What happens if you try to delete a symbolic link from Java.

Deleting a symbolic link

Given a symbolic link of

	fileA -> fileB
	

what happens if you try to call file.delete() (the Java 'delete' command) on fileA?

To test what happens, I wrote a test program using Java1.4 on Sun Solaris 8.

Here is the program...

/* Program to test what happens if you try to delete a symbolic
 * link from java (running on Solaris)
 * 
 * Command line arguments:
 * 		filename - the symbolic link to delete. (target can be a file or a directory.)    
 */

import java.io.*; 
 
public class delete
{
public static void main(String args[])
{
	if ( args.length <= 0 )
	{
		System.out.println("You didn't specify the symbolic link to delete.");
		System.out.println("Exiting...");
		System.exit(1);
	}
	
	String link_name = args[0];
	System.out.println("Input Details...");
	System.out.println("Symbolic Link: "+link_name);
	System.out.println("");
	
	delete d = new delete(link_name);
}

/**
 * Constructor
 */ 
public delete(String link_name)
{
	if ( ! exists( link_name ) )
	{
		System.out.println( link_name + " does not exist.");
		System.out.println("Exiting...");
		System.exit(1);			
	}
	
	if ( ! isSymbolicLink( link_name ) )
	{
		System.out.println( link_name + " is not a symbolic link.");
		System.out.println("Exiting...");
		System.exit(1);		
	}
	
	if ( delete(link_name) )
	{
		System.out.println("Java's File.delete() returned OK.");
	}
	else
	{
		System.out.println("Java's File.delete() did NOT work OK.");
	}
}

private boolean exists(String link_name)
{
	File f = new File( link_name );
	return f.exists();
}

private boolean isSymbolicLink(String link_name)
{
	try
	{
		File f = new File( link_name );
		if ( ! f.getAbsolutePath().equals( f.getCanonicalPath() ) )
		{
			return true;
		}
		else
		{
			return false;
		}
	}
	catch(IOException e)
	{
		System.out.println("Exception occurred while trying to determine if " + link_name + "is a symbolic link.");
		System.out.println("Can't continue, exiting...");
		System.exit(1);
		return false;
	}
}

private boolean delete(String link_name)
{
	File f = new File(link_name);
	return f.delete();
}

} // end of class.

The result of my tests were that the symbolic link gets removed (whether the symbolic link points to a file or a directory) but the target object was left untouched.

Note: In the above code, I attempted to identify a symbolic link by comparing the file's absolute path to it's canonical path (see the 'isSymbolicLink(...)' method above). This was the method I had seen suggested several times on the web. Since implementing this method, however, I have determined that it is NOT reliable enough and I am not all that happy with it... (see the following thread in the Java secion of the forums area).