Develop Reference

Java runtime getInputStream ignores majority of terminal command output

I'm writing a Java program to capture the output of a terminal command. Under "normal" conditions, i.e. where I execute the command directly into the terminal myself, I can see the following result:
However, the output rendered by my Java program only captures a small subset of that, see here:
This is the codebase I'm speaking of:
import java.io.*;
class evmTest {
public static void main(String[] args) {
String evmResult = "";
String evmCommand = "evm --debug --code 7f00000000000000000000000000000000000000000000000000000000000000027f00000000000000000000000000000000000000000000000000000000000000027f00000000000000000000000000000000000000000000000000000000000000020101 run";
try {
Runtime r = Runtime.getRuntime();
Process p = r.exec(evmCommand);
BufferedReader in = new BufferedReader(new
InputStreamReader(p.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
System.out.println(inputLine);
evmResult += inputLine;
}
in.close();
} catch (IOException e) {
System.out.println(e);
}
}
}
Thus far I've not been able to determine why that code is only able to emit the paltry 0x. I've posted this question in the hopes that someone might be able to help me track down the cause of this error.

do it like this:
import java.io.*;
class evmTest {
public static void main(String[] args) {
String evmResult = "";
String evmCommand = "evm --debug --code 7f00000000000000000000000000000000000000000000000000000000000000027f00000000000000000000000000000000000000000000000000000000000000027f00000000000000000000000000000000000000000000000000000000000000020101 run";
try {
Runtime rt = Runtime.getRuntime();
String command = "evm --debug --code 7f00000000000000000000000000000000000000000000000000000000000000027f00000000000000000000000000000000000000000000000000000000000000027f00000000000000000000000000000000000000000000000000000000000000020101 run";
Process proc = rt.exec(command);
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(proc.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(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);
}
} catch (IOException e) {
System.out.println(e);
}
}
}

How to start Rserve automatically from Java?

I am writing a Java application in IntelliJ IDE. The application used Rserve package to connect to R and perform some functions. When I want to run my code for the first time, I have to launch R in the command line and start the Rserve as a daemon, which looks something like this:
R
library(Rserve)
Rserve()
After doing this, I can easily access all the function in R without any errors. However, since this Java code would be bundled as an executable file, so is there a way that Rserve() is invoked automatically as soon as the code is run so that I have to skip this manual step of starting Rserve using the command line?

Here is the code for the Class I wrote to get Rserve working from Java
public class InvokeRserve {
public static void invoke() {
String s;
try {
// run the Unix ""R CMD RServe --vanilla"" command
// using the Runtime exec method:
Process p = Runtime.getRuntime().exec("R CMD RServe --vanilla");
BufferedReader stdInput = new BufferedReader(new
InputStreamReader(p.getInputStream()));
BufferedReader stdError = new BufferedReader(new
InputStreamReader(p.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
while ((s = stdInput.readLine()) != null) {
System.out.println(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);
}
// System.exit(0);
}
catch (IOException e) {
System.out.println("exception happened - here's what I know: ");
e.printStackTrace();
System.exit(-1);
}
}
}

I know this question has been asked a long back . I think You have the answer. But the below answer may help others. That's why I am posting my answer.
answer:- Instead of going again and again to the R console to start Rserve. One thing you can do is you can write a java program to start Rserve.
Below code you can use in a java program to start Rserve.
https://www.sitepoint.com/community/t/call-linux-command-from-java-application/3751. This is the link where you will get the code to run a linux command from java.I have changed the command only and posting below.
package javaapplication13;
import java.io.*;
public class linux_java {
public static void main(String[] args) {
try {
String command ="R CMD Rserve";
BufferedWriter out = new BufferedWriter(new FileWriter(
new File(
"/home/jayshree/Desktop/testqavhourly.tab"), true));
final Process process = Runtime.getRuntime().exec(command);
BufferedReader buf = new BufferedReader(new InputStreamReader(
process.getInputStream()));
String line;
while ((line = buf.readLine()) != null) {
out.write(line);
out.newLine();
}
buf.close();
out.close();
int returnCode = process.waitFor();
System.out.println("Return code = " + returnCode);
} catch (Exception e) {
e.printStackTrace();
}
}
}

Runtime.getRuntime failed to get output same time but later

I'm currently making firefox addon development GUI tool using Java. However I am stuck when trying to get output of a .bat file.
When I run .bat file using java I can see the output, but there are 3 commands written in the bat file. When first command executes I can get the output simultaneously. But when it execute second command output not coming. And when .bat file exist I get all the output which didn't come simultaneously.
I'm getting output immediately when it execute:
call "C:\mozilla-build\addon-sdk-1.16\bin\activate.bat
But I'm not getting output simultaneously for following command:
call cfx run
But I know it's executing because firefox window pops up. I get all the output suddenly when I execute proc.destroy();
This is my bat file:
#echo off
call %1
cd C:\Users\Madhawa.se\Desktop\workingfox\beauty
call cfx run
pause
This is my Java code:
Thread t = new Thread(new Runnable() {
#Override
public void run() {
try {
Runtime rt = Runtime.getRuntime();
String[] commands = {"C:\\Users\\Madhawa.se\\Desktop\\workingfox\\runner\\foxrun.bat", "C:\\mozilla-build\\addon-sdk-1.16\\bin\\activate.bat"};
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
String s = null;
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
// read any errors from the attempted command
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
proc.waitFor();
System.out.println("success");
} catch (Exception ex) {
ex.printStackTrace();
}
}
});
t.start();
How to get output immediately and why it acts differently for this command?

i was able to fix it using process builder instead of runtime.exec .and inheriteIo doesn't work .it blocks the realtime output
Thread t = new Thread(new Runnable() {
private String s;
#Override
public void run() {
try {
Component selectedComponent = jTabbedPane2.getSelectedComponent();
if (selectedComponent instanceof MyTextArea) {
String response = "";
System.out.println("yes");
MyTextArea temptextarea = (MyTextArea) selectedComponent;
String xpiPath = new File(temptextarea.getNameX()).getParentFile().getPath();
String[] commands = {"C:\\Users\\Madhawa.se\\Desktop\\workingfox\\runner\\foxrun.bat", "C:\\mozilla-build\\addon-sdk-1.16\\bin\\activate.bat
ProcessBuilder process = new ProcessBuilder(commands);
process.redirectErrorStream(true);
Process shell = process.start();
//shell.waitFor();
BufferedReader stdInput = new BufferedReader(new InputStreamReader(shell.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(shell.getErrorStream()));
// read the output from the command
System.out.println("Here is the standard output of the command:\n");
while ((s = stdInput.readLine()) != null) {
System.out.println("s:" + 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("w:" + s);
}
}
} catch (Exception ex) {
ex.printStackTrace();
}

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);
}
}

How to Execute Windows Commands Using Java - Change Network Settings

In Java, I want to be able to execute a Windows command.
The command in question is netsh. This will enable me to set/reset my IP address.
Note that I do not want to execute a batch file.
Instead of using a batch file, I want to execute such commands directly. Is this possible?
Here is my implemented Solution for Future Reference:
public class JavaRunCommand {
private static final String CMD =
"netsh int ip set address name = \"Local Area Connection\" source = static addr = 192.168.222.3 mask = 255.255.255.0";
public static void main(String args[]) {
try {
// Run "netsh" Windows command
Process process = Runtime.getRuntime().exec(CMD);
// Get input streams
BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));
// Read command standard output
String s;
System.out.println("Standard output: ");
while ((s = stdInput.readLine()) != null) {
System.out.println(s);
}
// Read command errors
System.out.println("Standard error: ");
while ((s = stdError.readLine()) != null) {
System.out.println(s);
}
} catch (Exception e) {
e.printStackTrace(System.err);
}
}
}

Runtime.getRuntime().exec("netsh");
See Runtime Javadoc.
EDIT: A later answer by leet suggests that this process is now deprecated. However, as per the comment by DJViking, this appears not to be the case: Java 8 documentation. The method is not deprecated.

Use ProcessBuilder
ProcessBuilder pb=new ProcessBuilder(command);
pb.redirectErrorStream(true);
Process process=pb.start();
BufferedReader inStreamReader = new BufferedReader(
new InputStreamReader(process.getInputStream()));
while(inStreamReader.readLine() != null){
//do something with commandline output.
}

You can run the command with Runtime.getRuntime().exec("<command>") (eg. Runtime.getRuntime().exec("tree")). But, this will only run executables found in path, not commands like echo, del, ... But only stuff like tree.com, netstat.com, ... To run regular commands, you will have to put cmd /c before the command (eg Runtime.getRuntime().exec("cmd /c echo echo"))

public static void main(String[] args) {
String command="netstat";
try {
Process process = Runtime.getRuntime().exec(command);
System.out.println("the output stream is "+process.getOutputStream());
BufferedReader reader=new BufferedReader( new InputStreamReader(process.getInputStream()));
String s;
while ((s = reader.readLine()) != null){
System.out.println("The inout stream is " + s);
}
} catch (IOException e) {
e.printStackTrace();
}
}
This works.

Runtime#exec().