Send an SFTP command by using runtime.exec

Question

I would like to download a file from an sftp server by using the class Runtime of Java. I can't use a library like Jsch or SSHJ because i need to use the -B option to increase the buffer size. I've tried with this code so far:

public void download(String source, String destination,String port, String user, String host ){
    Runtime runtime = Runtime.getRuntime();
    String cmd = "sftp -oPort=" + port + " -B 150000 "+ user + "@" + host + ":" + source + " " + destination;

    String[] args = { "/bin/sh", "-c", cmd };
    try {
        long startTime = System.currentTimeMillis();
        log.info("cmd: "+ cmd);
        final Process process = runtime.exec(args);
        process.waitFor();
        long stopTime = System.currentTimeMillis();
        long elapsedTime = stopTime - startTime;
        System.out.println("Time: "+elapsedTime);

        BufferedReader bre = new BufferedReader(new InputStreamReader(process.getErrorStream()));
        StringBuffer sbe = new StringBuffer();
        String lineError;
        while ((lineError = bre.readLine()) != null) {   
          sbe.append(lineError).append("\n");
        }   
        String answerError = sbe.toString();
        if(answerError.length()>0)log.error("Error:"+answerError);
    } catch (IOException e) {
        e.printStackTrace();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

I get the error message : Connecting to xxxxxxx... with the name of the host instead of the "xxxxxx"

I've tried the command directly in putty and it works great but when i use it in java it doesn't work at all. I've also tried an scp command with runtime.exec() for downloading instead of an sftp and that work.

Does someone have a clue why it's not working? I can't find an exemple with this method. Or does someone know a library for sftp transfer that allows to set the -B option? i've maybe missed a method in Jsch and Sshj.

Thanks in advance

Not sure this will help, but have you tried getting the process output stream and seeing if there is any more information there? — Mark Wagoner, Jul 31 '14 at 10:52
[Here](http://www.jcraft.com/jsch/examples/Sftp.java.html) is a library you can use. What means "when i use it in java it doesn't work at all"? — Jens, Aug 11 '14 at 19:21

Andrew · Answer 1 · 2014-08-11T19:18:53.243

I do this using psftp on windows. I expect your results using sftp on *nix should be the same.

 static java.io.File downloadFileViaSftp(String file) {
    String string = null;

    try {
        String c = "psftp -l user -P 22 -v -pw password hostname";
        Process p = Runtime.getRuntime().exec(c);

        OutputStream out = p.getOutputStream();

        Writer out2 = new BufferedWriter(new OutputStreamWriter(out));

        out2.write("get " + file + "\n");
        out2.flush();
        out2.write("close\n");
        out2.flush();
        out2.write("quit\n");
        out2.flush();
        out2.close();

        InputStream in = p.getInputStream();
        InputStream err = p.getErrorStream();

        BufferedReader bufferedreader1 = new BufferedReader(new InputStreamReader(in), 999999);
        BufferedReader bufferedreader2 = new BufferedReader(new InputStreamReader(err), 999999);

        while ((string = bufferedreader2.readLine()) != null) {
            System.out.println("2=" + string);
            System.out.flush();
        }
        bufferedreader2.close();

        while ((string = bufferedreader1.readLine()) != null) {
            System.out.println("1=" + string);
            System.out.flush();
        }
        bufferedreader1.close();

        int x = p.waitFor();
        p.destroy();

    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }

    return new java.io.File(file);

}

Send an SFTP command by using runtime.exec

1 Answers1