3.4 Your  history files

Every uv and image file has an associated “history”, or HI, file. This HI “extension” of the data set stores important information about the processing done so far on the data in the file. Every  task and verb that alters either the data or the file header will record its key parameters in the history file. The history file is written to the disk file when you use FITS format, so you can preserve it for reference in later  sessions or when sending data to colleagues.

In general, each “card” in the history file begins with the task or verb name. It then gives one or more of the input adverb values it used (i.e., the defaults are filled in). All or parts of the file may be displayed on your terminal or printed on the line printer. For example, use:

There are several (legitimate) reasons why you might wish to edit your history files. Repetitive self-calibration cycles, or image combinations, can lead to very long and very repetitive histories which could be substantially shortened with no real loss of information. Also some entries in the history file may become obsolete by, say, the deletion of plot files. The verb STALIN allows you to send a range of history lines to Siberian salt mines (i.e., delete) by number with optional selection by task and, optionally, interactive confirmation of each deletion. You may, of course, simply wish to add information to the history file. The verb HINOTE can be used to append one line, given by the adverb COMMENT, or many lines, typed in interactively, to the history file. Even more powerfully, the verb HITEXT allows you to write your history file to an external text file (see §3.10.1). You may edit that file with your favorite Unix file editor and then read it back, writing your edited file into any  history file you want (with verb HINOTE).