SAO TDC ASCII Parameters
When a program with numerous parameters, such as
skymap,
rgsc, or
star,
is used frequently, it soon becomes
desirable to save values between executions of the program. I have designed
and implemented a system of subroutines and utilities to make this task easy
for both programmers and users. The fastest way to save values is to store the
parameters in a Fortran common or C data structure and write the whole
structure to disk in one output operation, later retrieving it in one input
operation. While this technique is fast, it is not easily extensible when new
parameters are added to a program, and the parameter files are not portatble
between computers of different architecture. Every subroutine which uses the
structure must be recompiled when any change is made. In addition, the binary
parameter file cannot easily be read outside the program which uses it.
A simple ASCII parameter file format has been designed based on the FITS image
file header, and software has been created to utilize it. skymap uses the
IOLIB library which contains subroutines to read from and write to an ASCII
parameter string, using only the name of the parameter, a variable to contain
the binary value, and a data type flag.
The parameter file structure is clear enough that such a file can be edited by
an ASCII file editor such as vi or emacs. Either the command-line features of
skymap described below or stand-alone programs can be used to read or modify
the parameter files. Values can be changed or checked on the command line,
allowing the the Unix shell to be used in a way similar to the IRAF Command
Language for batch operation of programs. Although this is a fairly
rudimentary system, it has been in use for several years and is fairly well
debugged.
- Parameter Format
- Reading and
Writing Parameter Files
- Using Parameter Files