Develop Reference

Method to execute Linux command fails

I created the below method to execute a Linux command:
public void executeGetLogs(){
try{
Runtime rt = Runtime.getRuntime();
String [] commands = {helper.getPythonPath(), helper.getLogsMainScript(), helper.getLogsManagementUrl(), helper.getLogsManagementUrlPrefix(), helper.getLogsManagementUsername(), helper.getLogsManagementPassword(), helper.getLogsNet(), helper.getLogsStorageUrl(), helper.getLogStorageUsername(), helper.getLogStoragePassword()};
Process proc = rt.exec(commands);
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(proc.getErrorStream()));
// read the output from the command
logger.debug("Standard output from execution of get_logs:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
logger.debug(s);
}
// read any errors from the attempted command
logger.debug("Standard error from execution of get_logs (if any):\n");
while ((s = stdError.readLine()) != null) {
logger.debug(s);
}
}
catch(IOException e){
logger.debug("Execution exception: " + e);
}
}
The method appears to start working correctly but then fails.
The debug shows the following output:
2017-04-21 12:27:42,391 DEBUG Standard output from execution of get_logs:
2017-04-21 12:27:44,360 DEBUG 411 new files found
2017-04-21 12:27:44,363 DEBUG Downloading files...
2017-04-21 12:27:44,446 DEBUG Standard error from execution of get_logs (if any):
What I would expect to see is
2017-04-21 12:27:44,360 DEBUG 411 new files found
2017-04-21 12:27:44,363 DEBUG Downloading files...
Downloaded 10 of 447
Downloaded 20 of 447
Downloaded 30 of 447
and so on until Downloaded 447 of 447.
I can also see that nothing gets downloaded.
My command runs when I run it in a terminal.
Is it possible something in the Java causes it to exit? One thing is that it can take a few seconds to process each block of 10. Is it possible the
while ((s = stdInput.readLine()) != null) {
logger.debug(s);
}
just sees a null because the stdInput hasn't appeared yet so it exits the loop? If so how can I fix this?

A much better way of executing code in java is ProcessBuilder. Example:
//Create the command.
ProcessBuilder command = new ProcessBuilder(helper.getPythonPath(), helper.getLogsMainScript(), helper.getLogsManagementUrl(), helper.getLogsManagementUrlPrefix(), helper.getLogsManagementUsername(), helper.getLogsManagementPassword(), helper.getLogsNet(), helper.getLogsStorageUrl(), helper.getLogStorageUsername(), helper.getLogStoragePassword());
//Will show console output in java console.
command .inheritIO();
//Launches de command.
Process process= command .start();
Hope it helps.

Got to the bottom of it. I need to wait for the process to end. This can be done with the below code:
proc.waitFor();
My method now looks like this:
public void executeGetLogs(){
try{
Runtime rt = Runtime.getRuntime();
String [] commands = {helper.getPythonPath(), helper.getLogsMainScript(), helper.getLogsManagementUrl(), helper.getLogsManagementUrlPrefix(), helper.getLogsManagementUsername(), helper.getLogsManagementPassword(), helper.getLogsNet(), helper.getLogsStorageUrl(), helper.getLogStorageUsername(), helper.getLogStoragePassword()};
Process proc = rt.exec(commands);
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(proc.getInputStream()));
try{
proc.waitFor();
}
catch(InterruptedException e){
logger.debug("Interrupted Exception : " + e);
}
BufferedReader stdError = new BufferedReader(new
InputStreamReader(proc.getErrorStream()));
// read the output from the command
logger.debug("Standard output from execution of get_logs:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
logger.debug(s);
}
// read any errors from the attempted command
logger.debug("Standard error from execution of get_logs (if any):\n");
while ((s = stdError.readLine()) != null) {
logger.debug(s);
}
}
catch(IOException e){
logger.debug("Execution exception: " + e);
}
}

Opening cmd and waiting user input in cmd and exec commands from java

My problem is, after opening cmd from java code, i want user to be able to input like in c++ ms dos applications. When user writes sth such as "dir" or "cd..", i want to execute these codes by java.
The problem is for every command java re-opens cmd again. Also i cannot execute commands. My cmd start code is below ;
final ArrayList<String> commands = new ArrayList<>();
commands.add("cmd.exe");
commands.add("/C");
commands.add("start");
ProcessBuilder pb = new ProcessBuilder(commands);
Process process = pb.start();

Here's some cleaned up code from How to open the command prompt and insert commands using Java?
public static void main(String[] args) {
try {
String ss = null;
Runtime obj = null;
Process p = Runtime.getRuntime().exec("cmd.exe");
//write a command to the output stream
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));
writer.write("dir");
writer.flush();
//Get the input and stderror
BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(p.getErrorStream()));
System.out.println("Here is the standard output of the command:\n");
while ((ss = stdInput.readLine()) != null) {
System.out.println(ss);
}
System.out.println("Here is the standard error of the command (if any):\n");
while ((ss = stdError.readLine()) != null) {
System.out.println(ss);
}
} catch (IOException e) {
System.out.println("FROM CATCH" + e.toString());
}
}

How can i execute batch file content in java on a server without window popping up

The uploaded Screenshot conatains the start_client.bat file content, viewed in notepad++ editor.
Currently am invoking start_client.bat on local machine it works fine but when the same bat file is invoked on server it pops up a window on server and it needs manual closure after execution. Any way to force bat file execution on server without window poppping up.
private void invokeSeagull(String flag) throws Exception
{
String path="";
if(flag.equals("Start"))
{
path="cmd /c start D:/Seagull/TIB/start_client.bat";
}
if(flag.equals("Stop"))
{
path="cmd /c start D:/Seagull/TIB/stop_client.bat";
}
try {
String line;
Process p = Runtime.getRuntime().exec(path);
p.waitFor();
BufferedReader bri = new BufferedReader
(new InputStreamReader(p.getInputStream()));
BufferedReader bre = new BufferedReader
(new InputStreamReader(p.getErrorStream()));
while ((line = bri.readLine()) != null) {
System.out.println(line);
}
bri.close();
while ((line = bre.readLine()) != null) {
System.out.println(line);
}
bre.close();
p.waitFor();
System.out.println("Done.");
}
catch (Exception err) {
err.printStackTrace();
}
}

This code snippet should run batch file, of course if you use Windows.
Runtime.getRuntime().exec("cmd /c start {pathToFile}");

As pointed out be ssedano the correct way to execute shell commands in Java is the Process-builder:
// Just the name of an executable is enough
final ProcessBuilder pb = new ProcessBuilder( "test.bat" );
pb.redirectError( Redirect.INHERIT );
pb.redirectOutput( Redirect.INHERIT );
System.out.println( String.format( "***** Running Process %s OUTPUT:", pb.command().toString() ) );
final Process process = pb.start();
process.getOutputStream().close();
final int returnCode = process.waitFor();
System.out.println( "***** Process Exited with Returncode: " + returnCode );
You can just redirect STDERR and STDOUT of the bat-file, so you will get all output in the Server-Output console. And you should close STDIN of the bat-file, so it will exit and not get stuck on the pause command at the end!

You could use the new in Java 7 ProcessBuilder
A simple example:
String[] command = {"CMD", "/C", "dir"};
ProcessBuilder probuilder = new ProcessBuilder(command);
// Set up your work directory
probuilder.directory(new File("c:\\stackoverflow"));
Process process = probuilder.start();
// Read output
try (InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);)
{
String line;
System.out.printf("Output of running %s is:\n", Arrays.toString(command));
while ((line = br.readLine()) != null)
{
System.out.println(line);
}
// Wait to get exit value
int exitValue = process.waitFor();
}
catch (Exception e)
{
// Fail
}

This should run in the silent mode :
Runtime.getRuntime().exec(new String[] {"cmd", "/pathto/start_client.bat"});

executing a java program in another java program using Runtime.exec() function

The following code snippet i had given is using exec function and executes hello program (simple "hello world" printing java program). But as soon as i execute the main program, print statement of instream.readline() simply returns NULL. Please try to sort out the problem. Hope the explanation is clear.
CODE:
Process process2=null;
BufferedReader inStream=null;
try
{
process2 = Runtime.getRuntime().exec("java hello");
}
catch(IOException e1)
{
System.err.println("Error on exec method");
e1.printStackTrace();
}
try
{
inStream = new BufferedReader(new InputStreamReader(process2.getInputStream() ));
System.out.println(inStream.readLine());
}
catch(IOException e1)
{
System.err.println("Error on inStream.readLine()");
e1.printStackTrace();
}

First of all your hello.java should be already compiled n the class file should present in the current directory where the program is located.
And for getting errors, you can get error stream from process class's object.
BufferedReader stdError = new BufferedReader(new InputStreamReader(pr.getErrorStream()));
String s="";
while ((s = stdError.readLine()) != null)
System.out.println(s);

Working with Eclipse/java7/windows
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class ProcessDemo {
public static void main(String[] args) throws Exception {
final String dir = System.getProperty("user.dir");
System.out.println("current dir = " + dir);
Runtime run = Runtime.getRuntime();
Process pr=run.exec("javac -d "+ dir +"\\src "+ dir+"\\src\\HelloDemo.java");
pr.waitFor();
BufferedReader stdError = new BufferedReader(new InputStreamReader(pr.getErrorStream()));
BufferedReader buf = new BufferedReader(new InputStreamReader(pr.getInputStream()));
String line = "";
String s;
// read any errors from the attempted command
System.out.println("Here is the standard error of the command (if any):\n");
while ((s = stdError.readLine()) != null)
System.out.println(s);
//read output
while ((line=buf.readLine()) != null)
System.out.println(line);
pr.destroy();
Runtime run1 = Runtime.getRuntime();
Process pr1=run1.exec("java -cp "+dir+"\\src HelloDemo");
BufferedReader stdError1 = new BufferedReader(new InputStreamReader(pr1.getErrorStream()));
BufferedReader buf1 = new BufferedReader(new InputStreamReader(pr1.getInputStream()));
//interpretting file n executing it line by line :D :P
pr1.waitFor();
String temp;
// read any errors from the attempted command
System.out.println("\n\nHere is the standard error of the command (if any):\n");
while ((temp = stdError1.readLine()) != null)
System.out.println(temp);
//read output
System.out.println(buf1.readLine());
while ((temp=buf1.readLine()) != null)
System.out.println(temp);
}
}

Not able to capture output of "who -m" command in JAVA

I want to get the IP address of logged in user of the telnet session
So I have written the following code:
Process p1 = Runtime.getRuntime().exec(new String[] {"/usr/bin/who", "-m"});
p1.waitFor();
BufferedReader reader = new BufferedReader(new InputStreamReader(p1.getInputStream()));
String line = reader.readLine();
System.out.println("line=" + line);
reader.close();
But I am getting the output as "null".
Where as expected output is:
linus pts/1 Dec 10 03:48 (172.21.235.48)

In this case you shouldn't pass the -m option.
This works for me :
Process p1 = Runtime.getRuntime().exec(new String[] {"/usr/bin/who"});

Try to consume the input stream from the process before calling waitFor().

You can create a shell script which will receive parameter (option) from your java program.
Then you can run your shell script from java like this -
ProcessBuilder pb = new ProcessBuilder("/PATH/test.sh","-m");
String line;
Process process=pb.start();
java.io.InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
while ((line = br.readLine()) != null)
{
System.out.println(line);
}
return br;
Now in test.sh, you cab grab the argument and run the command -
/usr/bin/who $1 (needs to check, not sure)
Hope this helps.

Thanks guys for the replies.
From the reply of "dystroy" I understood that -m was creating problem.
I tried --m and it worked :)

Please try this code. It's working for me and returns the same output as who -m UNIX command.
import java.io.*;
public class UserPB
{
public static void main(String[] args)
{
try {
// ProcessBuilder pb = new ProcessBuilder("/u01/app/chdir/user.sh");
ProcessBuilder pb = new ProcessBuilder("who");
Process p;
p = pb.start();
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
System.out.println("Your Host Details--->"+input.readLine());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}