Question

我正在尝试检查某个java.io.File是否由外部程序打开。在Windows上我使用这个简单的技巧：

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

我知道基于unix的系统允许在多个进程中打开文件...是否有类似的技巧可以为基于unix的系统实现相同的结果？

任何帮助/黑客高度赞赏： - ）

Answer 1

以下是基于unix的系统如何使用 lsof 的示例：

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;
}

希望这有帮助。

Answer 2

您可以从Java程序运行lsof Unix实用程序，该实用程序可以告诉您哪个进程正在使用文件，然后分析其输出。要从Java代码运行程序，请使用例如Runtime，Process，ProcessBuilder类。注意：在这种情况下，您的Java程序将无法移植，这与可移植性概念相矛盾，因此请三思而后行是否真的需要：）

Answer 3

这个也适用于Windows系统。但是注意，对Linux不起作用！

     private boolean isFileClosed(File file) {  
            boolean closed;
            Channel channel = null;
            try {
                channel = new RandomAccessFile(file, "rw").getChannel();
                closed = true;
            } catch(Exception ex) {
                closed = false;
            } finally {
                if(channel!=null) {
                    try {
                        channel.close();
                    } catch (IOException ex) {
                        // exception handling
                    }
                }
            }
            return closed;
    }

Answer 4

您可以通过@ZZ Coder

尝试使用此信号量类型代码进行文件锁定

File file = new File(fileName);
FileChannel channel = new RandomAccessFile(file, "rw").getChannel();

FileLock lock = channel.lock();
try {
    lock = channel.tryLock();
    // Ok. You get the lock
} catch (OverlappingFileLockException e) {
    // File is open by someone else
  } finally {
   lock.release();
}

Answer 5

感谢您的原始建议。我有一个小升级对这个方法有点重要：

FileOutputStream fos = null;
try {
    // Make sure that the output stream is in Append mode. Otherwise you will
    // truncate your file, which probably isn't what you want to do :-) 
    fos = new FileOutputStream(file, true);
    // -> file was closed
} catch(IOException e) {
    // -> file still open
} finally {
    if(fos != null) {
    try {
        fos.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

干杯， Gumbatron

如何检查文件是否被另一个进程（Java / Linux）打开？

5 个答案: