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Home Interviews How do you backup a file before editing and automatically restore it if the operation fails? – MindStick
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1 Answers

ICSM Computer
ICSM Computer 18 May 2025
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To back up a file before editing and automatically restore it if the operation fails, follow this common pattern:

Pattern: Backup → Try Edit → On Failure → Restore

  1. Copy the original file to a backup location
  2. Attempt the edit operation
  3. On exception, restore from backup
  4. On success, optionally delete the backup

C# Example

using System;
using System.IO;

public class SafeFileEditor
{
    public static void EditFileSafely(string originalPath, Action<string> editAction)
    {
        string backupPath = originalPath + ".bak";

        try
        {
            // Step 1: Backup
            File.Copy(originalPath, backupPath, overwrite: true);

            // Step 2: Try the edit
            editAction(originalPath);

            // Step 3: Delete backup after successful edit
            if (File.Exists(backupPath))
                File.Delete(backupPath);
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Error: {ex.Message}");

            // Step 4: Restore from backup
            if (File.Exists(backupPath))
            {
                File.Copy(backupPath, originalPath, overwrite: true);
                Console.WriteLine("Original file restored from backup.");
            }
        }
    }
}

Example Usage

SafeFileEditor.EditFileSafely("data.txt", path =>
{
    // Example: Append some text
    File.AppendAllText(path, "\nUpdated on " + DateTime.Now);
});

Tips for Safety

  1. Use a .bak, .backup, or timestamped suffix for the backup file.
  2. Make sure backup and restore operations handle IOException (file in use, permission denied).
  3. For large or critical files, consider copying to another disk or making a zip snapshot.
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