Locates program name using the
target package context and returns the fully resolved filename.
name must be a string that specifies the
filename or path to an external program.
The program is searched for using the
external program search order.
Returns .nil if name cannot be located.
Example 5.42. Package class — findProgram method
say.context~package~findProgram("mime.cls")-- e. g. C:\Program Files\ooRexx\mime.cls
