Capturing nslookup shell output with C#
https://stackoverflow.com/questions/353601
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I have a command-line process I would like to automate and capture in C#.
At the command line, I type:
nslookup
This launches a shell which gives me a > prompt. At the prompt, I then type:
ls -a mydomain.local
This returns a list of local CNAMEs from my primary DNS server and the physical machines they are attached to.
What I would like to do is automate this process from C#. If this were a simple command, I would just use Process.StartInfo.RedirectStandardOutput = true, but the requirement of a second step is tripping me up.
Solution
ProcessStartInfo si = new ProcessStartInfo("nslookup");
si.RedirectStandardInput = true;
si.RedirectStandardOutput = true;
Process nslookup = new Process(si);
nslookup.Start();
nslookup.StandardInput.WriteLine("ls -a mydomain.local");
nslookup.StandardInput.Flush();
// use nslookup.StandardOutput stream to read the result.
OTHER TIPS
Not what you asked, but I once wrote an app that did what you're doing. I eventually moved to using a .NET library to do the DNS lookups, which turned out to be a lot faster.
I'm pretty sure I used this library from the CodeProject site.
I know this is an old one, but still like to contribute. I used the shell output from "NsLookup Hostname Server" to get the IPv4 addresses from a computername in our domain and strip out any other information like DNS server / ipv6 addresses..
This is kinda quickly done but it works, there is also a failover added if the shell fails that you would use the built in nslookup method from C#.
it is rather long but it gave me the possibility to read the ipv4 from the shell without using an external library or without using the built in nslookup function as it does allow to choose the dns server.
If you are wondering about the if loops in the middle, there might be more elegant solutions but for my personal use, this worked out quite well, most hosts in our domain returned 2 ipv6 and 2 ipv4, therefore, it test up to 4 times.
Hope this can help..
private void button1_Click(object sender, EventArgs e)
{
IPAddress[] ips = NsLookup(computername, dnsserver);
txtResult.Text = string.Empty;
if (ips != null)
{
txtResult.Text = ips[0].ToString();
txtResult.Text += Environment.NewLine;
if (ips[1] != null)
{
txtResult.Text += ips[1].ToString();
}
else
{
}
}
else
{
txtResult.Text = "No IP found";
}
}
public IPAddress[] NsLookup(string computername, string domaincontroller)
{
IPAddress[] ips = new IPAddress[2];
try
{
// Creating streamreaders to read the output and the errors
StreamReader outputReader = null;
StreamReader errorReader = null;
string nslookup = @"C:\Windows\System32\Nslookup.exe";
try
{
// Setting process startupinfo
ProcessStartInfo processStartInfo = new ProcessStartInfo(nslookup, computername + " " + domaincontroller);
processStartInfo.ErrorDialog = false;
processStartInfo.UseShellExecute = false;
processStartInfo.RedirectStandardError = true;
processStartInfo.RedirectStandardInput = true;
processStartInfo.RedirectStandardOutput = true;
processStartInfo.WindowStyle = ProcessWindowStyle.Minimized;
// Starting Process
Process process = new Process();
process.StartInfo = processStartInfo;
bool processStarted = process.Start();
if (processStarted)
{
// Catching the output streams
outputReader = process.StandardOutput;
errorReader = process.StandardError;
string errorresult = errorReader.ReadLine();
errorReader.Close();
if (errorresult != null)
{
// Failure got thrown in NsLookup Streamreading, try build-in Method
try
{
ips = Dns.GetHostAddresses(computername);
return ips;
}
catch
{
return null;
}
}
else
{
// Clearing out all the values before the addresses.
outputReader.ReadLine();
outputReader.ReadLine();
outputReader.ReadLine();
outputReader.ReadLine();
// Reading and Verifying the first outputline (the address is found after "Addresses: ") - 2 part of the array is taken (after second space)
string outputline = outputReader.ReadLine();
string[] outputlineaftersplit = outputline.Split(' ');
string ipfortesting = outputlineaftersplit[2].Trim();
if (verifyIP(ipfortesting) != null) // First entry is ipv4
{
ips[0] = verifyIP(ipfortesting);
outputline = outputReader.ReadLine();
ipfortesting = outputline.Trim();
if (verifyIP(ipfortesting) != null) // First and second entry are ipv4
{
ips[1] = verifyIP(ipfortesting);
return ips;
}
else
{
return ips;
}
}
else
{
outputline = outputReader.ReadLine();
ipfortesting = outputline.Trim();
if (verifyIP(ipfortesting) != null)
{
ips[0] = verifyIP(ipfortesting);
outputline = outputReader.ReadLine();
ipfortesting = outputline.Trim();
if (verifyIP(ipfortesting) != null)
{
ips[0] = verifyIP(ipfortesting);
outputline = outputReader.ReadLine();
ipfortesting = outputline.Trim();
if (verifyIP(ipfortesting) != null)
{
ips[1] = verifyIP(ipfortesting);
return ips;
}
else
{
return ips;
}
}
else
{
return ips;
}
}
else
{
outputline = outputReader.ReadLine();
ipfortesting = outputline.Trim();
if (verifyIP(ipfortesting) != null)
{
ips[0] = verifyIP(ipfortesting);
outputline = outputReader.ReadToEnd();
ipfortesting = outputline.Trim();
if (verifyIP(ipfortesting) != null)
{
ips[1] = verifyIP(ipfortesting);
return ips;
}
else
{
return ips;
}
}
else
{
ips = null;
return ips;
}
}
}
}
}
else
{
// Failure got thrown in NsLookup Streamreading, try build-in Method
try
{
ips = Dns.GetHostAddresses(computername);
return ips;
}
catch
{
return null;
}
}
}
catch
{
System.Windows.Forms.MessageBox.Show("ERROR 1");
// Failure got thrown in NsLookup Streamreading, try build-in Method
try
{
ips = Dns.GetHostAddresses(computername);
return ips;
}
catch
{
return null;
}
}
finally
{
if (outputReader != null)
{
outputReader.Close();
}
}
}
catch
{
System.Windows.Forms.MessageBox.Show("ERROR 2");
// Failure got thrown in NsLookup Streamreading, try build-in Method
try
{
ips = Dns.GetHostAddresses(computername);
return ips;
}
catch
{
return null;
}
}
}
public IPAddress verifyIP(string ipfromreader)
{
IPAddress ipresult = null;
bool isIP = IPAddress.TryParse(ipfromreader, out ipresult);
if (isIP && (ipresult.AddressFamily != AddressFamily.InterNetworkV6))
{
return ipresult;
}
else
{
return null;
}
}
}
}
