org.unix4j.command

Interface CommandInterface<R>

Type Parameters:

R - the return type for all command signature methods, usually a new command instance or a command fromFile providing methods for chained invocation of following commands

All Known Subinterfaces:

Cat.Interface<R>, Cd.Interface<R>, Cut.Interface<R>, Echo.Interface<R>, Find.Interface<R>, From.Interface<R>, Grep.Interface<R>, Head.Interface<R>, Ls.Interface<R>, Sed.Interface<R>, Sort.Interface<R>, Tail.Interface<R>, Uniq.Interface<R>, Unix4jCommandBuilder, Wc.Interface<R>, Xargs.Interface<R>

All Known Implementing Classes:

CatFactory, CdFactory, CutFactory, DefaultUnix4jCommandBuilder, EchoFactory, FindFactory, FromFactory, GrepFactory, HeadFactory, LsFactory, SedFactory, SortFactory, TailFactory, UniqFactory, WcFactory, XargsFactory

public interface CommandInterface<R>

A command interface defines the different ways a certain Command can be invoked (or instantiated). It consists of the different method signatures for the command.

Consider for instance the following simplified ls command. It can be called without options, with a file, with option flags or both a file and options. The command interface for ls would therefore define four methods:

 R ls()
 R ls(File file)
 R ls(Ls.Option... options)
 R ls(File file, Ls.Option... options)
 

Note that all command methods in the interface usually return the generic type R. Command factories (see Factory constant of a specific command} return a new command instance. Command builders implementing many different command interfaces return an instance to itself (the BUILDER) to allow for method chaining, for instance when creating a joined command.

This interface does not define any methods since all methods are defined by the concrete command. The interface serves as a marker and documentation interface. Theoretically, a command interface is not required to extend this interface, but it is highly recommended. Also, if a command factory is used with GenericCommandBuilder, it must implement this interface.