Most commands that query data use the same syntax. Without argument, the command lists the datafile; with one argument, it returns the star data if the argument is numeric or execute the appropriate option. To make a selection, enter the command followed by the parameter name on which the selection is made, the comparator and the value:
command parameter comparator value
The definition of the parameters for each datafile is given in Appendix E. It may be obtained simply with the command field described above. The discussion of the command ubv will illustrate this syntax, which is the same for all selections.