How to check if a file is open by another process (Java/Linux)?

Question

I am trying to check if a certain java.io.File is open by an external program. On windows I use this simple trick:

try {     FileOutputStream fos = new FileOutputStream(file);     // -> file was closed } catch(IOException e) {     // -> file still open } 

I know that unix based systems allow to open files in multiple processes... Is there a similar trick to achieve the same result for unix based systems ?

Any help / hack highly appreciated :-)

Answer 1

Here's a sample how to use lsof for unix based systems:

public static boolean isFileClosed(File file) {     try {         Process plsof = new ProcessBuilder(new String[]{"lsof", "|", "grep", file.getAbsolutePath()}).start();         BufferedReader reader = new BufferedReader(new InputStreamReader(plsof.getInputStream()));         String line;         while((line=reader.readLine())!=null) {             if(line.contains(file.getAbsolutePath())) {                                             reader.close();                 plsof.destroy();                 return false;             }         }     } catch(Exception ex) {         // TODO: handle exception ...     }     reader.close();     plsof.destroy();     return true; } 

Hope this helps.

Answer 2

You can run from Java program the lsof Unix utility that tells you which process is using a file, then analyse its output. To run a program from Java code, use, for example, Runtime, Process, ProcessBuilder classes. Note: your Java program won't be portable in this case, contradicting the portability concept, so think twice whether you really need this :)