File.lengh() return 0 while the file's length > 0 on Linux

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2 total messages Started by Chris Thu, 17 Mar 2005 07:02

#61

Author: Chris
Date: Thu, 17 Mar 2005 07:02

17 lines
1401 bytes

Howdy, 

When using File.length to get the size of a file on linux, it returns 0;
but I am sure the file has contents, Could someone give me a hint?

Thanks in advance .

//test.java
import java.io.*;
public class test
{
       public static void main(String args[])
       {
               File file = new File("/proc/mdstat");
               System.out.println("file.length(): " + file.length());
       }
}

Re: File.lengh() return 0 while the file's length > 0 on Linux

#62

Author: Kevin Dean [TeamB]
Date: Thu, 17 Mar 2005 16:28

39 lines
2297 bytes

Chris wrote:

> When using File.length to get the size of a file on linux, it returns
> 0; but I am sure the file has contents, Could someone give me a hint?
> 
> Thanks in advance .
> 
> //test.java
> import java.io.*;
> public class test
> {
>        public static void main(String args[])
>        {
>                File file = new File("/proc/mdstat");
>                System.out.println("file.length(): " + file.length());
>        }
> }

The /proc filesystem is a special file system that maintains process
state.  The contents don't exist on disk but rather in memory, and the
contents are highly dynamic.  Because you're not opening a real file
per se, there's no easy way to determine the length, so Java returns 0.

Details on /proc can be found here:

http://www.freeos.com/articles/2879/

-- 
Kevin Dean [TeamB]
Dolphin Data Development Ltd.
http://www.datadevelopment.com/

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