private static int determineLineEndingLength(final byte[] bytes) {
        if (bytes.length > 0) {
            switch (bytes[bytes.length - 1]) {
                case '\r':
                    return 1;
                case '\n':
                    return ((bytes.length > 1) && (bytes[bytes.length - 2] == '\r')) ? 2 : 1;
            }
        }
        return 0;
    }
Holds exactly one complete line of container output. Lines are split on newline characters (LF, CR LF).
core/src/main/java/org/testcontainers/containers/output/OutputFrame.java