Services
Technology Web App Development Mobile App Development Windows App Development Database Development UI/UX Development Cloud Development SEO Digital Marketing Guest Posting Content Writing Artificial Intelligence Data Science ERP Development CRM Development CMS Development LMS Development Business Listing Blockchain Technology Startup Promotion AI Tools Integration
Products
Data Converter Cleaner TUC - Unit Converter Import Export Survey Manager Tweet Controller
Developer
Article Blog Forum Interview Beginner News Startup Quiz
Users
Career
Apply Job Internship
Pricing
Login Sign Up Get a Quote

interview

Home Interviews How can you read a file while it is being written to by another process? – MindStick
Ask Question

1 Answers

ICSM Computer
ICSM Computer 12 May 2025
Report Abuse

To read a file while it is being written to by another process in C#, you need to open it with shared read access. This lets your code read from the file even if another process has it open for writing — assuming that process allows sharing.

Example: Open file with shared access

using System;
using System.IO;
using System.Text;

class Program
{
    static void Main()
    {
        string path = @"C:\Logs\active.log";

        try
        {
            using (var stream = new FileStream(
                path,
                FileMode.Open,
                FileAccess.Read,
                FileShare.ReadWrite)) // <-- allow reading even if another process is writing
            using (var reader = new StreamReader(stream, Encoding.UTF8))
            {
                string content = reader.ReadToEnd();
                Console.WriteLine(content);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine("Error reading file: " + ex.Message);
        }
    }
}

Key Points:

Option Meaning
FileAccess.Read You're only reading the file
FileShare.ReadWrite Allows other processes to read/write while you read
FileMode.Open Open the file (throws if it doesn't exist)

This works only if the other process opens the file with a compatible sharing mode.

Tip for reading tailing logs:

If the file is being appended to (like a log), you can use a while loop to poll for new content, similar to tail -f.

MindStick Training
Markdown for AI

A clean, structured version of this page for AI assistants and LLMs.

Open .md