I'm trying to read exit value from external program but it's always 0.
String command = ("cmd /c start /wait "+ Script[0]);
Process exec = runtime.exec(command);
int waitFor = exec.waitFor();
System.out.println(exec.exitValue); //always 0
System.out.println(waitFor); //always 0
Program is used for programming modules and I need to know if there were any error's.
How to get the application exit value?
The program you're actually running is the cmd program, not whatever you're running under that.
See How do I get the application exit code from a Windows command line? for how to extract the underlying exit code.
Related
In Java, I start one new Process using Runtime.exec(), and this process in turn spawns several child processes.
I want to be able to kill all the processes, and have previously been trying process.destroy() and process.destroyForcibly() - but the docs say that destroyForcibly() just calls destroy() in the default implementation and destroy() may not kill all subprocesses (I've tried and it clearly doesn't kill the child processes).
I'm now trying a different approach, looking up the PID of the parent process using the method suggested here and then calling ps repeatedly to traverse the PIDs of child processes, then killing them all using kill. (It only needs to run on Linux).
I've managed the first bit - looking up the PID, and am trying the following command to call ps to get the child PIDs:
String command = "/bin/ps --ppid " + pid;
Process process = new ProcessBuilder(command).start();
process.waitFor();
Unfortunately the 2nd line above is throwing an IOException, with the following message: java.io.IOException: Cannot run program "/bin/ps --ppid 21886": error=2, No such file or directory
The command runs fine if I paste it straight into the terminal on Ubuntu 16.04.
Any ideas would be very much appreciated.
Thanks
Calling the command you wish to run this way is always destined to fail.
Since Process does not effectively run a shell session, the command is basically handed over to the underlying OS to run. This means that it'll fail, since the path to t he program to be executed (in this case ps), is not the full one hence the error you're getting.
Also, testing whether your command works using a terminal is not correct. Using a terminal contains the notion of performing an action with an active logged in user with a correct path etc etc. All the above are not the case though when running a command through Process as these are not taken into consideration.
Furthermore, you also need to account for cases where the actual java application could be running under a different user, with a different set of permissions, paths etc.
In order for your to fix this, you can simply do either of the following:
1) Invoke your ps command using the full path to it (still not sure if it would work)
2) Change the way your create the Process object into something like: p = new ProcessBuilder("bash", "-c", command).start();
The second, will effectively run a bash session, passing in the ps command as an argument thus obtaining the desired result.
http://commons.apache.org/proper/commons-exec/tutorial.html
```
String line = "AcroRd32.exe /p /h " + file.getAbsolutePath();
CommandLine cmdLine = CommandLine.parse(line);
DefaultExecutor executor = new DefaultExecutor();
int exitValue = executor.execute(cmdLine);
```
I am trying to write a program that calls external jars from the command line. In my code it will do java -jar test,jar args. What I want to know though is if a error occurs in this external jar, how to catch it in my java program so I can do the necessary procedure? This is a new zone of coding for me from college level so I am a little clueless.
Command-line programs returns exit status when finished executing it's work (e.g. zero when everything is ok).
You should be able to retrieve something interesting by storing the return value of your system call and test it according to what you want to do.
// Code from https://stackoverflow.com/questions/8496494/
Runtime rt = Runtime.getRuntime();
Process pr = rt.exec("java -jar test.jar args");
// Check retVal to test
int retVal = pr.waitFor();
More about this in this SO question.
I want to run this code in java using:
process = Runtime.getRuntime().exec(str);
"cmd /c WMIC CPU GET LoadPercentage > n.txt";
If I use it in a bat file, there is no problem.
But if I put it into a Java, it just keep running until break.
Does anyone have a solution?
Running windows
You need to split the String in the .exec() parameters into multiple strings with no spaces, like this:
process = Runtime.getRuntime().exec(new String[]{"cmd", "/c", "WMIC", "CPU", "GET", "LoadPercentage", ">", "n.txt"});
And not!
I have put the above exec cmd into two bat-files in order to get a result.
Unfortunately the result first come out when I teminate the program.
For clarity: The above code is running in a "prochrun, Apace".
The first request is to get the PID using "Tasklist", that comes out with a response, working fine.
But when I request a "cmd /c WMIC CPU GET LoadPercentage > n.txt" inside another bat-file, I first get the response when I kill the process.
How do I get the response inside a running program running procrun?
Br
I have to print a PDF file in java program and make sure it's printed successfully, else throw exception.
My Code is:
Process p = Runtime.getRuntime().exec("lp -c -n 1 -d 1.2.3.4 abc.pdf");
System.out.println(p.waitFor());
Above code prints 0, but it only confirms that job is submitted fine, how to make sure that it's printed also.
Is there any other way to do this?
Run lpstat (after lp) and capture the process output.
How to exit the console of a simple Java program after displaying an error message?
currently my code has:
...
...
if (some condition){
//print error
System.exit();
...
...
But this System.exit(); leaves the console open. I have tried exit(0);, System.exit(0); as well.
If you're wanting to close the Command Prompt window that your application is running in, then I don't believe there is a way to do it (At least not nicely).
Why do you want to start your application from the command prompt and then close the pre-existing Command Prompt window? This will surely get rid of the error message that you're outputting (unless it's also being logged - in which case why print it to a window you want to close?).
This is Windows specific, but would creating a shortcut in Windows Explorer to java -jar MyJarFile.jar or java MyCompiledClass do what you want? Instructions for this sort of approach can be found here.
System.exit(1);
should work fine. Note that if you're exiting with an error, you would normally set a non-zero exit code. From the doc:
The argument serves as a status code; by convention, a nonzero status
code indicates abnormal termination.
This means you can script using common conventions, any process spawning your program can react correspondingly etc.
If I understand you correctly, you want to run your program in a command prompt and if the program fails you want it to display the error message, close the program AND the commad prompt window?
If this is the case then the only thing I could think of would to be to run your program in a batch file that checks the exit status of your program. So in your code write your error message, then I suggest sleep for a few seconds so the user can actually see it, then exit with status code 1.e.g.
if(SomeCondition){
System.err.println("ERROR MESSAGE...");
Thread.sleep(3000);//Sleep for 3 seconds...
System.exit(1);
}
Then run your program from a batch file which checks the "ERRORLEVEL" environment variable e.g.
java <INSERT_PROGRAM_NAME>
IF %ERRORLEVEL% == 1 exit
Hope this helps :)
java.lang.System doesn't have an exit method with no parameters, so System.exit(); would be a compile-error. (System.exit(1);, however, would be fine.) The reason that your code isn't working is probably that you're not recompiling it, so you're still running some old version from before you added that line.
Suppose you are trying to install firefox .bat file from java
public static void main(String[] args) throws InterruptedException {
try {
String[] command = { "cmd.exe", "/C", "Start", "C:\\firefox.bat" };
Runtime.getRuntime().exec(command).waitFor();
}
catch (Exception e)
{
System.out.println("Execution error");
}
}
This would trigger the command prompt and the window will be opened until you manually go and close it after the firefox is installed.
The fix is that in your .bat file just after your command just put an "exit" For eg:
Your firefox.bat would contain
#Start /wait "Firefox" "C:\Firefox Setup 41.0.exe" -ms
exit
This will close your command prompt window. Hope this helps...
have a look at the below link
http://www.cs.bris.ac.uk/jot/decisions/exercise11/exit.html
There is a general convention that a program must return an exit code. The exit code should be zero to indicate success, and non-zero to indicate failure. Platforms differ about what different non-zero codes mean, so programmers often just return 1 as a general indication of failure.
System.exit(); terminates the JVM. The int is the status code (0 means "normal" exit). If it's not exiting it's because that part of your code is not reachable and not being executed at all.
Java API - System.exit()