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Kiwi is a utility library. We really like Google's Guava, and also use Apache Commons. But if they don't have something we need, and we think it is useful, this is where we put it.

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package org.kiwiproject.base.process;

import static java.util.Objects.requireNonNull;

/**
 * A few common (Unix/Linux/etc) kill signals.
 */
@SuppressWarnings("unused")
public enum KillSignal {

    /**
     * Hang up signal, e.g. {@code kill -1}
     */
    SIGHUP(1),

    /**
     * Interrupt signal, e.g. {@code kill -2}
     */
    SIGINT(2),

    /**
     * Quit signal, e.g. {@code kill -3}
     */
    SIGQUIT(3),

    /**
     * Non-catchable, non-ignorable kill signal, e.g. {@code kill -9}
     */
    SIGKILL(9),

    /**
     * Software termination signal, e.g. {@code kill -15}
     */
    SIGTERM(15);

    private static final char DASH = '-';

    public final int signalNumber;

    KillSignal(int number) {
        this.signalNumber = number;
    }

    /**
     * @return the number associated with this signal.
     */
    public String number() {
        return String.valueOf(signalNumber);
    }

    /**
     * Given a signal, prepend a leading dash if necessary, e.g. change "9" into "-9".
     *
     * @param signal the signal to modify
     * @return the possibly modified signal with a leading dash
     */
    public static String withLeadingDash(String signal) {
        requireNonNull(signal);
        if (signal.charAt(0) == DASH) {
            return signal;
        }
        return DASH + signal;
    }

    /**
     * Return this signal's number with a leading dash, e.g. "-3".
     *
     * @return this instance of signal's number with a leading dash
     */
    public String withLeadingDash() {
        return withLeadingDash(this.number());
    }

}