如何检查文件是否被另一个进程（Java/Linux）打开？
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How to check if a file is open by another process (Java/Linux)?
提问by salocinx
I am trying to check if a certain java.io.File is open by an external program. On windows I use this simple trick:
我正在尝试检查某个 java.io.File 是否被外部程序打开。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
}
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 ?
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？
Any help / hack highly appreciated :-)
任何帮助/黑客高度赞赏:-)
回答by Aishwarya Shiva
You can try this semaphore type code for a file lock by @ZZ Coder
您可以通过@ZZ Coder 尝试使用此信号量类型代码来锁定文件
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();
}
回答by Alexey Berezkin
You can run from Java program the lsofUnix 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, ProcessBuilderclasses. Note: your Java program won't be portable in this case, contradicting the portability concept, so think twice whether you really need this :)
您可以从 Java 程序运行lsofUnix 实用程序，该实用程序会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 程序将不可移植，这与可移植性概念相矛盾，因此请三思您是否真的需要这个 :)
回答by Hans Frankenstein
Here's a sample how to use lsoffor unix based systems:
以下是如何将lsof用于基于 unix 的系统的示例：
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;
}
Hope this helps.
希望这可以帮助。
回答by Gumbatron
Thanks for the original suggestion. I have one small upgrade that is somewhat important to that method:
感谢您的原始建议。我有一个小升级，它对该方法有些重要：
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();
}
}
Cheers, Gumbatron
干杯，Gumbatron
回答by salocinx
This one should also work for Windows systems. But attention, does not work for Linux!
这个也应该适用于 Windows 系统。但请注意，不适用于 Linux！
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;
}
