular expressions in C#

Question

How do I pull out the filename from a full path using regular expressions in C#?

Say I have the full path C:\CoolDirectory\CoolSubdirectory\CoolFile.txt.

How do I get out CoolFile.txt using the .NET flavor of regular expressions? I'm not really good with regular expressions, and my RegEx buddy and me couldn't figure this one out.

Also, in the course of trying to solve this problem, I realized that I can just use System.IO.Path.GetFileName, but the fact that I couldn't figure out the regular expression is just making me unhappy and it's going to bother me until I know what the answer is.

It's fine you want to know how it would work with regular expressions, but to make this world a better place, please promise that you'll use Path.* anyway :) — OregonGhost
– OregonGhost, Commented Oct 21, 2008 at 19:38
GetFileName may not be an option if you are working with Long Path — Ufuk Hacıoğulları
– Ufuk Hacıoğulları, Commented Jun 9, 2012 at 22:40
There are reasons for and against regex: codinghorror.com/blog/2008/06/… — benPearce
– benPearce, Commented Jul 9, 2012 at 0:29

Peter Mortensen · Accepted Answer · 2010-03-08 14:03:16Z

40

Why must you use regular expressions? .NET has the built-in Path.GetFileName() method specifically for this which works across platforms and filesystems.

edited Mar 8, 2010 at 14:03

Peter Mortensen

31.4k22 gold badges110 silver badges134 bronze badges

answered Oct 21, 2008 at 19:33

Dour High Arch

21.8k31 gold badges78 silver badges93 bronze badges

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

3 Comments

Kon Over a year ago

You didn't read the question carefully. He's aware of GetFileName(), but wants to know how to do it with reg ex.

Dour High Arch Over a year ago

When I posted my answer that sentence was not there.

Kon Over a year ago

Then feel free to ignore me. :)

Brian Dukes · Accepted Answer · 2008-10-21 20:18:42Z

21

//  using System.Text.RegularExpressions;

/// <summary>
///  Regular expression built for C# on: Tue, Oct 21, 2008, 02:34:30 PM
///  Using Expresso Version: 3.0.2766, http://www.ultrapico.com
///  
///  A description of the regular expression:
///  
///  Any character that is NOT in this class: [\\], any number of repetitions
///  End of line or string
///  
///
/// </summary>
public static Regex regex = new Regex(
      @"[^\\]*$",
    RegexOptions.IgnoreCase
    | RegexOptions.CultureInvariant
    | RegexOptions.IgnorePatternWhitespace
    | RegexOptions.Compiled
    );

UPDATE: removed beginning slash

edited Oct 21, 2008 at 20:18

answered Oct 21, 2008 at 19:34

Brian Dukes

157k25 gold badges152 silver badges176 bronze badges

2 Comments

dlamblin Over a year ago

You realize that's going to get "\CoolFile.txt"

Brian Dukes Over a year ago

Good catch, didn't cross my mind that the slash wasn't supposed to be there when I tested it

Seth Petry-Johnson · Accepted Answer · 2008-10-21 19:35:14Z

7

Here's one approach:

string filename = Regex.Match(filename, @".*\\([^\\]+$)").Groups[1].Value;

Basically, it matches everything between the very last backslash and the end of the string. Of course, as you mentioned, using Path.GetFileName() is much easier and will handle lots of edge cases that are a pain to handle with regex.

answered Oct 21, 2008 at 19:35

Seth Petry-Johnson

12.1k7 gold badges52 silver badges70 bronze badges

1 Comment

Joe Internet Over a year ago

+1 because I was able to solve a Perl regex issue with it. Thanks.

Peter Mortensen · Accepted Answer · 2010-03-08 13:59:30Z

7

Shorter:

string filename = Regex.Match(fullpath, @"[^\\]*$").Value;

Or:

string filename = Regex.Match(fullpath, "[^\\"+System.IO.Path.PathSeparator+"]*$").Value;

Without Regex:

string[] pathparts = fullpath.Split(new []{System.IO.Path.PathSeparator});
string file = pathparts[pathparts.Length-1];

The official library support you mentioned:

string file = System.IO.Path.GetFileName(fullpath);

edited Mar 8, 2010 at 13:59

Peter Mortensen

31.4k22 gold badges110 silver badges134 bronze badges

answered Oct 21, 2008 at 19:43

dlamblin

45.6k22 gold badges105 silver badges144 bronze badges

Comments

Jeff Yates · Accepted Answer · 2008-10-21 19:35:54Z

1

\w+:\\(\w+\\)*(?<file>\w*\.\w*)

This obviously would need expanding to cover all path characters, but the named group "file" contains your filename for the example path given.

answered Oct 21, 2008 at 19:35

Jeff Yates

62.6k20 gold badges144 silver badges193 bronze badges

2 Comments

Artur Ampilogov Over a year ago

just curious, what does next group do? (?<file>\w*\.\w*). should it be (?: )

Jeff Yates Over a year ago

@Artu: (?<file>\w*\.\w*) is a named capture group.

Jonathan C Dickinson · Accepted Answer · 2008-10-22 05:31:48Z

0

You should rather use the System.Path class. It will mean you will have to worry about less if you ever decide to support Mono/Linux (dlamblin's example takes the path seperator into account, but you may get a strange OS that has strange paths). The System.Path class can also combine two paths into one. So for example:

Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "My App Stuff");

would resolve to:

Windows: C:\Documents and Settings\[User]\My Documents\My App Stuff
Linux: /[User]/My App Stuff

answered Oct 22, 2008 at 5:31

Jonathan C Dickinson

7,3114 gold badges39 silver badges46 bronze badges

Collectives™ on Stack Overflow

Parse filename from full path using regular expressions in C#

6 Answers 6

3 Comments

2 Comments

1 Comment

Comments

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

3 Comments

2 Comments

1 Comment

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related