java - JSch 问题 - 无法检索完整的命令输出

Question

我正在使用 JSch 连接到 SSH 并执行命令。其中一个命令给出了一个很大的输出。在终端中，如果执行命令，则必须按 Enter 键才能查看整个输出。使用 JSch 我无法检索整个输出。

当我使用交互式终端登录时，命令输出在填满屏幕后停止并等待 Enter。

代码取自 How to get jsch shell command output in String :

public class SshConnectionManager {

    private static Session session;
    private static ChannelShell channel;
    private static String username = "";
    private static String password = "";
    private static String hostname = "";


    private static Session getSession(){
        if(session == null || !session.isConnected()){
            session = connect(hostname,username,password);
        }
        return session;
    }

    private static Channel getChannel(){
        if(channel == null || !channel.isConnected()){
            try{
                channel = (ChannelShell)getSession().openChannel("shell");
                channel.connect();

            }catch(Exception e){
                System.out.println("Error while opening channel: "+ e);
            }
        }
        return channel;
    }

    private static Session connect(String hostname, String username, String password){

        JSch jSch = new JSch();

        try {

            session = jSch.getSession(username, hostname, 22);
            Properties config = new Properties(); 
            config.put("StrictHostKeyChecking", "no");
            session.setConfig(config);
            session.setPassword(password);

            System.out.println("Connecting SSH to " + hostname + " - Please wait for few seconds... ");
            session.connect();
            System.out.println("Connected!");
        }catch(Exception e){
            System.out.println("An error occurred while connecting to "+hostname+": "+e);
        }

        return session;

    }

    private static void executeCommands(List<String> commands){

        try{
            Channel channel=getChannel();

            System.out.println("Sending commands...");
            sendCommands(channel, commands);

            readChannelOutput(channel);
            System.out.println("Finished sending commands!");

        }catch(Exception e){
            System.out.println("An error ocurred during executeCommands: "+e);
        }
    }

    private static void sendCommands(Channel channel, List<String> commands){

        try{
            PrintStream out = new PrintStream(channel.getOutputStream());

            out.println("#!/bin/bash");
            for(String command : commands){
                out.println(command);
            }
            out.println("exit");

            out.flush();
        }catch(Exception e){
            System.out.println("Error while sending commands: "+ e);
        }

    }

    private static void readChannelOutput(Channel channel){

        byte[] buffer = new byte[1024];

        try{
            InputStream in = channel.getInputStream();
            String line = "";
            while (true){
                while (in.available() > 0) {
                    int i = in.read(buffer, 0, 1024);
                    if (i < 0) {
                        break;
                    }
                    line = new String(buffer, 0, i);
                    System.out.println(line);
                }

                if(line.contains("logout")){
                    break;
                }

                if (channel.isClosed()){
                    break;
                }
                try {
                    Thread.sleep(1000);
                } catch (Exception ee){}
            }
        }catch(Exception e){
            System.out.println("Error while reading channel output: "+ e);
        }

    }

    public static void close(){
        channel.disconnect();
        session.disconnect();
        System.out.println("Disconnected channel and session");
    }


    public static void main(String[] args){
        List<String> commands = new ArrayList<String>();
        commands.add("ls -l");

        executeCommands(commands);
        close();
    }
}

Answer 1

您通常不应使用“shell” channel 来自动执行命令。

“shell” channel 旨在实现交互式 shell session 。

因此它请求 PTY(伪终端)，它具有对人类友好但对机器不友好的副作用，会破坏您的代码。

改用“exec” channel 。

参见Execute a list of commands from an ArrayList using JSch exec in Java

<小时/>

如果您出于某种原因需要或想要使用“shell” channel (但不这样做，无论如何它都会咬您)，请确保在 之前调用 .setPty(false) .connect:

channel = (ChannelShell)getSession().openChannel("shell");
channel.setPty(false);
channel.connect();

<小时/>

旁注:

• “#!/bin/bash”纯粹是无稽之谈。 shell 会忽略所有以 # 开头的命令(它是注释)。寄出去也没啥意义
• 请勿使用StrictHostKeyChecking=no。请参阅JSch SFTP security with session.setConfig(“StrictHostKeyChecking”, “no”); .