The whole parameters set used in a graphic session and the task's messages are written in the file DIRALOG.OLD (DIRALOG.LOG if the session is ended in an abnormal way) in the user current directory. This is an ASCII file of variable length records that the user can save to obtain a permanent log of the operations executed during the graphic session. Remember that only a version of this file is keep. When you want to save a log file you must rename this before to start an other graphic command.
A typical log file is the following :
CATalogue UGC RA 100000 110000 DEClination 200000 300000 CONstraints MAG < 15 BREak REM> field Abell 10 REMark no. 69 Objects found SYMbol 2 3 4 5 6 7 1 1 COLor 2 3 2 3 2 3 2 3 CATalogue ABELL REMark no . 14 Objects found REM> overlay 23K5
Where each record is a verb or a note coming from the task or from a direct 'REMark' command entered by the user.
One of the main features of the graphic session of DIRA is that you can reload this log file to obtain all the catalogues opened and the parameters redefined in a successive task. Since the log file is an ASCII sequential file, you can modify or create the file, using an editor, to prepare a future graphic session.
The log file is then a tool to exchange data between tasks, then a graphic task can load the file created by another one. For example, you can select a sky region using the DB_CHART task, then you can load the log file in DB_WEDGE task to get a wedge diagram, then you can load the file again in a DB_HISTO to get an histogram of the objects displayed with the wedge diagram.
When, during the execution of a 'LOAd' command (that loads and reads a log file), a verb is not followed by a valid parameter(s) the loading is interrupted and a prompt string is typed on the terminal; you must type a valid parameter value, then the load is resumed. If you need a structure that prompts for a defined sequence of parameters you can create a file in which only the verbs are present. When you load it you can get a sequence of questions.
The commands for the management of the log file are:
|LOAd||Loads an existing log file|
|NEXt||Continues the load of the log file after a break|
|SAVe||Saves the current log with a user defined name|
|BREak||Sets a break mark on the log file|
|REMark||Writes a string in the log file|
|DELete||Clears a log file|