Java Tip of the Day: Using ProcessBuilder to Make System Calls

A few years ago I posted an article on how to execute OS level system calls using the Runtime class. When I wrote that article I was using a methodology which has been around since the 1.0 days of Java. In Java 5 Standard Edition, and subsequently improved in Java 6 and Java 7, is a class called ProcessBuilder. This class is a significant improvement over using the Runtime class. It provides complete flexibilty around the system call in terms of environment including directories, input and output streams, and execution.

Here is the NetBeans 7.1 Apache Maven project: process-builder-example.zip

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/*  * Copyright 2011 Blue Lotus Software, LLC.  * Copyright 2011 John Yeary <jyeary@bluelotussoftware.com>.  *  * Licensed under the Apache License, Version 2.0 (the "License");  * you may not use this file except in compliance with the License.  * You may obtain a copy of the License at  *  *      http://www.apache.org/licenses/LICENSE-2.0  *  * Unless required by applicable law or agreed to in writing, software  * distributed under the License is distributed on an "AS IS" BASIS,  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  * See the License for the specific language governing permissions and  * limitations under the License.  */ package com.bluelotussoftware.example;   import java.io.IOException; import java.io.InputStream; import java.io.OutputStream;   /**  * <p> {@link java.lang.ProcessBuilder} Example Application to execute commands  * from command line arguments.</p> *  * @author John Yeary <jyeary@bluelotussoftware.com>  * @version 1.0  */ public class App {       private static void copy(InputStream in, OutputStream out) throws IOException {         while (true) {             int c = in.read();             if (c == -1) {                 break;             }             out.write((char) c);         }     }       public static void main(String[] args) throws IOException, InterruptedException {           if (args.length == 0) {             System.out.println("You must supply at least one argument.");             return;         }           ProcessBuilder processBuilder = new ProcessBuilder(args);         processBuilder.redirectErrorStream(true);           Process process = processBuilder.start();         copy(process.getInputStream(), System.out);         process.waitFor();         System.out.println("Exit Status : " + process.exitValue());     } }

When I execute it from NetBeans I get something like this:

[exec:exec]
total 24
drwxr-xr-x  12 jyeary  staff   408B Dec 15 08:19 .hg
-rw-r--r--   1 jyeary  staff    52B Dec 15 08:08 .hgignore
-rw-r--r--   1 jyeary  staff   1.7K Dec 15 07:59 nbactions.xml
-rw-r--r--   1 jyeary  staff   2.0K Dec 15 08:19 pom.xml
drwxr-xr-x   4 jyeary  staff   136B Dec 14 23:31 src
drwxr-xr-x   4 jyeary  staff   136B Dec 15 08:35 target
Exit Status : 0