java - java代码设置日期和时间的问题

Question

我正在尝试使用 Java 从远程系统设置 Linux 系统的日期和时间。为了做到这一点，我创建了一个服务器来接受来自远程系统的时间:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class Set_date_n_time {
    public static void main(String[] args) throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        String date_time = new String();
        //@SuppressWarnings("resource")
        ServerSocket s1 = new ServerSocket(7105);
        System.out.println("server started");
        while (true) {
            Socket sckt = s1.accept();
            InputStream input = sckt.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(input));
            date_time = reader.readLine(); 
            String command="sudo date -s "+"\""+date_time+"\"";
            Process p;
            try {
                p = Runtime.getRuntime().exec(command);
                p.waitFor();
                System.out.println ("date set");
                p.destroy();
            } catch (Exception e) {} 
        }
}
}

以及将从中复制时间的远程系统:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Fix_my_Date {

    public static void main(String args[]) throws IOException {
        String addr_list=args[0];
        String[] hostList = readAddressList(addr_list);
        for(int i=0; i<hostList.length;i++) {
        setDate(hostList[i]);
        }
    }


    //@SuppressWarnings("resource")
    private static void setDate(String address) throws IOException {
        {
            Scanner sc = new Scanner(System.in);
            Socket s = null;
            String date =new String();
            String time = new String();
            try {
                s = new Socket(address, 7105);
                System.out.println("connection to "+address+" done");
                Process p, p1;
                try {
                    p = Runtime.getRuntime().exec("date +%Y%m%d");
                    BufferedReader br = new BufferedReader(
                            new InputStreamReader(p.getInputStream()));
                            date = br.readLine();
                            br.close();
                    p.waitFor();
                    p.destroy();
                    p1 = Runtime.getRuntime().exec("date +%H:%M:%S");
                    BufferedReader br1 = new BufferedReader(
                            new InputStreamReader(p1.getInputStream()));
                            time = br1.readLine();
                            br1.close();
                    p1.waitFor();
                    p1.destroy();
                    PrintStream pr = new PrintStream(s.getOutputStream());
                    pr.print(date+" "+time+"");
                    sc.close();
                    s.close();
                } catch (Exception e) {
                    System.out.println("Problem Setting date and time");
                } 


                //s.close();
            } catch (Exception e) {
                System.out.println("Couldn't connect to: "+address+"");
                sc.close();

                //s.close();
            }

        }
        return;
    }


    private static String[] readAddressList(String addr_list) throws IOException {
        FileReader fileReader = new FileReader(addr_list);

        BufferedReader bufferedReader = new BufferedReader(fileReader);
        List<String> lines = new ArrayList<String>();
        String line = null;

        while ((line = bufferedReader.readLine()) != null) 
        {
            lines.add(line);
        }

        bufferedReader.close();

        System.out.println("Loaded the host list");
        return lines.toArray(new String[lines.size()]);

    }

}

但是时间不是由服务器代码设置的。我的错误在哪里？

Answer 1

我、你和许多其他人犯的错误也是(除了这里的其他有用答案之外)你没有阅读标准输出和标准错误，如果你的命令产生任何输出或错误，它就会被阻止，因为没有它可以写入的缓冲区，您可以使用 strace 进行观察。

这可以通过额外的线程来修复，如下所述:https://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html

如果您使用 sudo，如果它不允许在没有终端(requiretty)的情况下使用 sudo，则可能会失败，具体取决于 sudo 设置，请参阅了解更多信息，例如:https://bugzilla.redhat.com/show_bug.cgi?id=1196451