C# Console receive input with pipe

Question

I know how to program Console application with parameters, example : myProgram.exe param1 param2.

My question is, how can I make my program works with |, example : echo "word" | myProgram.exe?

Answer 1

You need to use Console.Read() and Console.ReadLine() as if you were reading user input. Pipes replace user input transparently. You can't use both easily (although I'm sure it's quite possible...).

Edit:

A simple cat style program:

class Program
{
    static void Main(string[] args)
    {
        string s;
        while ((s = Console.ReadLine()) != null)
        {
            Console.WriteLine(s);
        }

    }
}

And when run, as expected, the output:

C:\...\ConsoleApplication1\bin\Debug>echo "Foo bar baz" | ConsoleApplication1.exe
"Foo bar baz"

C:\...\ConsoleApplication1\bin\Debug>

Answer 2

The following will not suspend the application for input and works when data is or is not piped. A bit of a hack; and due to the error catching, performance could lack when numerous piped calls are made but... easy.

public static void Main(String[] args)
{

    String pipedText = "";
    bool isKeyAvailable;

    try
    {
        isKeyAvailable = System.Console.KeyAvailable;
    }
    catch (InvalidOperationException expected)
    {
        pipedText = System.Console.In.ReadToEnd();
    }

    //do something with pipedText or the args
}

Answer 3

in .NET 4.5 it's

if (Console.IsInputRedirected)
{
    using(stream s = Console.OpenStandardInput())
    {
        ...

Answer 4

This is the way to do it:

static void Main(string[] args)
{
    Console.SetIn(new StreamReader(Console.OpenStandardInput(8192))); // This will allow input >256 chars
    while (Console.In.Peek() != -1)
    {
        string input = Console.In.ReadLine();
        Console.WriteLine("Data read was " + input);
    }
}

This allows two usage methods. Read from standard input:

C:\test>myProgram.exe
hello
Data read was hello

or read from piped input:

C:\test>echo hello | myProgram.exe
Data read was hello

Answer 5

Here is another alternate solution that was put together from the other solutions plus a peek().

Without the Peek() I was experiencing that the app would not return without ctrl-c at the end when doing "type t.txt | prog.exe" where t.txt is a multi-line file. But just "prog.exe" or "echo hi | prog.exe" worked fine.

this code is meant to only process piped input.

static int Main(string[] args)
{
    // if nothing is being piped in, then exit
    if (!IsPipedInput())
        return 0;

    while (Console.In.Peek() != -1)
    {
        string input = Console.In.ReadLine();
        Console.WriteLine(input);
    }

    return 0;
}

private static bool IsPipedInput()
{
    try
    {
        bool isKey = Console.KeyAvailable;
        return false;
    }
    catch
    {
        return true;
    }
}

Answer 6

This will also work for

c:\MyApp.exe < input.txt

I had to use a StringBuilder to manipulate the inputs captured from Stdin:

public static void Main()
{
    List<string> salesLines = new List<string>();
    Console.InputEncoding = Encoding.UTF8;
    using (StreamReader reader = new StreamReader(Console.OpenStandardInput(), Console.InputEncoding))
    {
        string stdin;
        do
        {
            StringBuilder stdinBuilder = new StringBuilder();
            stdin = reader.ReadLine();
            stdinBuilder.Append(stdin);
            var lineIn = stdin;
            if (stdinBuilder.ToString().Trim() != "")
            {
                salesLines.Add(stdinBuilder.ToString().Trim());
            }

        } while (stdin != null);

    }
}

Answer 7

Console.In is a reference to a TextReader wrapped around the standard input stream. When piping large amounts of data to your program, it might be easier to work with that way.

Answer 8

there is a problem with supplied example.

  while ((s = Console.ReadLine()) != null)

will stuck waiting for input if program was launched without piped data. so user has to manually press any key to exit program.