CODEWITHSUNDEEP
javajsch
Rajesh Kumar
Rajesh Kumar

Reputation: 349

JSch terminal output read is failing if output size is big

I am trying to execute a cat command on remote machine using JSch and reading the output.I gets output in case file is small. but if file size is large, I am not getting output and execution of command gets hanged.

please suggest me how to over come this problem

part of the code:

JSch jSch = new JSch();
Properties config = new Properties();
config.put("StrictHostKeyChecking", "no");
command = "cat test1.properties"
Session jsession = jSch.getSession(this.username, this.host, 22);
jsession.setPassword(this.password);
jsession.setConfig("StrictHostKeyChecking", "no");
jsession.connect();
Channel channel = jsession.openChannel("shell");
OutputStream ops = channel.getOutputStream();
PrintStream ps = new PrintStream(ops, true);
channel.connect();
boolean isPasswordEntered=false;
boolean isYesOrNoEntered=false;
StringBuilder sb = new StringBuilder();
byte[] tmp = new byte[1024];

int timeout = 60*1000;
long end = System.currentTimeMillis() + timeout; // 60 seconds * 1000 ms/sec , max 5 minutes 
InputStream in = channel.getInputStream();

while (true){
    if (System.currentTimeMillis()>end){
        break;
    }
    while (in.available() > 0) {
        end = System.currentTimeMillis()+timeout;
        int i = in.read(tmp, 0, 1024);
        if (i < 0) {
            break;
        }
        sb.append(new String(tmp, 0, i));
        if (!isYesOrNoEntered && sb.indexOf("yes")!=-1){ 
            isYesOrNoEntered = true;
            print.println("yes");
            Thread.sleep(500);
        }
        if (!isPasswordEntered && sb.toString().toLowerCase().indexOf("password")!=-1){     
            isPasswordEntered = true;
            print.println(nsmailPassword);
            LOG.debug("entering the nsmail password");
            Thread.sleep(500);
        }
    }
    if (channel.isClosed()) {
        if (in.available() > 0) {
            continue;
        }
        break;
    }           
}

Upvotes: 1

Views: 1104

Answers (1)

Kenster
Kenster

Reputation: 25439

To read a remote file through ssh, you're better off using sftp than pure ssh. Jsch has built-in support for sftp. Once you've opened a session, do this to open an sftp channel:

ChannelSftp sftp = (ChannelSftp) session.openChannel("sftp");

Once you've opened an sftp channel, there are methods to read a remote file which let you access the file's content as an InputStream:

InputStream stream = sftp.get("/some/file");

You can convert that to a Reader if you need to read line-by-line:

InputStream stream = sftp.get("/some/file");
try {
    BufferedReader br = new BufferedReader(new InputStreamReader(stream));
    // read from br
} finally {
    stream.close();
}

Upvotes: 1

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