Appending a line to a hosts file ONLY if it doesnt already exist

Question

My code looks like this;

using (StreamWriter w = File.AppendText(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "drivers/etc/hosts")))
{
    w.WriteLine("127.0.0.1 www.google.com");
}

I want get rid of duplicates in hosts file. How can I check if line exists and prevent appending it again?

Do you want to get rid of existing duplicates or just prevent creating new duplicates? — derpirscher, May 04 '16 at 12:40

score 1 · Answer 1 · answered May 04 '16 at 12:20

You can use this little LINQ query to check if there's already a line:

bool exists = File.ReadLines(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "drivers/etc/hosts"))
    .Any(l => l == "127.0.0.1 www.google.com");
if(!exists)
    w.WriteLine("127.0.0.1 www.google.com");

score 1 · Accepted Answer · answered May 04 '16 at 12:26

May be a simple solution:
Just read all the text and check for the presence of your text. If not write to the file.

string texttowrite = "127.0.0.1 wwwgoogle.com";
string text = File.ReadAllText(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "drivers/etc/hosts"), Encoding.UTF8);
if (!text.Contains(texttowrite))
{
    using (StreamWriter w = File.AppendText(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "drivers/etc/hosts")))
    {
        w.WriteLine(texttowrite);
    }
}

1

it works very well, thank you – Wiii May 04 '16 at 13:18

Appending a line to a hosts file ONLY if it doesnt already exist

2 Answers2