    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      https://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.lang3;
    019
    020import java.io.IOException;
    021import java.nio.charset.Charset;
    022import java.nio.file.Files;
    023import java.nio.file.Paths;
    024import java.util.Arrays;
    025
    026/**
    027 * Helps query the runtime environment.
    028 *
    029 * @since 3.15.0
    030 */
    031public class RuntimeEnvironment {
    032
    033    private static boolean fileExists(final String path) {
    034        return Files.exists(Paths.get(path));
    035    }
    036
    037    /**
    038     * Tests whether we are running in a container like Docker or Podman.
    039     *
    040     * @return whether we are running in a container like Docker or Podman. Never null
    041     */
    042    public static Boolean inContainer() {
    043        return inContainer(StringUtils.EMPTY);
    044    }
    045
    046    static boolean inContainer(final String dirPrefix) {
    047        /*
    048        Roughly follow the logic in SystemD:
    049        https://github.com/systemd/systemd/blob/0747e3b60eb4496ee122066c844210ce818d76d9/src/basic/virt.c#L692
    050
    051        We check the `container` environment variable of process 1:
    052        If the variable is empty, we return false. This includes the case, where the container developer wants to hide the fact that the application runs in a container.
    053        If the variable is not empty, we return true.
    054        If the variable is absent, we continue.
    055
    056        We check files in the container. According to SystemD:
    057        /.dockerenv is used by Docker.
    058        /run/.containerenv is used by PodMan.
    059
    060         */
    061        final String value = readFile(dirPrefix + "/proc/1/environ", "container");
    062        if (value != null) {
    063            return !value.isEmpty();
    064        }
    065        return fileExists(dirPrefix + "/.dockerenv") || fileExists(dirPrefix + "/run/.containerenv");
    066    }
    067
    068    /**
    069     * Tests whether the {@code /proc/N/environ} file at the given path string contains a specific line prefix.
    070     *
    071     * @param envVarFile The path to a /proc/N/environ file.
    072     * @param key        The env var key to find.
    073     * @return value The env var value or null.
    074     */
    075    private static String readFile(final String envVarFile, final String key) {
    076        try {
    077            final byte[] bytes = Files.readAllBytes(Paths.get(envVarFile));
    078            final String content = new String(bytes, Charset.defaultCharset());
    079            // Split by null byte character
    080            final String[] lines = content.split(String.valueOf(CharUtils.NUL));
    081            final String prefix = key + "=";
    082            return Arrays.stream(lines)
    083                    .filter(line -> line.startsWith(prefix))
    084                    .map(line -> line.split("=", 2))
    085                    .map(keyValue -> keyValue[1])
    086                    .findFirst()
    087                    .orElse(null);
    088        } catch (final IOException e) {
    089            return null;
    090        }
    091    }
    092
    093    /**
    094     * Constructs a new instance.
    095     *
    096     * @deprecated Will be removed in 4.0.0.
    097     */
    098    @Deprecated
    099    public RuntimeEnvironment() {
    100        // empty
    101    }
    102}