Using ProcessBuilder with argument list as single String

Question

I try to switch from Runtime.exec(command) to ProcessBuilder for executing ImageMagick's convert from a Java programm. The options for convert are passed-in from the user as a String, so I cannot easily separate the arguments to pass them indvidually to ProcessBuilder's constructor. The actual command that works on the (Unix) commandline is

convert -colorspace gray -enhance -density 300 in.pdf out.pdf

How can I get this could to work:

public class Demo {
    public static void main(String[] args) throws IOException, InterruptedException {
        String convertOptions = "-colorspace gray -enhance -density 300"; // arguments passed in at runtime
        ProcessBuilder bp = new ProcessBuilder(new String []{"convert",convertOptions,"in.pdf","out.pdf"});
        Process process = bp.start();
        process.waitFor();
    }
}

Currently, the code justs run

Split convertOptions with " " as delims and use them to construct convertOptions? If you pass the whole string , it will consider whole string as a parameter. Its not what you want I presume. — SomeDude
– SomeDude, Commented Feb 6, 2016 at 14:57
you are right of cause, but I do not need to split on " ", but on "-" — Raphael Roth
– Raphael Roth, Commented Feb 8, 2016 at 6:51

dariober · Accepted Answer · 2017-04-16 11:05:55Z

3

Old question but since I'm facing a similar situation...

If you don't want to split the command string into an array you could execute the whole string using bash -c:

String convert= "convert -colorspace gray -enhance -density 300";
String[] cmd= new String[] {"bash", "-c", convert};
ProcessBuilder builder = new ProcessBuilder(cmd);
...

This of course assumes bash is available.

answered Apr 16, 2017 at 11:05

dariober

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SomeDude · Accepted Answer · 2016-02-08 14:41:38Z

0

You could use regex to get your params like in the code below:

String regex = "((\\s*|-)\\w+)";
Pattern p = Pattern.compile(regex);
String convertOptions = "-colorspace gray -enhance -density 300"; // //arguments passed in at runtime
Matcher matcher  = p.matcher(convertOptions);
List<String> pargs = new ArrayList<String>();
pargs.add("convert");
while(matcher.find())
{
   String match = matcher.group();
   if( match != null )
   {
      pargs.add(match.trim());
   }
}
pargs.add("in.pdf");
pargs.add("out.pdf");

try
{
    ProcessBuilder bp = new ProcessBuilder( pargs.toArray(new String[]{}) );
    Process process = bp.start();
    process.waitFor();
}
catch(Exception ex)
{
  ex.printStackTrace();
}

edited Feb 8, 2016 at 14:41

answered Feb 8, 2016 at 13:30

SomeDude

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