Develop Reference

Confused about Directory.GetFiles

I've read the docs about the Directory.GetPath search pattern and how it is used, because I noticed that *.dll finds both test.dll and test.dll_20170206. That behavior is documented
Now, I have a program that lists files in a folder based on a user-configured mask and processes them. I noticed that masks like *.txt lead to the above mentioned "problem" as expected.
However, the mask fixedname.txt also causes fixedname.txt_20170206 or the like to appear in the list, even though the documentation states this only occurs
When you use the asterisk wildcard character in a searchPattern such as "*.txt"
Why is that?
PS: I just checked: Changing the file mask to fixednam?.txt does not help even though the docs say
When you use the question mark wildcard character, this method returns only files that match the specified file extension. For example, given two files, "file1.txt" and "file1.txtother", in a directory, a search pattern of "file?.txt" returns just the first file, whereas a search pattern of "file*.txt" returns both files.

If you need a solution you may transform the filter pattern into a regular expression by replacing * by (.*) and ? by .. You also have to escape some pattern characters like the dot. Then you check each filename you got from Directory.GetFiles against this regular expression. Keep in mind to not only check if it is a match but that the match length is equal to the length of the filename. Otherwise you get the same results as before.

GetFiles uses pattern serach, it searches for all names in path ending with the letters specified.
You can write code similar to below to get only .txt extension file
foreach (string strFileName in Directory.GetFiles(#"D:\\test\","*.txt"))
{
string extension;
extension = Path.GetExtension(strFileName);
if (extension != ".txt")
continue;
else
{
//processed the file
}
}

How to use GetFiles() search to include doc files but excude docx files?

Currently I am looping through my file system like this
For Each filename As String In Directory.GetFiles(sourceFolder, "*.doc")
However this is including docx files to the list of files that GetFiles returns. I wish to only search for doc files and not docx. Any idea if there is a truncate or stop search character I can use in the search pattern?

This is the default behaviour of GetFiles, you can use LINQ to do further filtering.
var files = Directory.GetFiles(#"C:\test", "*.doc")
.Where(file=> file.EndsWith(".doc", StringComparison.CurrentCultureIgnoreCase))
.ToArray();//If you want an array back
Directory.GetFiles Method (String, String)
When you use the asterisk wildcard character in a searchPattern such
as "*.txt", the number of characters in the specified extension
affects the search as follows:
If the specified extension is exactly three characters long, the method returns files with extensions that begin with the specified extension. For example, "*.xls" returns both "book.xls" and "book.xlsx".

Given the fact that you want to iterate over your files and considering the default behavior of these methods I suggest to use EnumerateFiles instead of GetFiles. In this way you could add a simple check on the extension of the current file
foreach(string filename in Directory.EnumerateFiles(sourceFolder, "*.doc"))
{
if(!filename.EndsWith("x", StringComparison.CurrentCultureIgnoreCase))
{
.....
}
}
Not elegant as the Linq only solution but still working and not creating an array of all the filenames present in the directory

I am not a C# programmer so may be there can be syntax mistake, but i think it may solve your problem.
foreach (FileInfo fi in di.GetFiles("*.doc")
.Where(fi => string.Compare(".doc", fi.Extension,
StringComparison.OrdinalIgnoreCase) == 0))
{
myFiles.Add(fi);
}

Find files using wild card in C#

I am trying to find files from a directory:
String[] search1 = Directory.GetFiles(voiceSource, "85267-*.wav")
.Select(path => Path.GetFileName(path))
.ToArray();
String[] search2 = Directory.GetFiles(voiceSource, "85267 *.wav")
.Select(path => Path.GetFileName(path))
.ToArray();
But in search1, it selects both 85267-s.wav and 85267 -s.wav. But I want only 85267-s.wav to be selected.
search2 is doing well.
How can I do that?

The behaviour you are experiencing is because of short file name. Since you will get 85267-~1.WAV for 85267 -s.wav and since that matches your wild card "85267-*.wav" you get both files back.
The is explained in Directory.GetFiles Method (String, String)
Because this method checks against file names with both the 8.3 file
name format and the long file name format, a search pattern similar
to "1.txt" may return unexpected file names. For example, using a
search pattern of "1.txt" will return "longfilename.txt" because the
equivalent 8.3 file name format would be "longf~1.txt".
For workaround you can use Directory.EnumerateFiles to first select both files matching your criteria and then compare the actual(long) file name part using StartsWith. Remember EnumerateFiles does lazy evaluation.
String[] search1 = Directory.EnumerateFiles(#"C:\test", "85267-*.wav")
.Where(file => Path.GetFileName(file).StartsWith("85267-"))
.Select(path => Path.GetFileName(path))
.ToArray();

Yes, this is a side-effect of the MS-Dos 8.3 short name support that's still turned on today on most file systems. Something you can see with the DIR /X command, it displays those short names. On my machine:
C:\temp>dir /x *.wav
01/21/2015 09:11 AM 6 85267-~1.WAV 85267 -s.wav
01/21/2015 09:11 AM 6 85267-s.wav
2 File(s) 12 bytes
0 Dir(s) 235,121,160,192 bytes free
Note how the short name for "85267 -s" is missing the space. It is not a valid character in a short name. What's left over now also matches your wildcard.
That's not where the trouble ends with those short names, A wildcard like *.wav will also match a file like foobar.wavx, a completely different file type.
Short-name generation is, frankly, a relic from the previous century that ought to be turned off today. But that is not typically anything you can control yourself. You have to deal with these accidental matches and double-check what you get back. With a Regex for example.

List files in folder which match pattern

I need to list files in directory which match some pattern.
I tried playing with Directory.GetFiles, but don't fully
get why it behaves in some way.
1) For example, this code:
string[] dirs = Directory.GetFiles(#"c:\test\", "*t");
foreach (string dir in dirs)
{
Debugger.Log(0, "", dir);
Debugger.Log(0, "", "\n");
}
outputs this:
c:\test\11.11.2007.txtGif
c:\test\12.1.1990.txt
c:\test\2.tGift
c:\test\2.txtGif
c:\test\test.txt
...others hidden
You can see some files end with f but were still returned by query, why?
2) Also, this:
string[] dirs = Directory.GetFiles(#"c:\test\", "*.*.*.txt");
foreach (string dir in dirs)
{
Debugger.Log(0, "", dir);
Debugger.Log(0, "", "\n");
}
returns this:
c:\test\1.1.1990.txt
c:\test\1.31.1990.txt
c:\test\12.1.1990.txt
c:\test\12.31.1990.txt
But according to the documentation (http://msdn.microsoft.com/en-us/library/07wt70x2(v=vs.110).aspx) I think it had to return also
this file which is in the directory:
11.11.2007.txtGif
since extension (in the query string) is 3 letters long, but it didn't. why?
(when query extension is 3 letters long, doc says it will return extensions which start with specified extensions too, e.g., see Remarks).
Am I the only one who finds these results strange?
Is there any other approach you would recommend for using when one wants to list files in folder which match certain pattern?
User in my case may arbitrarily type some pattern, and I don't want to rely on
method which I am unsure about the result (like it happened with GetFiles).

This is the way that the Windows API works - you will see the same results if you use the dir command in a command prompt. This does NOT use regular expressions! It's pretty obscure...
If you want to do your own filtering, you can do it like so:
var filesEndingInT = Directory.EnumerateFiles(#"c:\test\").Where(f => f.EndsWith("t"));
If you want to use regular expressions to match, you can do it thusly:
Regex regex = new Regex(".*t$");
var matches = Directory.EnumerateFiles(#"c:\test\").Where(f => regex.IsMatch(f));
I suspect that you will want to let the user type in a simplified form of pattern and turn it into a regular expression, e.g.
"*.t" -> ".*t$"
The regular expression to find all filenames ending in t is ".*t$":
.*t$
Debuggex Demo

All of this behavior is exactly as described in the documentation you've linked. Here's an excerpt of the pertinent bits:
When you use the asterisk wildcard character in a searchPattern such
as "*.txt", the number of characters in the specified extension
affects the search as follows:
If the specified extension is exactly three characters long, the method returns files with extensions that begin with the specified
extension. For example, "*.xls" returns both "book.xls" and
"book.xlsx".
In all other cases, the method returns files that exactly match the specified extension. For example, "*.ai" returns "file.ai" but not
"file.aif".
When you use the question mark wildcard character, this method returns
only files that match the specified file extension. For example, given
two files, "file1.txt" and "file1.txtother", in a directory, a search
pattern of "file?.txt" returns just the first file, whereas a search
pattern of "file*.txt" returns both files. NoteNote
Because this method checks against file names with both the 8.3 file
name format and the long file name format, a search pattern similar to
"1.txt" may return unexpected file names. For example, using a
search pattern of "1.txt" returns "longfilename.txt" because the
equivalent 8.3 file name format is "LONGFI~1.TXT".
http://msdn.microsoft.com/en-us/library/wz42302f%28v=vs.110%29.aspx
The last paragraph above clearly explains your results when searching for *t. You can see this by using the command dir C:\test /x to show the 8.3 filenames. Here, C:\test\11.11.2007.txtGif matches *t because its 8.3 filename is 111120~1.TXT.
For the treatment of *.*.*.txt, I think you're either mis-interpreting the first bit about three-letter file extensions or perhaps it wasn't written quite clearly. Note that they quite specifically mentioned wildcard usage 'in a searchPattern such as "*.txt"'. Your search pattern doesn't match that, so you have to read between the lines a bit to see why their comment about three-letter file extensions applies to the example they gave but not yours. Really, I think that whole top section can be ignored if you just put a bit of thought into the last bit about 8.3 filenames. The treatment of three-letter file extensions after wildcards is really just a side-effect of the 8.3 filename search behavior.
Consider the examples they gave:
"*.xls" returns both "book.xls" and "book.xlsx"
This is because the filename for "book.xls" (both 8.3 and long filename, since the name naturally complies with 8.3) and the 8.3 filename for "book.xlsx" ("BOOK~1.XLS") matches a query of "*.xls".
"*.ai" returns "file.ai" but not "file.aif"
This is because "file.ai" naturally matches "*.ai" while "file.aif" doesn't. 8.3 search behavior doesn't come into play here at all, because both filenames are already 8.3-compliant. However, even if they weren't, the same would still hold true because any 8.3 filename for a file with an extension of ".ai" is still going to end in just ".AI".
The only reason it matters whether or not the file extension in your search is exactly three characters is because the 8.3 filenames are included in the search, and 8.3 filname extensions for objects with long filenames will always have just the first three characters after the last dot in the long filename. The key part missing from the documentation above is that the "first three characters" matching is done only against the 8.3 filename.
So, let's look at the anomalies you're asking about here. (If you want any other strange behaviors explained, beyond your results for *.t and *.*.*.txt, please post them as separate questions.)
TL;DR:
Output of a search for *t includes 11.11.2007.txtGif and 2.txtGif.
This is because the 8.3 filenames match a pattern of *t.
11.11.2007.txtGif = 111120~1.TXT
2.txtGIF = 2BEFD~1.TXT
(Both 8.3 filenames end in "T".)
Output of a search for *.*.*.txt does not include 11.11.2007.txtGif.
This is because neither the long filename, nor the 8.3 filename, match a pattern of *.*.*.txt.
11.11.2007.txtGif = 111120~1.TXT
(The long filename doesn't match because it doesn't end in ".txt", and the 8.3 filename doesn't match because it only has one dot.)

https://learn.microsoft.com/en-us/dotnet/api/system.io.directoryinfo.getfiles?view=netframework-4.5
The above Microsoft documentation is wrong as usual,
it says this code:
DirectoryInfo di = new DirectoryInfo(#"C:\Users\tomfitz\Documents\ExampleDir");
Console.WriteLine("No search pattern returns:");
Console.WriteLine();
Console.WriteLine("Search pattern *2* returns:");
foreach (var fi in di.GetFiles("*2*"))
{
Console.WriteLine(fi.Name);
Console.WriteLine(fi.Fullname); // this reveals the bug
}
should return the following but it does not
It still matches against the whole file path not just the filename.
Search pattern *2* returns:
log2.txt
test2.txt

Find file by name and unknown extension C#

Are there any clever ways to easily find a file by its name and unknown extension in C#?
I have a image folder with images of different types .jpg, .gif and .png.
And all the program knows is the name of the image, and not the extension.
Is it possible to get the file by its name, without doing some big recursive resource consuming loop?

You could use the EnumerateFiles method and specify a search pattern:
var files = Directory.EnumerateFiles(#"c:\work", "somefilename.*");
This will of course return an IEnumerable<string> of all files that match this search pattern. If you know there can only be one, or wanted to get the first in the list, just chain it with LINQ to further filter the results.

Yes, it is possible. Use overloaded Directory.GetFiles method which accepts search pattern as second parameter:
string[] files = Directory.GetFiles(#"c:\images", fileName + ".*");

Linq to rescue
var filenames = Directory.GetFiles(#"C:\Windows\System32").Select(f => Path.GetFileName(f)).Where(fn => fn.StartsWith("ap"));
Let linq do the looping and filtering for you

There is a couple of options:
Build your file index in advance (simple dictionary will do the
trick).
Use windows search API.
Use EnumerateFiles, altough performance wise this is similar to a bit optimized big recursion traverse.