Consuming an increasing file with Java

User_4MPMN

Hi all,

I have to write a java program which have to parse an Apache log. As the Apache log grows continuously throughout the day I would like the java program listens continuously any new record in the log so I can parse it at real time. (I don't want to start to parse the log everytime from the beginning).

Any suggestions ?

Thanks in advance

Lele

Roland Mueller

Hello,

here is some simple static method that behaves like Linux/Unix 'tail -f <some_filename>'.

Sleep period is hardcoded to 3000ms and the payload i.e. what the method is doing with the file content is simply println() to stdout.

BR,

Roland

 12     public static void tail(String fname)
 13         throws InterruptedException, IOException, FileNotFoundException, InterruptedException
 14     {
 15         RandomAccessFile f = new RandomAccessFile( fname, "r" );
 16         long posInFile = 0;
 17 
 18         while (true) {
 19             long fileLength = f.length();
 20             if (fileLength > posInFile) {
 21                 f.seek(posInFile);
 22                 String line = f.readLine();
 23                 while( line != null ) {
 24                     System.out.println(line); // payload //
 25                     line = f.readLine();
 26                 }
 27                 posInFile = f.getFilePointer();
 28             }
 29 
 30             Thread.sleep(3000);
 31         }
 32     }

User_4MPMN

Hi Roland, thanks for your suggestion.

I'll try it

Gabriele