FindExecutable.java

/**
 *  Copyright 2007-2008 University Of Southern California
 *
 *  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 edu.isi.pegasus.common.util;

import java.io.File;

/**
 * A convenience class that allows us to determine the path to an executable
 *
 * @author Jens Voeckler
 * @author Karan Vahi
 * @version $Revision$
 */
public class FindExecutable {

    /**
     * Finds the path to an executable of a given name , based on the value of
     * PATH environment variable and variable PEGASUS_BIN_DIR .
     * 
     * @param name    the name of the executable to search for.
     * 
     * @return the File object corresponding to the executable if found, else
     *         null
     */
    public static File findExec( String name ) {
        //pick up value of PEGASUS_BIN_DIR
        //the wrapper script sets value of PEGASUS_BIN_DIR as
        //java property pegasus.home.bindir .
        return FindExecutable.findExec( System.getProperty( "pegasus.home.bindir" ), name ) ;
    }
    
    /**
     * Finds the path to an executable of a given name , based on the value of
     * PATH environment variable and any additional directory that is preferred
     * to be searched for
     * 
     * @param directory the directory to search the executable in, before 
     *                  searching for in the PATH.
     * @param name    the name of the executable to search for.
     * 
     * @return the File object corresponding to the executable if found, else
     *         null
     */
    public static File findExec( String directory, String name ) {
        if ( name == null ) {
            return null;
        }

        String path = System.getenv("PATH");
        
        if( directory != null ){
            path = (path == null )? directory : directory + ":" + path;
        }
        
        if( path == null ){
            return null;
        }
        
        String[] list = path.split( ":" );
        
        for ( int i=0; i < list.length; ++i ) {
            File result = new File( list[i], name );
            if ( result.isFile() && result.canExecute() ){
                return result;
            }
        }

        return null;
    }

    /**
     * Test function for the class
     *
     * @param args
     */
    public static void main(String args[]) {
        for (int i = 0; i < args.length; ++i) {
            File f = FindExecutable.findExec( args[i] );
            if (f == null) {
                System.out.println(args[i] + " not found");
            } else {
                System.out.println(args[i] + " -> " + f);
            }
        }
    }
}