Provided your command is properly formatted, I have found Jsch will close the channel once the command is complete as long as you read the output in a timely manner. In the JCraft example, channel.isClosed() is the only thing they check for the command being complete. They read the output in the same thread that waits for the channel to close. A fancier way to do this is to create a separate thread to read the output. Example follows:
Jsch Code:
Channel channel = null;
int exitStatus = 0;
List<String> lines = new ArrayList<String>();
try {
channel = session.openChannel("exec");
((ChannelExec) channel).setCommand(command);
// Read output in separate thread
Thread stdoutReader = new InputStreamHandler(channel.getInputStream(), "STDOUT", lines);
// Run the command
((ChannelExec)channel).setCommand(command);
channel.connect();
// Start thread that reads output
stdoutReader.start();
// Poll for closed status
boolean channelClosed = channel.isClosed();
exitStatus = channel.getExitStatus();
boolean stdOutReaderAlive = stdoutReader.isAlive();
int loopCounter = 0;
while (!channelClosed) {
if (loopCounter % 60 == 0) {
log.info("SSH command '" + command + "' still in while loop checking for after " + (loopCounter/60) + " mins.");
}
loopCounter++;
Thread.sleep(1000);
channelClosed = channel.isClosed();
exitStatus = channel.getExitStatus();
stdOutReaderAlive = stdoutReader.isAlive();
}
log.info("SSH command '" + command + "' exited while loop with values: channelClosed=" + channelClosed + ", exitStatus=" + exitStatus + ", stdOutReaderAlive=" + stdOutReaderAlive);
// finish reading output
stdoutReader.join();
exitStatus = channel.getExitStatus();
log.info("SSH command '" + command + "' final exitStatus=" + exitStatus);
for (String line : lines) {
log.info("SSH output: " + line);
}
} catch (Exception e) {
throw new RuntimeException("Error occured processing SSH request. See nested exception for details.", e);
} finally {
// Always try to close the channel and session.
try {
channel.disconnect();
} catch(Exception e) {
this.log.error("Error - disconnecting channel", e);
}
try {
session.disconnect();
} catch(Exception e) {
this.log.error("Error - disconnecting session", e);
}
}
InputStreamHandler:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.InterruptedIOException;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
/**
* A lot of debate on how to stop a thread... going with the method given here: http://www.javaspecialists.eu/archive/Issue056.html
*/
public class InputStreamHandler extends Thread {
protected Log logger = LogFactory.getLog(getClass());
private InputStream is = null;
private String type = null;
private StringBuilder buffer;
private List<String> lines;
public InputStreamHandler(InputStream is, String type) {
this.is = is;
this.type = type;
}
public InputStreamHandler(InputStream is, String type, StringBuilder buffer) {
this(is, type);
this.buffer = buffer;
}
public InputStreamHandler(InputStream is, String type, List<String> lines) {
this(is, type);
this.lines = lines;
}
public void run() {
try {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
if (buffer != null) {
String line = null;
while ((line = br.readLine()) != null) {
buffer.append(line + "\n");
}
} else if (lines != null) {
String line = null;
while ((line = br.readLine()) != null) {
lines.add(line);
}
} else {
// just consume output
while (br.readLine() != null)
;
}
} catch (InterruptedIOException ioe) {
// when exception is thrown the interrupt flag is set to false... this will set it back to true
Thread.currentThread().interrupt();
} catch (IOException ioe) {
if (!isInterrupted()) {
throw new RuntimeException("Caught IQException for "
+ this.type + " " + this.getClass().getName() + ".",
ioe);
}
} finally {
closeInputStream();
}
}
@Override
public void interrupt() {
super.interrupt();
closeInputStream();
logger.info(this.type + " " + this.getClass().getName()
+ " thread was interrupted.");
}
private void closeInputStream() {
try {
is.close();
} catch (Exception e) {
}
}
}
