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In-place file regex replacement

, 1 Feb 2008 CPOL
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A function to apply a regex replacement to a file.


This is a basic function for editing a file in-place, applying a Regex and a replacement string to each line.

Using the code

Here's the code:

using System.Text.RegularExpressions;

public static void ApplyRegexToFile(string filename,
        Regex match, string replacement)
    string temp = Path.GetTempFileName();
    using (StreamReader sr =
        new StreamReader(File.Open(filename, FileMode.Open)))
    using (StreamWriter sw =
        new StreamWriter(File.Open(temp, FileMode.Append)))
        string line;
        while ((line = sr.ReadLine()) != null) {
            line = match.Replace(line, replacement);
    File.Move(temp, filename);

Here's an example of how it might be used:

ApplyRegexToFile(@"c:\Program Files\SomeProgram\SomeConfigFile",
                 new Regex(@"(someconfigsetting)=([a-z]*)", RegexOptions.IgnoreCase),


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Mike McCabe

United States United States
No Biography provided

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