JSch terminal output read is failing if output size is big

Question

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;
    }           
}

What is your larger goal here? Is it just to read the contents of a file? There are simpler ways to do that. — Kenster, Sep 12 '14 at 13:04
yes my goal is to read the contents of remote file. this approach is working but taking lots of time. please suggest me if any efficient way is there to do that. — Rajesh Kumar, Sep 12 '14 at 14:06
More or less a duplicate of http://stackoverflow.com/questions/25657603/how-to-use-java-jsch-library-to-read-remote-file-line-by-line/25694014#25694014 — Kenster, Sep 12 '14 at 15:21

score 1 · Answer 1 · answered Sep 12 '14 at 15:20

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();
}

JSch terminal output read is failing if output size is big

1 Answers1