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I am trying to run a executable file generated by c in Java. Originally, I can run it on terminal with

./bin/svm-train -s 0 -t 0 -d 3 -g 0.0 -r 0.0 -n 0.5 -m 40.0 -c 1.0 -e 0.001 -p 0.1 ./data/trainfile ./model/update.model

This command on terminal works well and it will take a few seconds to generate a file 'update.model' as indicated in the code.

But when I try to put this process in Java with the following code, the program ends without generating 'update.model'

String[] cmdUpdateTrain = new String[]{"/bin/bash", "-c", "./bin/svm-train -s 0 -t 0 -d 3 -g 0.0 -r 0.0 -n 0.5 -m 40.0 -c 1.0 -e 0.001 -p 0.1 ./data/trainfile ./model/update.model"};
Runtime.getRuntime().exec(cmdUpdateTrain);

If I try with the following code with Java, it works fine the model can also be generated.

String[] cmdUpdateTrain = new String[]{"/bin/bash", "-c", "./bin/svm-train ./data/trainfile ./model/update.model"};
Runtime.getRuntime().exec(cmdUpdateTrain);

So I think it may be the problem of handling parameter for ./bin/svm-train.

I have found why it happens. It is because the program ends before the execution of ./bin/svm-train stops. And the following code fix this problem.

try{
    String[] cmdUpdateTrain = new String[]{"/bin/bash", "-c", "./bin/svm-train -s 0 -t 0 -d 3 -g 0.0 -r 0.0 -n 0.5 -m 40.0 -c 1.0 -e 0.001 -p 0.1 ./data/trainfile ./model/update.model"};
    Process psTrain = Runtime.getRuntime().exec(cmdUpdateTrain);
    psTrain.waitFor();
}catch(InterruptedException interupt){
}
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1  
You say it doesn't work. What happens when you try to run it? Do you get any error messages? Please edit your question to include this information. – Kenster Feb 8 at 13:05

1 Answer 1

up vote 0 down vote

Runtime.getRuntime().exec(cmdUpdateTrain)

Don't. Use. Runtime.exec().

You have several problems with your command line.

First of all: did you notice the beginning of your command, and the paths of your two file arguments? They are relative to the directory in which you launch your command; this is highly unlikely that this is the same directory from which your Java program is launched, so just for that it can only fail.

Second: you use a command interpreter. Why?

Third: how about stdin, stdout, stderr? Does your program output anything? If yes, how do you handle this?

The solution is, as always when running external processes in Java, to use a ProcessBuilder:

final Path basedir = Paths.get("whereyourprogramislaunched");
final Path stdout = Paths.get("somewheretooutputstdout");
final Path stderr = Paths.get("somewheretooutputstderr");

final ProcessBuilder builder = new ProcessBuilder(
    "./bin/svm-train", "-s", "0", "-t", "0", "etc", "etc"
);

pb.directory(basedir.toFile());
pb.redirectOutput(stdout.toFile());
pb.redirectError(stderr.toFile());

final Process process = builder.start();

// Deal with process exit code
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