Parameter length too long

Question

I have a java program, and I need to pass to its main method a parameter that has a length of 8k characters. So when I try to execute this program passing that parameter, It just doesn't execute, but no error message is shown. How can I execute correctly that program?

Answer 1

The best solution is to store this 8k parameter inside a file and pass the file name as a parameter. Then inside your main method you should open this file and read the 8k characters.

Answer 2

It is possible that your shell won't allow to exec a program having an argument list above the system limit. Assuming can modify your java program, you should add an option to get the value of the parameter from a file rather than the command-line.

You can also write a wrapper that will invoke your main:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;

public class MyWrapper
{
    public static void main(String[] args) throws Exception
    {
        FileReader reader = new FileReader(args[0]);

        //assuming the data is the first argument
        args[0] = getStringFromReader(reader);

        //invoke real main
        MyClass.main(args);

    }

    public static String getStringFromReader(Reader reader) throws IOException
    {
        final int BUFFER_SIZE = 4096;
        char[] buffer = new char[BUFFER_SIZE];
        Reader bufferedReader = new BufferedReader(reader, BUFFER_SIZE);
        StringBuffer stringBuffer = new StringBuffer();
        int length = 0;
        while ((length = bufferedReader.read(buffer, 0, BUFFER_SIZE)) != -1)
        {
            stringBuffer.append(buffer, 0, length);
        }
        reader.close();

        return stringBuffer.toString();
    }
}

Then, you only need to call java like this:

java MyWrapper my-file-containing-8k-data [other-args...]