Question

I’m having some trouble running gnuplot processes from Java. I’m creating a gnuplot script file, and then running it from within a java program. I’ve tried using both Process Builder and building a precess using Runtime.getRuntime().exec(“blah blah…”), and neither have the full capability to work. The funny thing is is that using Runtime to make the process works almost perfectly, as long as the image file I’m creating via gnuplot isn’t being saved to a directory without a space in it’s name. ProcessBuilder doesn’t work at all, however, and gives me the error: “CreateProcess error=2, The system cannot find the file specified”

It’s taken me far too long to figure this stuff out, and so any help would be appreciated.

The code I use is here:

File script = new File("Demo.plt");    //Script file that outputs to a PNG file

//This works as long as the script file doesn't output to a png with a space in it's filepath
Process aProcess = Runtime.getRuntime().exec("gnuplot " + script.toString());
Thread.currentThread().sleep(1000);
aProcess.waitFor();

//This doesn't work at all
ProcessBuilder builder = new ProcessBuilder("gnuplot " + script.toString());
builder.redirectErrorStream(true);
Process process = builder.start();

And I know that the script works if run outside of Java, regardless of the spaces in the output line. I’ve even tried using ‘\ ‘ (the escape character for a space) and that doesn’t work either. In fact, here is the code that I use:

String graphName = "DemoGraph";
//Isolate the FilePath
String path = script.getPath();
path = path.replace(script.getName(),"");
path = path.replace(File.separator, "\\\\"); //Gets around any parsing errors in filepaths on Windows
path = path.replace(" ", "\\ ");   //Should get around parsing errors with spaces in gnuplot, but it seems to be irrelevant.

scriptFileWriter.write("set output \"" + path + graphName + ".png\"\r\n");

It’s got to be an issue with java, because the scripts run from the Windows command line, and from the gnuplot command line, and frun being run by double-clicking the

Answer 1

I forgot to put quotes around the file name. It was a STUPID error.