In the UNIX/Linux environment, the first Acquire file to be captured is a ps file with an odd numbered extension. The presence of this odd-numbered file indicates the start of a measurement period. The next set of captured files have an even extension number 1 higher than this, and from then on the extension numbers are always even. Since the maximum length of a measurement period is one week, there will be an odd-numbered ps file at least once every seven days.