Writing a file to unix directory

I have a web application which uploads a file from the client and stores them in a directory. This works fine in windows, but on a unix server
does not work. I am not getting a stack trace and
have changed the directory path slashes from \ to / but alas nothing. I am using Apache Tomcat 4.1 server.
Any help would be appreciated
Tony

So what is the stack trace?
- Peter

Apologies, here it is -
I am creating the file object like the following
File file = new File ("../webapps/NAMEOFWAR", "fileName");
and getting the following error
java.io.IOException: No such file or directory
at java.io.UnixFileSystem.createFileExclusively(Native Method)
at java.io.File.createNewFile(File.java:688)
at com.vetsWest.upload.UploadHelper.uploadFile(UploadHelper.java:36)
at com.vetsWest.upload.UploadAction.perform(UploadAction.java:122)
at org.apache.struts.action.ActionServlet.processActionPerform(ActionServlet.java:1786)
at com.vetsWest.VetsWestServlet.processActionPerform(VetsWestServlet.java:134)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1585)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:509)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)

Could it simply be that the current working directory is not quite what you expect it to be? What you're trying to do looks distinctly suspect and non-portable to me. AFAIK you don't get any guarantees that the web-app root or anything else is the current working directory. And as the Tomcat startup scripts under Windows and Unix are different and started in different ways, they could easily explain why the working directory is different.
A few general hints. ServletContext.getRealPath() gives the filesystem path for any web-app resource; you can perhaps navigate relative to a known resource. ServletContext.getResource() retrieves a resource URL relative to the web-app root. ServletContext.getResourceAsStream() opens an InputStream on a resource.
Beware that some application servers run your web-app straight out of the war or even out of a database. For truly portable applications, you cannot rely on getRealPath().
- Peter