How to rename a file to another file system?

Question

I got a strange problem on using renameTo(). I don't know why I can't rename to /mnt/desttest but it is ok to rename to /home/kit.ho/desttest. However, I already give every write permission to /mnt/. The return value is false while no specific reason. Who knows the reason?

import java.io.File;
public class renameFile {
    public static void main(String[] args) {
        File sourceFile = new File("/home/kit.ho/test");  
        File targetFile1 = new File("/mnt/desttest");  
        System.out.println("source file is exist? " + sourceFile.exists() + ", source file => " + sourceFile);  
        System.out.println(targetFile1 + " is exist? " + targetFile1.exists());  
        System.out.println("rename to " + targetFile1 + " => " + sourceFile.renameTo(targetFile1));  
        System.out.println("source file is exist? " + sourceFile.exists() + ", source file => " + sourceFile);   
    }
}

Edit: Finally, based on some answers, Rename function does not work on across file system, is there any workaround on this issue by not calling external command like "mv"?

Can you `mv /home/kit.ho/test /mnt/desttest` without problems? — Martin, Aug 17 '11 at 03:54
@Kit Ho: You *aren't* renaming a file; you're *moving* it across partitions. — Mechanical snail, Aug 17 '11 at 03:59
What @Mechanical Snail said, Kit, you may want to brush up on what file system metadata is and how file systems actually work, the reason you cannot "rename to" across partitions is simple, the rename operation actually only changes the file metadata on the file system in question, it does not actually move any data. And since the /mnt doesnt actually contain the data yet, simply updating some metadata flags to point to a name would be pointless, there is no data for the name to point to. Thats why you always have to move(or copy) across partitions. — user439407, Aug 17 '11 at 05:00
Moving the file of course, there is no one line way to do it in Java, this method looks pretty good http://stackoverflow.com/questions/300559/move-copy-file-operations-in-java — user439407, Aug 17 '11 at 06:19

score 7 · Answer 1 · answered Aug 17 '11 at 03:55

7

You can't do a rename across file systems (partitions).

answered Aug 17 '11 at 03:55

jdigital

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1

@Kit Ho: you have to copy everything to /mnt and then delete original files. – Denis Tulskiy Aug 17 '11 at 03:58

jirka.pinkas · Accepted Answer · 2011-08-24T21:02:57.880

4

Create a method to copy file and call this method (that's what I use when renameTo() doesn't work):

void copyFile(File source, File destination) throws Exception {
  FileInputStream inputStream = new FileInputStream(source);
  FileOutputStream outputStream = new FileOutputStream(destination);
  int b = -1;
  while ((b = inputStream.read()) != -1) {
    outputStream.write(b);
  }
  inputStream.close();
  outputStream.close();
}

edit: if you want to move file, delete original after making a copy.

edit: even better would be FileUtils.moveFile() from Apache Commons library

edited Aug 24 '11 at 21:02

answered Aug 17 '11 at 06:18

jirka.pinkas

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`moveFile()` is the best way. The presented implementation is buggy (does not properly close streams) and inefficient (reads single bytes). If these things were left off for brevity, it should've been noted. – musiKk Aug 25 '11 at 09:29
sorry. I should have noted, that this is simplified for brevity. – jirka.pinkas Aug 27 '11 at 07:44

score 3 · Answer 3 · edited Aug 28 '14 at 11:33

3

A simple 'don't reinvent the wheel' solution would be to use Apache Commons IO. It has FileUtils#moveFile() that takes care of handling different partitions.

edited Aug 28 '14 at 11:33

Sbl

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6

answered Aug 17 '11 at 09:34

musiKk

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score 1 · Answer 4 · answered Aug 17 '11 at 03:59

File.renameTo may fail if you're moving across file systems, or if you're trying to overwrite an existing file. See the docs.

You also may have a problem since /mnt is a special purpose location and may have other attributes that prevent you from moving something into /mnt.

How to rename a file to another file system?

4 Answers4