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2.3 Task Arguments

The <task-args> part of the command line is a list of parameter assignments, each giving the value of one of the named parameters belonging to the task which is specified in the <task-name> part.

The general form of each parameter assignment is

   <param-name>=<param-value>
If you want to set the parameter to the null value, which is legal for some but not all parameters, use the special string "null". In some cases you can optionally leave out the <param-name> part of the assignment (i.e. the parameter is positionally determined); this is indicated in the task's usage description if the parameter is described like [<param-name>=]<param-value> rather than <param-name>=<param-value>. If the <param-value> contains spaces or other special characters, then in most cases, such as from the Unix shell, you will have to quote it somehow. How this is done depends on your platform, but usually surrounding the whole value in single quotes will do the trick.

Tasks may have many parameters, and you don't have to set all of them explicitly on the comand line. For a parameter which you don't set, two things can happen. In many cases, it will default to some sensible value. Sometimes however, you may be prompted for the value to use. In the latter case, a line like this will be written to the terminal:

   matcher - Name of matching algorithm [sky]:
This is prompting you for the value of the parameter named matcher. "Name of matching algorithm" is a short description of what that parameter does. "sky" is the default value (if there is no default, no value will appear in square brackets). At this point you can do one of four things: Under normal circumstances, most parameters which have a legal default value will default to it if they are not set on the command line, and you will only be prompted for those where there is no default or the program thinks there's a good chance you might not want to use it. You can influence this however using flags to the stilts command itself (see Section 2.1). If you supply the -prompt flag, then you will be prompted for every parameter you have not explicitly set. If you supply -batch on the other hand, you won't be prompted for any parameters (and if you fail to set any without legal default values, the task will fail).

If you want to see the actual values of the parameters for a task as it runs, including prompted values and defaulted ones which you haven't specified explicitly, you can use the -verbose flag after the stilts command:

   % stilts -verbose tcopy cat.fits cat.vot ifmt=fits
   INFO: tcopy in=cat.fits out=cat.vot ifmt=fits ofmt=(auto)

Extensive help is available from stilts itself about task and its parameters, as described in the next section.


Next Previous Up Contents
Next: Getting Help
Up: The stilts command
Previous: Task Names

STILTS - Starlink Tables Infrastructure Library Tool Set
Starlink User Note256
STILTS web page: http://www.starlink.ac.uk/stilts/
Author email: m.b.taylor@bristol.ac.uk