Replacing / removing specific part of file names using regex

Question

I'm new to C# and need to loop through a directory and remove the last part of any and all files that end in _xxxxxx.xml (an underscore followed by 6 digits).

For example, the filename filename_A_123_456789.xml becomes filename_A_123.xml .

What I have so far:

private static void RenameFiles(string outputPath)
{
    DirectoryInfo d = new DirectoryInfo(outputPath);
    FileInfo[] infos = d.GetFiles();
    foreach (FileInfo f in infos)
    {
        string newName = Regex.Replace(f.FullName, "(\\[_\d]\\s)", temp);

        File.Move(f.FullName, newName);
    }
}

But that's not working. Ang CSharp Regexxers out there?

Answer 1

You can use the regex:

_\d{6}(\.[^.]+)$

and replace with $1 instead.

The regex is matching 6 digits, then group 1 ( (\.[^.]+) ) matches the extension, which you replace with in the replacement string. The extension is matched by "a dot followed by a bunch of non-dots". Also note that the end of string anchor $ to assert that all of this must be at the end of the string.

Change your code to:

string newName = Regex.Replace(f.FullName, @"_\d{6}(\.[^.]+)$", "$1");

Answer 2

A regex is fine for your need. As an alternative, here is a regex free solution if you want to use one:

public static void Main()
{
    var source = @"filename_A_123_456789.xml";
    var slices =  Path.GetFileNameWithoutExtension(source).Split('_');
    var last = slices.Last();
    var isSpecific = last.Length == 6 && last.All(char.IsDigit);
    var result = string.Join("_", isSpecific ? slices.Take(slices.Length - 1) : slices) + Path.GetExtension(source);
    Console.WriteLine(result);
}

• We split the name by '_'
• We take the last section
• We define if the last section is a specific part
• We concat back everthing minus the last one if it is a specific part

Try it Online!

Answer 3

Your regex doesn't quantify the \d in any way to define that you are looking for 6 digits to be exact.

Use this instead:

(\S*)_\d{6}(\.xml) /m

This regex captures all non-whitespace characters before the _ followed by six digits, and the extension .xml into two separate capturing groups.

Then replace with $1$2 , group 1 followed by group 2.

Demo

Answer 4

Just try:

string newName = Regex.Replace(f.FullName, "(\\_\\d{6}\\.xml)", ".xml");