Grepping a file for a specific pattern

Question

          I'm trying to use a servlet to mimic a tail/grep operation on a log file. Whilst
          I can use a FileReader
          to get the contents of a file and put them to a string and display on a browser,
          I am only interested in a certain pattern.
          E.g. on my Unix web server if I type the command
          $tail -f mylog | grep 'ERROR'
          It returns only strings that contain an error message.
          I tried looking at java.util.StringTokenizer and java.io.StreamTokenizer but they
          both
          seem quite limited.
          Obviously tailing might be a bit tricky, but it would be great to find a way to
          search througha file for
          error information.
          thanks
          Mark
          

Answer 1

I use something like the following to go through a log file for particular
          application errors...
          Thanks
          Rob
          RandomAccessFile fis = new
          RandomAccessFile("mylog.log","r");
          long fpointer = 0;
          long flength = fis.length();
          out.println("the log file is " + flength + "
          bytes.");
          while( fpointer < flength ) {
          String s = fis.readLine();
          if(s.indexOf("ERROR") == -1)
          continue;
          "Mark McKee" <[email protected]> wrote in message
          news:3adf14db$[email protected]..
          >
          > I'm trying to use a servlet to mimic a tail/grep operation on a log file.
          Whilst
          > I can use a FileReader
          > to get the contents of a file and put them to a string and display on a
          browser,
          >
          > I am only interested in a certain pattern.
          >
          > E.g. on my Unix web server if I type the command
          >
          > $tail -f mylog | grep 'ERROR'
          >
          > It returns only strings that contain an error message.
          >
          > I tried looking at java.util.StringTokenizer and java.io.StreamTokenizer
          but they
          > both
          > seem quite limited.
          >
          > Obviously tailing might be a bit tricky, but it would be great to find a
          way to
          > search througha file for
          > error information.
          >
          > thanks
          > Mark