org.unix4j.unix.tail.TailOptions Maven / Gradle / Ivy
package org.unix4j.unix.tail;
import java.util.Collections;
import java.util.Iterator;
import org.unix4j.convert.OptionSetConverters.OptionSetConverter;
import org.unix4j.convert.ValueConverter;
import org.unix4j.option.DefaultOptionSet;
import org.unix4j.option.Option;
import org.unix4j.option.OptionSet;
import org.unix4j.unix.Tail;
import org.unix4j.unix.tail.TailOption;
/**
* Interface implemented by all option sets for the {@link Tail tail} command.
* It is recommended to use {@link Tail#Options} to specify a valid
* combination of options.
*
* The options for the tail command are:
*
*
* {@code -c} {@code --chars} The {@code count} argument is in units of characters instead of
lines. Starts from 1 and includes line ending characters. {@code -q} {@code --suppressHeaders} Suppresses printing of headers when multiple files are being
examined. {@code -s} {@code --countFromStart} The {@code count} argument is relative to the beginning of the file
instead of counting from the end of the file. For instance,
{@code tail -s 10} prints the lines starting from line 10;
{@code tail -s 1} prints the whole file.
*
* This interface serves as an alias for the extended interface to simplify the
* command signature methods by avoiding generic parameters.
*/
public interface TailOptions extends OptionSet {
/**
* Constant for an empty option set.
*/
TailOptions EMPTY = new TailOptions() {
@Override
public Class optionType() {
return TailOption.class;
}
@Override
public boolean isSet(TailOption option) {
return false;
}
/**
* Returns 0 as this is a set with no active options.
*
* @return zero
*/
@Override
public int size() {
return 0;
}
/**
* Returns an immutable empty set.
*
* @return an immutable empty set.
*/
@Override
public java.util.Set asSet() {
return Collections.emptySet();
}
/**
* Returns an iterator returning no elements.
*
* @return an immutable iterator with no elements.
*/
@Override
public Iterator iterator() {
return asSet().iterator();
}
/**
* Returns true if the {@link Option#acronym() acronym} should be used
* for the specified {@code option} in string representations.
*
* This method returns always true;
*
* @param option
* the option of interest
* @return always true
*/
@Override
public boolean useAcronymFor(TailOption option) {
return true;
}
};
/**
* Default implementation for a modifiable option set.
*/
class Default extends DefaultOptionSet implements TailOptions {
/**
* Default constructor for an empty option set with no active options.
*/
public Default() {
super(TailOption.class);
}
/**
* Constructor for an option set with a single active option.
* @param option the option to be set
*/
public Default(TailOption option) {
super(option);
}
/**
* Constructor for an option set with the given active options.
* @param options the options to be set
*/
public Default(TailOption... options) {
this();
setAll(options);
}
/**
* Constructor for an option set initialized with the options given by
* another option set.
*
* @param optionSet set with the options to be active
*/
public Default(OptionSet optionSet) {
this();
setAll(optionSet);
}
}
/**
* Value converter for {@link TailOptions} based on an {@link OptionSetConverter}.
*/
ValueConverter CONVERTER = new ValueConverter() {
private final OptionSetConverter converter = new OptionSetConverter(TailOption.class);
@Override
public TailOptions convert(Object value) {
final OptionSet set = converter.convert(value);
return set == null ? null : new Default(set);
}
};
}