Develop Reference

ProcessBuilder failing when calling a system command where Runtime exec works

I'm having trouble with ProcessBuilder not running a command on the server.
Early in my project I use Runtime.exec() just to retrieve output from a program which works fine:
private List<SatelliteCode> getSatelliteCodes() {
List<SatelliteCode> codes = new ArrayList<>();
Runtime runtime = Runtime.getRuntime();
String[] commands = { "w_scan", "-s?" };
Process process;
try {
process = runtime.exec(commands);
BufferedReader error = new BufferedReader(new InputStreamReader(process.getErrorStream()));
String s = error.readLine(); // discard first line
while ((s = error.readLine()) != null) {
s = s.trim();
int i = s.indexOf('\t'); // separated by a tab!?!?
codes.add(new SatelliteCode(s.substring(0, i), s.substring(i)));
}
} catch (IOException e) {
e.printStackTrace();
}
return codes;
}
Running this in the terminal works fine and I get all the output I need:
w_scan -fs -cGB -sS19E2 > channels.conf
However, the server needs to grab the ongoing output from the 'process.getErrorStream()' to display in the web interface. What is actually happening is the ProcessBuilder is failing and returning an exit code of 1.
The function that initialises the ProcessBuilder and to start the scan running is [EDIT 1]:
private static StringBuilder scan_error_output = null;
#Override
public boolean startSatelliteScan(String user, String country_code, String satellite_code) {
UserAccountPermissions perm = validateUserEdit(user);
if (perm == null) return false;
Shared.writeUserLog(user, Shared.getTimeStamp() +
": DVB satellite scan started " +
country_code + " - " + satellite_code +
System.lineSeparator() + System.lineSeparator());
scan_error_output = new StringBuilder();
new ScanThread(country_code, satellite_code).start();
// write out country code and satellite code to prefs file
BufferedWriter bw = null;
try {
bw = new BufferedWriter(new FileWriter(satellite_last_scan_codes));
bw.write(country_code); bw.newLine();
bw.write(satellite_code); bw.newLine();
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
return true;
}
That will then run two other threads on the server, one that will run the scan itself and wait for it to finish so that it can get the final scan data. And the other which constantly updates the output from the std error stream which is then polled at intervals from the clients browser. This is much like showing the ongoing output from the terminal.
The scan thread (which fails to start the process) [EDIT 1]:
private static class ScanThread extends Thread {
private String cc, sc;
public ScanThread(String country_code, String satellite_code) {
cc = country_code;
sc = satellite_code;
}
public void run() {
ProcessBuilder pb = new ProcessBuilder("/usr/bin/w_scan",
"-fs", "-c" + cc, "-s" + sc);
pb.redirectOutput(new File(satellite_scan_file));
Process process;
try {
System.out.println("Scan thread started");
process = pb.start();
IOScanErrorOutputHandler error_output_handler = new IOScanErrorOutputHandler(process.getErrorStream());
error_output_handler.start();
int result = process.waitFor();
System.out.println(cc + " - " + sc + " - " +
"Process.waitFor() result " + result);
} catch (IOException e) {
System.out.println(e.getMessage());
e.printStackTrace();
} catch (InterruptedException e) {
System.out.println(e.getMessage());
e.printStackTrace();
}
System.out.println("Scan thread finished");
}
}
The error output stream thread which captures the output which obviously doesn't start due to the scan thread failing:
private static class IOScanErrorOutputHandler extends Thread {
private InputStream inputStream;
IOScanErrorOutputHandler(InputStream inputStream) {
this.inputStream = inputStream;
}
public void run() {
Scanner br = null;
try {
System.out.println("Scan thread Error IO capture running");
br = new Scanner(new InputStreamReader(inputStream));
String line = null;
while (br.hasNextLine()) {
line = br.nextLine();
scan_error_output.append(line + System.getProperty("line.separator"));
}
} finally {
br.close();
}
System.out.println("Scan thread Error IO capture finished");
scan_error_output = null;
}
}
And the server function which returns the std error output progress:
#Override
public String pollScanResult(String user) {
if (validateUserEdit(user) == null) return null;
StringBuilder sb = scan_error_output; // grab instance
if (sb == null) return null;
return sb.toString();
}
As mentioned above, Runtime.exec() works fine, but the ProcessBuilder is failing.
NB: I'm on Linux Mint 18.1, using Apache Tomcat 8 as the server, linux default JDK 8 and GWT 2.7 [Correction from 2.8] in Eclipse Neon.
Can anyone see what I am doing wrong?
Many thanks in advance...
[EDIT 1]
Whilst developing this on another machine, Linux Mint 17.2, JDK 8 and Apache Tomcat 7, for DVB-T, this method worked fine and polling for the scan output showed up in the client's browser.
The ProcessBuilder.start still returns 1 and an empty file is created for the output scan file.
[EDIT 2]
It appears that the reason the ProcessBuilder is failing is because the user 'tomcat8' doesn't have permissions to run 'w_scan'. 'w_scan' works from the terminal, but not from the tomcat server. Somehow I've got to fix that now.
[SOLUTIONS]
After being put in the right direction by VGR for getting the error stream from the ProcessBuilder, I started digging further and found I was getting:
main:3909: FATAL: failed to open '/dev/dvb/adapter0/frontend0': 13 Permission denied
Apache tomcat 8 didn't have permission to access the DVB-S frontend to run a scan. This was fixed in two ways:
1 - 03catalina.policy I added the extra permissions (whether they made a difference I do not know).
grant codeBase "file:/dev/dvb/-" {
permission java.io.FilePermission "file:/dev/dvb/-", "read, write";
permission java.security.AllPermission;
};
2 - The dvb frontends belong to the 'video' group. So I needed to add the user tomcat8 to that group.
usermod -a -G video tomcat8
All works for now...

You are not doing the same thing with ProcessBuilder that you’re doing with Runtime.exec, so I don't know why you think ProcessBuilder is the problem.
You have a few problems with how you’re writing the command’s output to a file.
First, the presence of ">", satellite_scan_temp_file in your ProcessBuilder command is incorrect. Output redirection is not part of any command; it is handled by a shell. But when you run with Runtime.exec or ProcessBuilder, you are not running in a shell, you are executing the process directly. Neither w_scan nor any other command considers > a special character.
The correct way to redirect to a file is with the redirectOutput method:
ProcessBuilder pb = new ProcessBuilder(
"/usr/bin/w_scan", "-fs", "-s" + satellite_code, "-c" + country_code);
pb.redirectOutput(new File(satellite_scan_temp_file));
Second, your ScanThread code is ignoring the (currently incorrect) redirect, and is attempting to read the command’s output. But there is no output, because you are redirecting it all to a file.
Once you are properly redirecting output to a file, you can remove your BufferedReader and BufferedWriter loops completely.
Finally, it is worth noting that the error output you captured probably told you that > is not a valid argument to the w_scan process.

Compiling Java program with VBScripts? (NetBeans)

I have a Java program created that runs VBSscripts after button clicks.
examplescript.vbs
How do I compile these vbs files and then call them to run in the program code? I've been troubleshooting for several days and can't find an answer. Once again I need to be able to run these scripts, at one point I had an input stream created to it but couldn't get it as a vbs file. Hopefully I'm overlooking something here
Edit:
This is what I currently have. With this code I receive the error "Windows Script Host. There is no script extension for file extension ".BufferedInputStream#4e34904""
ClassLoader classloader = Thread.currentThread().getContextClassLoader();
InputStream is = classloader.getResourceAsStream("hello.vbs");
try {
Runtime.getRuntime().exec("wscript " + is);
}
catch( IOException e ) {
System.out.println(e);
System.exit(0);
}
System.out.print(is);

You can run your VBScript as below.
Runtime.getRuntime().exec( "wscript path/to/examplescript.vbs" );

As already mentioned, VBScript is a script and doesn't need compiling. If you want to run code written in VBScript then you can do it this way:
This example uses VBScript to get the Motherboard Serial Number of a computer that is running Microsoft Windows:
try {
// Create a temporary script file named MBSerialxxxxxxxx.vbs
File file = File.createTempFile("MBSerial",".vbs");
// Delete the temporary file when virtual machines terminates
file.deleteOnExit();
try (FileWriter fw = new java.io.FileWriter(file)) {
String vbs = "Set objWMIService = GetObject(\"winmgmts:\\\\.\\root\\cimv2\")\n"
+ "Set colItems = objWMIService.ExecQuery _ \n"
+ " (\"Select * from Win32_BaseBoard\") \n"
+ "For Each objItem in colItems \n"
+ " Wscript.Echo objItem.SerialNumber \n"
+ " exit for ' do the first cpu only! \n"
+ "Next \n";
fw.write(vbs);
}
// Run the VBScript file....
Process p = Runtime.getRuntime().exec("cscript //NoLogo " + file.getPath());
// Read in any output to the command window.
BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while ((line = input.readLine()) != null) {
// display the output...
System.out.println(line.trim());
}
input.close();
}
catch(IOException e){
e.printStackTrace();
}

Running a .exe file from a Java web app doesn't work

I'm trying to run a .exe file develop in Pascal from my web app(Windows + Primefaces 5 + Tomcat 8). The program generate a text file that I'm gonna read it after but it seems it doens't have the permission to do that, no exceptions were threw.
Here is how I pick the path:
String path = FacesContext.getCurrentInstance().getExternalContext().getRealPath("/WEB-INF/lib/");
projeto.setQtde(1);
this.esquemas = gerenciarProjeto.realizarCorte(projeto, usuario, path+"/");
and here is how I call the program:
Runtime rt = Runtime.getRuntime();
Process pc = rt.exec(this.caminho+"cortebi.exe");
InputStreamReader isr = new InputStreamReader(pc.getErrorStream());
BufferedReader br = new BufferedReader(isr);
String line = null;
System.out.println("<ERROR>");
while ( (line = br.readLine()) != null){
System.out.println(line);
}
System.out.println("</ERROR>");
int exitVal = pc.waitFor();
System.out.println("Process exitValue: " + exitVal);
I realized that if I put the .exe file into my project root and run Eclipse as administrator it works. But I do not know how to put it into my web app root to do the same after it's deployed, I've tried to put it in diferent locations and nothing!

I was able to figure out what was the problem. I tought that Runtime.getRuntime().exec() would behave like a tradicional DOS prompt but I was wrong. In fact the problem itself was not a windows or file permission problem but a misconception of how the exec() method works. I wrote a new piece of code:
public void executarCortebi(File file){
try {
Process pc = Runtime.getRuntime().exec("cmd /c start cortebi.exe",null, file);
StreamGobbler error = new StreamGobbler(pc.getErrorStream(), "ERRO");
StreamGobbler output = new StreamGobbler(pc.getInputStream(), "OUTPUT");
error.start();
output.start();
pc.waitFor();
Thread.sleep(800);
} catch (IOException e) {
e.printStackTrace();
}catch(InterruptedException e) {
e.printStackTrace();
}
}
As I said the way the exec() method works is more restricted I found good material here:When Runtime.exec() won't.
Explaining the parameters of getRuntime.exec() used for me, we have the fallow: First the command itself that must be executed(It's noticeable the diferences between the old cold and the new one), second are the arguments for the .exe file wich in this case are none and third is the file that has the path from my .exe program.
Now everything is working!

How to run application with parameters from within java application on mac osx

I am writing a small java application to load ZDoom with custom wad files on mac osx and am having trouble executing the command.
I have generated a string within the application that will run ZDoom and load the custom wad, I have tested this by copy-pasting the string from the netbeans breakline debugger and running it directly in terminal.
When I run the code through my application ZDoom does load up but it does so without the custom wad so I believe it is executing without it's arguments.
I have tried two different techniques to run the command:
private void loadZdoom() {
// get selected wad
String wad = (String) wadListComboBox.getSelectedItem();
ProcessBuilder builder = new ProcessBuilder(defaultZdoomInstallPath + "/Contents/MacOS/zdoom", "-file", defaultZdoomWadsPath.replace(" ", "\\ ") + "/" + wad);
builder.redirectErrorStream(true);
try {
Process p = builder.start();
} catch (IOException ex) {
}
}
And
private void loadZdoom() {
// get selected wad
String wad = (String) wadListComboBox.getSelectedItem();
String runCommand = defaultZdoomInstallPath + "/Contents/MacOS/zdoom " + "-file " + defaultZdoomWadsPath.replace(" ", "\\ ") + "/" + wad;
try {
Runtime runTime = Runtime.getRuntime();
Process process = runTime.exec(runCommand);
} catch (IOException e) {
}
}
What am I doing wrong here?

I figured out what the problem was, I was escaping the space in the path to the wad file as you need to do this in terminal but it seems this is unnecessary in JAVA. All is working as expected now :)

Command line argument works in console, fails from within Runtime.getRuntime().exec

Trying to build a basic launcher for a java game. I'm building the proper command to run the application. When the following command executes in the launcher, the launcher closes as expected, but the command doesn't appear to work - either it doesn't work or the game launches and immediately crashes.
When I print this same command to the console and copy/paste it into console and execute manually, it works perfectly.
/**
*
*/
protected void launch(){
currentStatusMsg = "Launching...";
String cmd = "java -jar";
cmd += " -Djava.library.path=\"" +nativesDirectory.getAbsolutePath() + "\"";
cmd += " \""+applicationJar.getAbsolutePath() + "\"";
System.out.println(cmd);
try {
Runtime rt = Runtime.getRuntime();
Process pr = rt.exec(cmd);
//closeLauncher();
BufferedReader input = new BufferedReader(new InputStreamReader(pr.getInputStream()));
String line=null;
while((line=input.readLine()) != null) {
System.out.println(line);
}
int exitVal = pr.waitFor();
System.out.println("Exited with error code "+exitVal);
} catch(Exception e) {
System.out.println(e.toString());
e.printStackTrace();
}
}
I tried adding something to read the output, but nothing is printed.
I was originally using the following format instead, but it has the same effect:
Process pr = Runtime.getRuntime().exec(new String[]{
"java",
"-Djava.library.path=\"" +nativesDirectory.getAbsolutePath() + "\"",
"-jar",
applicationJar.getAbsolutePath()});
Update I realized I was closing the launcher before allowing the debug code to run. The system only prints: "Exited with error code 1"
I finally was able to get the subprocess error to print. It states:
Exception in thread "main" java.lang.UnsatisfiedLinkError: no lwjgl in java.library.path
However, it should be available because the command I'm executing includes the library path, and when this exact command is run manually, it works fine.

the java command launcher is not a shell. don't use quoting and space separated commands because it won't end well. put each argument into a separate String without any extra quoting, and use the exec(String[]) method.