Like any Starlink program
EXTRACTOR may be run from the Unix shell or from a user-interface
such as ICL (see SG/5). A useful summary of the rich variety of methods of specifying
parameter values is given in SUN/95. C-shell users should also consult SC/4, the C-Shell
The examples below assume you are running from the Unix shell but the commands and parameters are exactly the same from ICL.
After normal Starlink startup, at the shell prompt, type:
to initialise the package and then:
to run the program. You will now be prompted for the values of parameters CONFIG and IMAGE in turn:
where CONFIG is the name of the ‘preferences’ file and IMAGE is the name of the image file to be processed.
Suggested values are given between
// in the prompt. You can accept the suggested values by just
typing <RETURN>. If you accept the suggested values shown above,
EXTRACTOR will process the NDF
"image" using the installed default configuration files to produce a catalogue named
name is specified in the preferences file).
CONFIG has a ‘default’ value of
$EXTRACTOR_DIR/config/default.sex. This file has some sensible
defaults but you will probably want to copy it to your own directories and modify it to your taste (as
you would for the native
SExtractor program). Similarly with the other configuration files. The
EXTRACTOR_DIR is defined to point to the directory containing the
EXTRACTOR program and the
You can also provide parameter values on the command line. Either positionally,
or by keyword,
(In this case, you would be prompted for IMAGE but not for CONFIG.)
The additional parameters KEYWORDS, NAME and VALUE allow configuration parameters specified in the preferences file to be overridden without editing the file. For example:
would change the name and type of the catalogue produced (for this run only). The list of changes is
terminated by replying with the NULL response (
!) to the prompt. The
SExtractor User’s Guide
(MUD/165) gives a full list of possible parameter names and values, but it is only sensible to change a
few in this way.
If you’d like to run
EXTRACTOR from a script, just say for instance sampling different populations of
objects at different thresholds, you can do this using the NAME VALUE parameters (avoiding the
need to have multiple configuration files), but you need to adopt a slightly different strategy to normal
programs. Here’s one example script:
Example batch script
Using the C-shell <<EOF mechanism allows you to send information to the program as if you’re typing it in.