Get string (file name) of a given extension from within a text file

Question

I apologize if the question title is a little confusing, but let's say a text file contains the following data:

Sample         'Line1
 1             'Line2
 2             'ProjectCount
FileA.ext      'Projects( 1)
 0             'SortTermCount
FileB.ext      'Projects( 2)
 0             'SortTermCount
 ...

I know the extension name that exists as a string within the file (i.e. .doc), what I would like to do is get the full name and the extension of the file, the code would return "FileA.ext" and "FileB.ext" (as a string, or array (preferably), or whatever).

I tried to modify code from this SO question: https://stackoverflow.com/a/3152180 to work with text files, but I guess that is only for directories.

EDIT: The value before 'ProjectCount' tell me how many extension files I can expect, so perhaps I don't need to search the entire file?

Is the filename always in the beginning of the line, followed by space? — Alioza, Jun 12 '15 at 16:15
@Alioza From looking at various files, it appears to be that way. So would I just read line by line, split it up, and check if the first index is an extension file? Is there a faster way? — Mohammad Ali, Jun 12 '15 at 16:20
@DavidG the numbers begin with a space, but regular text starts without a space. — Mohammad Ali, Jun 12 '15 at 16:21

DavidG · Answer 1 · 2015-06-12T16:36:46.233

1

You could do it like this:

var fileName = @"C:\source.txt";
var files = File
    .ReadAllLines(fileName)
    .Where(line => !line.StartsWith(" "))
    .Skip(1) //Ignore the first line
    .Select(line => line.Substring(0, line.IndexOf(" ")));

Now files contains an IEnumerable<string> containing all of your file names.

So you can loop through the filenames like this:

foreach(string fileName in files)
{
    //fileName is a string variable

}

edited Jun 12 '15 at 16:36

answered Jun 12 '15 at 16:24

DavidG

113,891
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Should I change first var to string, and second to an array of strings? – Mohammad Ali Jun 12 '15 at 16:29
You could change first `var` to `string` and the second to `IEnumerable` but there's no need. – DavidG Jun 12 '15 at 16:31
How will I get an output/access to the file names? – Mohammad Ali Jun 12 '15 at 16:34
I've added an example, it's just a simple loop, or you could convert it to a string array with `files.ToArray()` – DavidG Jun 12 '15 at 16:37
With your code, I get the file names, but it also prints some extra stuff: FileA.ext FileB.ext FileC.ext FileD.ext default default default default none False False False False – Mohammad Ali Jun 12 '15 at 16:46
Perhaps because you are printing the first index of lines without spaces, instead of the extension files? – Mohammad Ali Jun 12 '15 at 16:51
If you can modify your code to add the extension check, while still keeping the code clean (like now), your answer will be selected as it is currently the cleanest. – Mohammad Ali Jun 12 '15 at 17:34

Alioza · Accepted Answer · 2015-06-12T17:04:25.453

1

If you know the extensions that can show up you can use the following solution with a regex:

//regex for file name with known extensions    
Regex r = new Regex("^.*\\.(ext|doc|PUT_OTHER_EXTENSIONS_HERE)$");
var lines = File.ReadAllLines(FILE_PATH);
var res = lines.Where(x => !string.IsNullOrWhiteSpace(x) && r.Match(GetFirstEntry(x)).Success)
                    .Select(x => GetFirstEntry(x));

where GetFirstEntry :

            /// <summary>
            /// Splits the string by the "'" char and gets the first entry.
            /// </summary>
            /// <param name="x"></param>
            /// <returns></returns>
            private static string GetFirstEntry(string x)
            {
             try{
                return x.Split(new string[] { "'" }, StringSplitOptions.RemoveEmptyEntries)[0].Trim();
                }catch{return string.Empty;}
            }

edited Jun 12 '15 at 17:04

answered Jun 12 '15 at 16:28

Alioza

1,690
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For last line (Select.(x.Split...)), it says 'x' does not exist in current context. – Mohammad Ali Jun 12 '15 at 16:37
Is there a way we can make this code more readable (similar to David's, but I guess some regex can get dirty)? :D If not, perhaps add some comments? – Mohammad Ali Jun 12 '15 at 16:52
You should have kept your first answer as well. Currently it says lines is not in the context. – Mohammad Ali Jun 12 '15 at 17:01

score 0 · Answer 3 · edited May 23 '17 at 10:26

You can do:

Use File.ReadLines to read each file line by line, instead of loading everything in the memory
Split each line on white space character
Consider first column of split as possible file name
Use Path.GetExtension method to get file's extension
Compare it against your extensionToCheck with ignoring case
Select those matching

Like:

string extensionToCheck = ".ext";
string filePath = @"test.txt";
var fileNames = File.ReadLines(filePath)
    .Select(line => new {PossibleFile = line.Split().First()})
    .Where(p =>
        Path.GetExtension(p.PossibleFile)
            .Equals(extensionToCheck, StringComparison.InvariantCultureIgnoreCase))
    .Select(f => f.PossibleFile);

For output use:

foreach (var fileName in fileNames)
{
    Console.WriteLine(fileNames);
}

In case of above sample file you will get two records

FileA.ext
FileB.ext

Could you add some comments to the code? Edit: I think the ones at the top are sufficient :) — Mohammad Ali, Jun 12 '15 at 16:56
@MohammadAli, each step is explained in the bullets before, If you have any particular question about a particular part of code then ask — Habib, Jun 12 '15 at 16:57

Get string (file name) of a given extension from within a text file

3 Answers3