commonlib/src/main/java/com/streamsets/pipeline/lib/io/SingleLineLiveFileReader.java
@Override
  public long getOffset() {
    Utils.checkState(open, Utils.formatL("LiveFileReder for '{}' is not open", currentFile));
    return (truncateMode) ? -offset : offset;
  }
@Override
  public long getOffset() {
    Utils.checkState(open, Utils.formatL("LiveFileReder for '{}' is not open", currentFile));
    return (truncateMode) ? -offset : offset;
  }
offset will be negative if we are in truncate mode.