java input.readLine hangs after starting a powershell script

java input.readLine hangs after starting a powershell script - java

We are trying to call a Powershell script via Java but it hangs when we try to read the output of that script. It hangs on "input.readLine()"
Here is a code we have tried:
String command = "cmd /c powershell C:\\_checkouts\\TestPowerShell\\passwordExpirationTime.ps1";
Process p = Runtime.getRuntime().exec(command);
new InputStreamReader(p.getInputStream());
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
StringBuilder stringBuilder = new StringBuilder();;
for (String line = input.readLine(); line != null; line = input.readLine()) {
stringBuilder.append(line);
}
input.close();
String msg = stringBuilder.toString();
System.out.println("msg: " + msg);
We tried looking at this solution Java program hangs when trying to invoke powershell script
but none of those suggestions worked for us.
We also tried it without cmd /c and with cmd /k. We really want this as a generic class where any script could be called. i.e. BAT, BASH, SH, Powershell, etc.
Any ideas?
Thanks to the answer below here is the code that worked:
try{
final ProcessBuilder pb = new ProcessBuilder("powershell","C:\\psFile.ps1");
pb.redirectInput(Redirect.from(new File("NUL")));
final Process p = pb.start();
final int retcode = p.waitFor();
InputStream is = p.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
br.close();
}catch (Exception e){
e.printStackTrace();
}
Here's some additional information. Our powershell was returning an error because it was restricted. That is why we needed all the Redirect to NUL. Once we fixed that and it wasn't returning an error we were able to simplify our code to this:
try{
final ProcessBuilder pb;
pb = new ProcessBuilder(args);
final Process p = pb.start();
InputStream is = p.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
br.close();
}catch (Exception e){
e.printStackTrace();
}

Use a ProcessBuilder. Any process implying a modicum of I/O should outright refuse to run via Runtime.exec(), alas, it cannot detect that. And Oracle hasn't flagged it as #Deprecated which is a pity.
Anyway:
final File logFile = new File("/path/to/logfile");
final ProcessBuilder pb = new ProcessBuilder("powershell", "/path/to/the/ps1");
pb.redirectOutput(Redirect.to(logFile));
pb.redirectErrorStream(true);
final Process p = pb.start();
final int retcode = p.waitFor();
// deal with retcode
// read result from the log file

Related

How to execute commands inside a shell using Process object in Java

I executed a shell using:
Process process = Runtime.getRuntime().exec("docker exec rabbitmq bash");
But now, I want to execute another command inside the opened shell:
Writer w = new OutputStreamWriter(process.getOutputStream(), "UTF-8");
w.write("rabbitmqctl list_queues\n");
w.flush();
But I can't get the output of rabbitmqctl list_queues
BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
I don't get any errors, if I use a malformed command, it will issue an error message:
BufferedReader error = new BufferedReader(new InputStreamReader(process.getErrorStream()));
String errorString = error.readLine();
System.out.println("\nError : " + errorString);
int exitCode = process.waitFor();

The problem was the lack of use of -i parameter:
Process process = Runtime.getRuntime().exec("docker exec -i rabbitmq bash");
But, using only Process class I had had problems, the interpreter didn't understand the end of output and the loop didn't stop:
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
But using ProcessBuilder it worked:
#Test
void test_process_builder() throws IOException {
ProcessBuilder builder = new ProcessBuilder("docker","exec","-i","rabbitmq3","bash");
Process process = builder.start();
OutputStream stdin = process.getOutputStream(); // <- Eh?
InputStream stdout = process.getInputStream();
InputStream stderr = process.getErrorStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(stdout));
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(stdin));
BufferedReader error = new BufferedReader(new InputStreamReader(stderr));
writer.write("rabbitmqctl list_queues \n");
writer.flush();
writer.close();
Scanner err = new Scanner(stderr);
while (err.hasNextLine()) {
System.out.println(err.nextLine());
}
Scanner scanner = new Scanner(stdout);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}
}

Run system commands in java

I am a little confused about why I can't run the following command ls -l
If I run ls or pwd it works fine.
Am I missing something?
ProcessBuilder pb = new ProcessBuilder("ls -l");
pb.redirectErrorStream(true);
Process process = pb.start();
InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
while ( (line = br.readLine()) != null) {
System.out.println(line);
}
br.close();
One more question: How can I run multiple system commands concurrently? Using while loop or for loops will run the command one by one. Any advice?
Thanks in advance.

Change:
new ProcessBuilder("ls -l");
To:
new ProcessBuilder("ls", "-l");

String[] st = {"ls", "bin"};
ProcessBuilder pb = new ProcessBuilder(st);
pb.redirectErrorStream(true);
Process process = pb.start();
InputStream is = process.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
while ( (line = br.readLine()) != null) {
System.out.println(line);
}
br.close();

Using while loop or for loops will run the command one by one.
Only when you are doing the whole start-then-read-stdout business for each one of them, one-by-one. The processes are indeed run in parallel, it's just the reading part that's stopping you from running them concurrently. All you need to do is breaking the start and read into two parts:
Stream.of(Arrays.asList("ls", "-l"),
Arrays.asList("python", "-h"),
Arrays.asList("df"))
.map(cmd->{
// Create a process for each command, but don't read the output
try {
return new AbstractMap.SimpleImmutableEntry<>(cmd,
new ProcessBuilder(cmd)
.redirectErrorStream(true)
.start().getInputStream());
} catch (IOException e) {
e.printStackTrace();
return null;
}
})
.filter(p->p!=null)
.parallel()
.forEach(in->{
// Read and print STDOUT for each process.
try (BufferedReader reader = new BufferedReader(new InputStreamReader(in.getValue()))){
String line;
while ((line = reader.readLine()) != null) {
System.out.printf("%20s: %s\n", in.getKey(), line);
}
} catch (IOException e) {
e.printStackTrace();
}
});
The parallel() call is making the output really hard to read, it's there only to demonstrate that the processes are really running concurrently.

Java: Pass values to the jar using OutputStreamWriter

I'm trying to execute myfile.jar using another java program which as follows. When the myfile.jar is executed standalone in console, it will as two questions:
Start the load process (y/n)?
Start the patch process (y/n)?
I will pass y to 1st and n to 2nd question. The same thing I'm trying to do using the following java program and it successfully passes answer to the 1st question, but waiting at the 2nd question.
ProcessBuilder pb = new ProcessBuilder("java", "-jar", "myfile.jar", "arg1");
pb.redirectErrorStream(true);
Process p = pb.start();
InputStream in = p.getInputStream();
InputStreamReader ins = new InputStreamReader(in);
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(p.getOutputStream());
BufferedReader br = new BufferedReader(ins);
String line = null;
out.write("y\n");
out.write("n\n");
out.flush();
while ((line = br.readLine()) != null) {
System.out.println(line);
}
out.close();
p.waitFor();
p.destroy();
Note: The myfile.jar uses Scanner to take the input from the user.

I guess I found the solution to my question. For future reference, the following is the final program that I've used to solve my problem:
ProcessBuilder pb = new ProcessBuilder("java", "-jar", "myfile.jar", "arg1");
pb.redirectErrorStream(true);
Process p = pb.start();
InputStream in = p.getInputStream();
InputStreamReader ins = new InputStreamReader(in);
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(p.getOutputStream());
BufferedReader br = new BufferedReader(ins);
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
if (line.contains("Start the load process (y/n)?")) {
out.write("y");
out.newLine();
out.flush();
}
if (line.contains("Start the patch process (y/n)?")) {
out.write("n");
out.newLine();
out.flush();
}
}
out.close();
p.waitFor();
p.destroy();

Java run Windows command line command returning a value

I would like to run a windows command line command from java and return the result into java. Is this possible?
for example, I would like to do the following
Object returnValue = runOnCommandLine("wmic cpu get LoadPercentage");
//In this case, returnValue is the cpu load percent as a String
Edit: I was able to get this working
InputStream inputStream = new ProcessBuilder("wmic", "cpu", "get", "status").start().getInputStream();
StringWriter writer = new StringWriter();
IOUtils.copy(inputStream, writer);
String theString = writer.toString();
System.out.println("My string: " + theString);

Data you need is commandOutput.
String cmd = "wmic cpu get LoadPercentage";
ProcessBuilder pb = new ProcessBuilder(cmd);
pb.redirectErrorStream(true);
Process p = pb.start();
BufferedReader stdin = new BufferedReader(
new InputStreamReader(p.getInputStream()));
StringBuilder commandOutput = new StringBuilder();
String line;
while ((line = stdin.readLine()) != null) {
commandOutput.append(line);
}
int exitValue = -1;
try {
exitValue = p.waitFor();
} catch (InterruptedException e) {
// do something here
}

You could do the following:
Process proc = Runtime.getRuntime().exec("net start");
InputStreamReader isr = new InputStreamReader(proc.getInputStream());
BufferedReader br = new BufferedReader(isr);
String temp = null;
while (( temp = br.readLine() ) != null)
System.out.println(temp);

Take a look into ProcessBuilder.
Below Java 1.5 Runtime.getRuntime().exec(...) was used.

Java Runtime.getRuntime(): getting output from executing a command line program

I'm using the runtime to run command prompt commands from my Java program. However, I'm not aware of how I can get the output the command returns.
Here is my code:
Runtime rt = Runtime.getRuntime();
String[] commands = {"system.exe", "-send" , argument};
Process proc = rt.exec(commands);
I tried doing System.out.println(proc); but that did not return anything. The execution of that command should return two numbers separated by a semicolon. How could I get this in a variable to print out?
Here is the code I'm using now:
String[] commands = {"system.exe", "-get t"};
Process proc = rt.exec(commands);
InputStream stdIn = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(stdIn);
BufferedReader br = new BufferedReader(isr);
String line = null;
System.out.println("<OUTPUT>");
while ((line = br.readLine()) != null)
System.out.println(line);
System.out.println("</OUTPUT>");
int exitVal = proc.waitFor();
System.out.println("Process exitValue: " + exitVal);
But I'm not getting anything as my output, but when I run that command myself it works fine.

Here is the way to go:
Runtime rt = Runtime.getRuntime();
String[] commands = {"system.exe", "-get t"};
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
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);
}
Read the Javadoc for more details here. ProcessBuilder would be a good choice to use.

A quicker way is this:
public static String execCmd(String cmd) throws java.io.IOException {
java.util.Scanner s = new java.util.Scanner(Runtime.getRuntime().exec(cmd).getInputStream()).useDelimiter("\\A");
return s.hasNext() ? s.next() : "";
}
Which is basically a condensed version of this:
public static String execCmd(String cmd) throws java.io.IOException {
Process proc = Runtime.getRuntime().exec(cmd);
java.io.InputStream is = proc.getInputStream();
java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
String val = "";
if (s.hasNext()) {
val = s.next();
}
else {
val = "";
}
return val;
}
I know this question is old but I am posting this answer because I think this may be quicker.
Edit (For Java 7 and above)
Need to close Streams and Scanners. Using AutoCloseable for neat code:
public static String execCmd(String cmd) {
String result = null;
try (InputStream inputStream = Runtime.getRuntime().exec(cmd).getInputStream();
Scanner s = new Scanner(inputStream).useDelimiter("\\A")) {
result = s.hasNext() ? s.next() : null;
} catch (IOException e) {
e.printStackTrace();
}
return result;
}

If use are already have Apache commons-io available on the classpath, you may use:
Process p = new ProcessBuilder("cat", "/etc/something").start();
String stderr = IOUtils.toString(p.getErrorStream(), Charset.defaultCharset());
String stdout = IOUtils.toString(p.getInputStream(), Charset.defaultCharset());

At the time of this writing, all other answers that include code may result in deadlocks.
Processes have a limited buffer for stdout and stderr output. If you don't listen to them concurrently, one of them will fill up while you are trying reading the other. For example, you could be waiting to read from stdout while the process is waiting to write to stderr. You cannot read from the stdout buffer because it is empty and the process cannot write to the stderr buffer because it is full. You are each waiting on each other forever.
Here is a possible way to read the output of a process without a risk of deadlocks:
public final class Processes
{
private static final String NEWLINE = System.getProperty("line.separator");
/**
* #param command the command to run
* #return the output of the command
* #throws IOException if an I/O error occurs
*/
public static String run(String... command) throws IOException
{
ProcessBuilder pb = new ProcessBuilder(command).redirectErrorStream(true);
Process process = pb.start();
StringBuilder result = new StringBuilder(80);
try (BufferedReader in = new BufferedReader(new InputStreamReader(process.getInputStream())))
{
while (true)
{
String line = in.readLine();
if (line == null)
break;
result.append(line).append(NEWLINE);
}
}
return result.toString();
}
/**
* Prevent construction.
*/
private Processes()
{
}
}
The key is to use ProcessBuilder.redirectErrorStream(true) which will redirect stderr into the stdout stream. This allows you to read a single stream without having to alternate between stdout and stderr. If you want to implement this manually, you will have to consume the streams in two different threads to make sure you never block.

Also we can use streams for obtain command output:
public static void main(String[] args) throws IOException {
Runtime runtime = Runtime.getRuntime();
String[] commands = {"free", "-h"};
Process process = runtime.exec(commands);
BufferedReader lineReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
lineReader.lines().forEach(System.out::println);
BufferedReader errorReader = new BufferedReader(new InputStreamReader(process.getErrorStream()));
errorReader.lines().forEach(System.out::println);
}

#Senthil and #Arend answer (https://stackoverflow.com/a/5711150/2268559) mentioned ProcessBuilder. Here is the example using ProcessBuilder with specifying environment variables and working folder for the command:
ProcessBuilder pb = new ProcessBuilder("ls", "-a", "-l");
Map<String, String> env = pb.environment();
// If you want clean environment, call env.clear() first
//env.clear();
env.put("VAR1", "myValue");
env.remove("OTHERVAR");
env.put("VAR2", env.get("VAR1") + "suffix");
File workingFolder = new File("/home/user");
pb.directory(workingFolder);
Process proc = pb.start();
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);

Create class :
public class Utils {
public static final String SHEL_EXECUTE_ERROR = "SHEL_EXECUTE_ERROR";
public static String shellExec(String cmdCommand) {
final StringBuilder stringBuilder = new StringBuilder();
try {
final Process process = Runtime.getRuntime().exec(cmdCommand);
final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
String line;
while ((line = bufferedReader.readLine()) != null) {
stringBuilder.append(line);
}
} catch (Exception e) {
return SHEL_EXECUTE_ERROR;
}
return stringBuilder.toString();
}
}
and use:
final String shellExec = shellExec("cmd /c ver");
final String versionOS = shellExec.equals(SHEL_EXECUTE_ERROR) ? "empty" : shellExec;

If you write on Kotlin, you can use:
val firstProcess = ProcessBuilder("echo","hello world").start()
val firstError = firstProcess.errorStream.readBytes().decodeToString()
val firstResult = firstProcess.inputStream.readBytes().decodeToString()

Adapted from the previous answer:
public static String execCmdSync(String cmd, CmdExecResult callback) throws java.io.IOException, InterruptedException {
RLog.i(TAG, "Running command:", cmd);
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec(cmd);
//String[] commands = {"system.exe", "-get t"};
BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));
BufferedReader stdError = new BufferedReader(new InputStreamReader(proc.getErrorStream()));
StringBuffer stdOut = new StringBuffer();
StringBuffer errOut = new StringBuffer();
// 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);
stdOut.append(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);
errOut.append(s);
}
if (callback == null) {
return stdInput.toString();
}
int exitVal = proc.waitFor();
callback.onComplete(exitVal == 0, exitVal, errOut.toString(), stdOut.toString(), cmd);
return stdInput.toString();
}
public interface CmdExecResult{
void onComplete(boolean success, int exitVal, String error, String output, String originalCmd);
}

Pretty much the same as other snippets on this page but just organizing things up over an function, here we go...
String str=shell_exec("ls -l");
The Class function:
public String shell_exec(String cmd)
{
String o=null;
try
{
Process p=Runtime.getRuntime().exec(cmd);
BufferedReader b=new BufferedReader(new InputStreamReader(p.getInputStream()));
String r;
while((r=b.readLine())!=null)o+=r;
}catch(Exception e){o="error";}
return o;
}

Process p = Runtime.getRuntime().exec("ping google.com");
p.getInputStream().transferTo(System.out);
p.getErrorStream().transferTo(System.out);

Try reading the InputStream of the runtime:
Runtime rt = Runtime.getRuntime();
String[] commands = {"system.exe", "-send", argument};
Process proc = rt.exec(commands);
BufferedReader br = new BufferedReader(
new InputStreamReader(proc.getInputStream()));
String line;
while ((line = br.readLine()) != null)
System.out.println(line);
You might also need to read the error stream (proc.getErrorStream()) if the process is printing error output. You can redirect the error stream to the input stream if you use ProcessBuilder.

Develop Reference

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

java input.readLine hangs after starting a powershell script - java

Related

How to execute commands inside a shell using Process object in Java

Run system commands in java

Java: Pass values to the jar using OutputStreamWriter

Java run Windows command line command returning a value

Java Runtime.getRuntime(): getting output from executing a command line program

Categories

Resources