1 /*
   2  * Copyright (c) 2014, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 import java.io.File;
  25 import java.util.HashMap;
  26 import java.util.Map;
  27 
  28 /**
  29  * Utility class for finding the command on the current system
  30  */
  31 public class UnixCommands {
  32 
  33     public static final boolean isUnix = ! System.getProperty("os.name").startsWith("Windows");
  34     public static final boolean isLinux = System.getProperty("os.name").startsWith("Linux");
  35 
  36     private static final String[] paths = {"/bin", "/usr/bin"};
  37 
  38     private static Map<String,String> nameToCommand = new HashMap<>(16);
  39 
  40     /**
  41      * Throws Error unless every listed command is available on the system
  42      */
  43     public static void ensureCommandsAvailable(String... commands) {
  44         for (String command : commands) {
  45             if (findCommand(command) == null) {
  46                 throw new Error("Command '" + command + "' not found; bailing out");
  47             }
  48         }
  49     }
  50 
  51     /**
  52      * If the path to the command could be found, returns the command with the full path.
  53      * Otherwise, returns null.
  54      */
  55     public static String cat()   { return findCommand("cat"); }
  56     public static String sh()    { return findCommand("sh"); }
  57     public static String kill()  { return findCommand("kill"); }
  58     public static String sleep() { return findCommand("sleep"); }
  59     public static String tee()   { return findCommand("tee"); }
  60     public static String echo()  { return findCommand("echo"); }
  61 
  62     public static String findCommand(String name) {
  63         if (nameToCommand.containsKey(name)) {
  64             return nameToCommand.get(name);
  65         }
  66         String command = findCommand0(name);
  67         nameToCommand.put(name, command);
  68         return command;
  69     }
  70 
  71     private static String findCommand0(String name) {
  72         for (String path : paths) {
  73             File file = new File(path, name);
  74             if (file.canExecute()) {
  75                 return file.getPath();
  76             }
  77         }
  78         return null;
  79     }
  80 }