Making a System Call in Java

This is an example on how to make a system call to the local operating system to execute external programs. This example was written to work on Mac OS X, but will work on other UNIX type operating systems likely without issue. It will not work as written on Windows unless Cygwin is installed and in the PATH.

  1 /*
  2  * $Id: SystemCallExample.java 106 2008-08-30 00:58:59Z jyeary $
  3  * 
  4  * Software License Agreement (BSD License)
  5  * 
  6  * Copyright (c) 2008, Blue Lotus Software, LLC
  7  * All rights reserved.
  8  * 
  9  * Redistribution and use of this software in source and binary forms, with or
 10  * without modification, are permitted provided that the following conditions 
 11  * are met:
 12  * 
 13  *   Redistributions of source code must retain the above
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 15  *   following disclaimer.
 16  * 
 17  *   Redistributions in binary form must reproduce the above
 18  *   copyright notice, this list of conditions and the
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 22  *   Neither the name of Blue Lotus Software, LLC nor the names of its
 23  *   contributors may be used to endorse or promote products
 24  *   derived from this software without specific prior
 25  *   written permission of Blue Lotus Software, LLC
 26  * 
 27  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
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 36 package com.bluelotussoftware.examples;
 37 
 38 import java.io.BufferedInputStream;
 39 import java.io.BufferedReader;
 40 import java.io.IOException;
 41 import java.io.InputStream;
 42 import java.io.InputStreamReader;
 43 
 44 /**
 45  * This is a demo application on how to use Java to make system calls. 
 46  * The use of system calls is platform specific. This code may not be 
 47  * transportable accross platforms,i.e. UNIX, Mac OS X, and Windows.
 48  * @author John Yeary
 49  * @version 1.0
 50  */
 51 public class SystemCallExample {
 52 
 53     /**
 54      * Creates a new instance of SystemCallExample
 55      */
 56     public SystemCallExample() {
 57     }
 58 
 59     /**
 60      * Main program method
 61      * @param args the command line arguments
 62      */
 63     public static void main(String[] args) {
 64         Runtime r = Runtime.getRuntime();
 65 
 66         try {
 67             /*
 68              * Here we are executing the UNIX command ls for directory listing. 
 69              * The format returned is the long format which includes file 
 70              * information and permissions.
 71              */
 72             Process p = r.exec("ls -l");
 73             InputStream in = p.getInputStream();
 74             BufferedInputStream buf = new BufferedInputStream(in);
 75             InputStreamReader inread = new InputStreamReader(buf);
 76             BufferedReader bufferedreader = new BufferedReader(inread);
 77 
 78             // Read the ls output
 79             String line;
 80             while ((line = bufferedreader.readLine()) != null) {
 81                 System.out.println(line);
 82             }
 83             // Check for ls failure
 84             try {
 85                 if (p.waitFor() != 0) {
 86                     System.err.println("exit value = " + p.exitValue());
 87                 }
 88             } catch (InterruptedException e) {
 89                 System.err.println(e);
 90             } finally {
 91                 // Close the InputStream
 92                 bufferedreader.close();
 93                 inread.close();
 94                 buf.close();
 95                 in.close();
 96             }
 97         } catch (IOException e) {
 98             System.err.println(e.getMessage());
 99         }
100     }
101 }
102