Jsch - One Session Multiple Channels
Solution 1
Hey I have exactly the same problem with jsch and Ubuntu. (How) did you solve it? Making a new session for every execute eats too much time? At the moment I catch the jsch exception and search for "session isn't down" then I reconnect the session and execute command again. That works but is not a good solution.
Edit: I was on the wrong way I solved my problem for now by using
channel = session.openChannel("shell");
instead of "exec".
Solution 2
Here is a complete working Java class based on @krishna's answer:
/**
* Run several ssh commands in a single JSch session
*/
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import java.io.*;
class SshMultiCommands
{
public static void main(String[] args) throws Exception
{
JSch jsch = new JSch();
String user = "user"; //CHANGE ME
String host = "192.168.222.157"; //CHANGE ME
String passwd = "password"; //CHANGE ME
int port = 22;
Session session = jsch.getSession(user, host, port);
session.setPassword(passwd);
session.setConfig("StrictHostKeyChecking", "no");
session.connect();
Channel channel = session.openChannel("shell");
OutputStream ops = channel.getOutputStream();
PrintStream ps = new PrintStream(ops, true);
channel.connect();
InputStream input = channel.getInputStream();
//commands
ps.println("ls -lag");
ps.println("cd /etc");
ps.println("ls");
ps.println("exit");
ps.close();
printResult(input, channel);
channel.disconnect();
session.disconnect();
}
/**
* @param input
* @param channel
*/
private static void printResult(InputStream input,
Channel channel) throws Exception
{
int SIZE = 1024;
byte[] tmp = new byte[SIZE];
while (true)
{
while (input.available() > 0)
{
int i = input.read(tmp, 0, SIZE);
if(i < 0)
break;
System.out.print(new String(tmp, 0, i));
}
if(channel.isClosed())
{
System.out.println("exit-status: " + channel.getExitStatus());
break;
}
try
{
Thread.sleep(300);
}
catch (Exception ee)
{
}
}
}
}
Solution 3
you can use shell to execute multiple commands. following is the code to execute commands via shell.
Channel channel=session.openChannel("shell");
OutputStream ops = channel.getOutputStream();
PrintStream ps = new PrintStream(ops, true);
channel.connect();
ps.println("mkdir folder");
ps.println("dir");
//give commands to be executed inside println.and can have any no of commands sent.
ps.close();
InputStream in=channel.getInputStream();
byte[] bt=new byte[1024];
while(true) {
while(in.available()>0) {
int i=in.read(bt, 0, 1024);
if(i<0)
break;
String str=new String(bt, 0, i);
//displays the output of the command executed.
System.out.print(str);
}
if(channel.isClosed())
break;
Thread.sleep(1000);
channel.disconnect();
session.disconnect();
}
Solution 4
If you want to use exec. you can run multiple commands by putting a semi colon (;) within commands
like:
pwd;ls- -l;
cd foldername
((ChannelExec) channel).setCommand("pwd;ls -l; cd foldername");
Solution 5
I used exactly same code and had problem some of the times reading output of the script i executed through ssh. Sometimes the program was missing the all content, and sometime only a part of the content. I resolved my problem by changing the if(channel.isclosed) in the nested loop. Here is the new code
while (true) {
while (in.available() > 0) {
int i = in.read(tmp, 0, 1024);
if (i < 0)
break;
System.out.print(new String(tmp, 0, i));
}
if (channel.isClosed()) {
if(in.available() > 0) {
int i = in.read(tmp, 0, 1024);
System.out.print(new String(tmp, 0, i));
}
System.out.println("exit-status: " + channel.getExitStatus());
break;
}
try {
Thread.sleep(1000);
} catch (Exception ee) {
}
Nick Russler
Updated on February 01, 2020Comments
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Nick Russler about 4 years
I managed to execute a single command through ssh with Jsch but when i try to execute a second command it fails
For debugging i brought this problem down to this lines:
import java.io.IOException; import java.io.InputStream; import com.jcraft.jsch.Channel; import com.jcraft.jsch.ChannelExec; import com.jcraft.jsch.JSch; import com.jcraft.jsch.JSchException; import com.jcraft.jsch.Session; public class Exec { public static void test(Session session) throws Exception { Channel channel = session.openChannel("exec"); ((ChannelExec) channel).setCommand("pwd"); channel.setInputStream(null); ((ChannelExec) channel).setErrStream(System.err); InputStream in = channel.getInputStream(); channel.connect(); byte[] tmp = new byte[1024]; while (true) { while (in.available() > 0) { int i = in.read(tmp, 0, 1024); if (i < 0) break; System.out.print(new String(tmp, 0, i)); } if (channel.isClosed()) { System.out.println("exit-status: " + channel.getExitStatus()); break; } try { Thread.sleep(1000); } catch (Exception ee) { } } channel.disconnect(); } public static void main(String[] arg) { try { JSch jsch = new JSch(); Session session = jsch.getSession("nck", "127.0.0.1", 22); session.setPassword("asd"); session.setConfig("StrictHostKeyChecking", "no"); session.connect(); test(session); // This one succeeds with exit-status: 0 test(session); // This one fails with exit-status: 255 session.disconnect(); } catch (Exception e) { // } } }
This is mostly the official Exec example but this gives me this output:
/home/nck exit-status: 0 exit-status: 255
The first command is executed succesfully the second doesnt.
Any Ideas ?
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svarog about 7 yearsI tried all solutions and this is the best solution