Java RandomAccessFile.java under linux not working correctly -

im trying implement simple tail -f linux command in java. here code.

try     {         // position within file         file file = new file("/home/curuk/monitored/log.txt");         randomaccessfile rafile = new randomaccessfile(file, "r");         long last = file.lastmodified(); // last time file checked changes         long position = file.length();         while (true)         {             if (file.lastmodified() > last)             {                 last = file.lastmodified();                 readfromfile(rafile, (int) position, (int) (file.length() - position));                 position = file.length();             }             thread.sleep(1000);         }     }     catch (ioexception e)     {         e.printstacktrace();     }  private byte[] readfromfile(randomaccessfile file, int position, int size) throws ioexception     {         file.seek(position);         byte[] bytes = new byte[size];         system.err.println(file.read(bytes, 0, size));         string s = new string(bytes);         system.err.println(s);         return bytes;     } 

the problem under linux os, file.read(bytes, 0, size) returns -1, while under windows same snippet of code works fine (always prints new line).

edit:

i solved problem adding rafile = new randomaccessfile(file, "r"); @ every iteration.

while (true)             {                 rafile = new randomaccessfile(file, "r");                 if (file.lastmodified() > last)                 {                     last = file.lastmodified();                     readfromfile(rafile, (int) position, (int) (file.length() - position));                     position = file.length();                 }                 thread.sleep(1000);             } 

don't know why, works fine under linux well. effort guys

here solution entirely based on java 7, using new watchservice infrastructure:

works, quite crude...

public final class baz {     public static void main(final string... args)         throws ioexception     {         // paths containing directory , file want spy         final path dir = paths.get("/tmp");         final path file = dir.resolve("foo.txt");          // watch service our default filesystem         // interested in modifications , deletions         final watchservice service = filesystems.getdefault().newwatchservice();         dir.register(service, standardwatcheventkinds.entry_modify,             standardwatcheventkinds.entry_delete);          // charset decoder -- reading bytes file,         // need decode them string         final charsetdecoder decoder = standardcharsets.utf_8.newdecoder()             .onmalformedinput(codingerroraction.ignore)             .onunmappablecharacter(codingerroraction.ignore);           try (             // open seekablebytechannel file -- read             final seekablebytechannel channel                 = files.newbytechannel(file, standardopenoption.read);         ) {             long oldsize;             while (true) {                 // current size of our file                 oldsize = channel.size();                 try {                     // grab key                     final watchkey key = service.poll(1l, timeunit.seconds);                     if (key == null) // no events...                         continue;                      (final watchevent<?> e: key.pollevents()) {                         @suppresswarnings("unchecked")                         final watchevent<path> event = (watchevent<path>) e;                          // kind of event, whom applies                         final watchevent.kind<path> kind = event.kind();                         final path context = dir.resolve(event.context());                          // if not us, don't care                         if (!context.equals(file))                             continue;                          // if our file has disappeared, exit                         if (kind == standardwatcheventkinds.entry_delete) {                             system.err.println("file deleted");                             system.exit(0);                         }                          // ok, it's modification, , our file: read tail                         doread(oldsize, decoder, channel);                     }                     // reset key next batch of events                     key.reset();                 } catch (interruptedexception e) {                     // service.poll() interrupted: out                     break;                 }             }         }     }      private static void doread(final long oldsize, final charsetdecoder decoder,         final seekablebytechannel channel)         throws ioexception     {         final long newsize = channel.size();         if (newsize <= oldsize)             return;         final int bufsize = (int) (newsize - oldsize);         final bytebuffer buf = bytebuffer.allocate(bufsize);         channel.position(oldsize).read(buf);         buf.rewind();         decoder.reset();         system.out.println(decoder.decode(buf).tostring());     } }