这是“文件格式探究”专题的第 1 期——初探 “ePub” 文件格式。这个专题将会给各位读者呈现笔者探索各种文件格式的过程，具体则是文件的内容是如何呈现出来的。原则上我们假定仅对于这些文件格式的用途有所了解，但具体实现的细节并不清楚 (如果提前掌握了部分内容，笔者全当其不存在) 。探究过程中我们会尝试使用各种方法来逐渐初步掌握其概貌。
根据维基百科大陆简体版本的相关描述：
EPub 是一个自由的开放标准，属于一种可以“自动重新排版”的内容；也就是文字内容可以根据阅读设备的特性，以最适于阅读的方式显示。
之所以后面不截是因为再截就剧透了。简单来说，ePub 就是类似于 PDF 那样的“文档型”文件格式，常用于分发电子读物等。
现在笔者手头上有一份用于测试的 ePub 文件，文件路径为 ~/Downloads/咖啡馆推理事件簿系列（全四本）.epub (趁机夹带私货，反正很合我胃口就是了) ，后续所有的探究活动均建立于此文件上。笔者目前的操作系统环境为 Manjaro 21.1.0 on amd64，终端环境为 GNU bash 5.1.8(1)-release 。为了方便，我们先把文件改个名字 (那你还把原来的名字给出来干嘛？！) ：
[littleye233@lymjrolt Downloads]$ cd ~
[littleye233@lymjrolt ~]$ cd Downloads
[littleye233@lymjrolt Downloads]$ mv 咖啡馆推理事件簿系列（全四本）.epub test.epub
[littleye233@lymjrolt Downloads]$ ll test.epub
-rw-r--r-- 1 littleye233 littleye233 1253964 Aug 22 23:24 test.epub
首先我们先尝试用 Linux 系统的内置命令 file 试试水，看看会输出什么东西。键入 file test.epub后执行：
[littleye233@lymjrolt Downloads]$ file test.epub
test.epub: EPUB document EPUB document
哎呀，真可惜！ file 命令几乎什么有效信息都没给我们。 file 命令的 man 页面明确给出此命令可以判断文件格式，但其实它能做到的有很多，例如如果对一个图片文件使用 file ，可能会出现类似下面的结果：
[littleye233@lymjrolt Downloads]$ file ~/.local/share/osu/screenshots/osu_2021-08-21_23-40-03.png
/home/littleye233/.local/share/osu/screenshots/osu_2021-08-21_23-40-03.png: PNG image data, 1920 x 961, 8-bit/color RGBA, non-interlaced
这样我们可以通过 file 中提供的相关信息顺藤摸瓜，尝试在文件的二进制编码内容中寻找其蛛丝马迹，进而推测对应“位点”所表达的含义 (因为一些文件格式要求在特定的位置表达某些含义) ，如果能提供类似注释的信息就再好不过了。
现在我们回到这个 ePub 文件上来。现在我们尝试能否直接获取其内容，目的是通过文件头部的部分可见字符猜测其文件结构。输入 nano test.epub 直接预览，或使用 head --bytes=120 test.epub 查看前面 120 个字节的内容：
[littleye233@lymjrolt Downloads]$ head --bytes=120 test.epub
PK!oa?mimetypeapplication/epub+zipPU?N?;???META-INF/container.xml]?A
?0E?=
果不其然，我们看到了一些有趣的字眼： “mimetypeapplication/epub+zip” ，凭经验猜测，这应该是 ePub 文件格式的文件头，而其中的 “zip” 也说明—— ePub 文件可能本质上就是一个压缩档。
其实很多文件格式 (例如 Word 文档 “*.docx”) 其本质都是在一个压缩档中加入各种资源文件和配置文件，只要有对应的软件进行读取并重新加工，用户即能看到效果。
现在我们可以使用解压缩程序解出 ePub 文件中的内容了。在终端中执行 unzip -l test.epub ：
[littleye233@lymjrolt Downloads]$ unzip -l test.epub
Archive: test.epub
Length Date Time Name
--------- ---------- ----- ----
20 1980-01-01 00:00 mimetype
251 2019-06-27 10:40 META-INF/container.xml
12307 2019-06-27 10:40 OEBPS/content.opf
112368 2019-06-27 10:40 OEBPS/Images/cover00464.jpeg
128680 2019-06-27 10:40 OEBPS/Images/image00456.jpeg
120936 2019-06-27 10:40 OEBPS/Images/image00457.jpeg
1392 2019-06-27 10:40 OEBPS/Images/image00458.jpeg
101948 2019-06-27 10:40 OEBPS/Images/image00459.jpeg
119124 2019-06-27 10:40 OEBPS/Images/image00460.jpeg
1268 2019-06-27 10:40 OEBPS/Images/image00461.jpeg
42944 2019-06-27 10:40 OEBPS/Images/image00462.jpeg
121284 2019-06-27 10:40 OEBPS/Images/image00463.jpeg
2251 2019-06-27 10:40 OEBPS/Styles/style0001.css
9816 2019-06-27 10:40 OEBPS/Styles/style0002.css
2251 2019-06-27 10:40 OEBPS/Styles/style0003.css
9789 2019-06-27 10:40 OEBPS/Styles/style0004.css
2251 2019-06-27 10:40 OEBPS/Styles/style0005.css
29245 2019-06-27 10:40 OEBPS/Styles/style0006.css
2235 2019-06-27 10:40 OEBPS/Styles/style0007.css
29914 2019-06-27 10:40 OEBPS/Styles/style0008.css
2251 2019-06-27 10:40 OEBPS/Styles/style0009.css
624 2019-06-27 10:40 OEBPS/Text/cover_page.xhtml
851 2019-06-27 10:40 OEBPS/Text/part0000.xhtml
561 2019-06-27 10:40 OEBPS/Text/part0001.xhtml
428 2019-06-27 10:40 OEBPS/Text/part0002.xhtml
1518 2019-06-27 10:40 OEBPS/Text/part0003.xhtml
661 2019-06-27 10:40 OEBPS/Text/part0004.xhtml
2311 2019-06-27 10:40 OEBPS/Text/part0005.xhtml
55157 2019-06-27 10:40 OEBPS/Text/part0006.xhtml
58266 2019-06-27 10:40 OEBPS/Text/part0007.xhtml
59953 2019-06-27 10:40 OEBPS/Text/part0008.xhtml
49789 2019-06-27 10:40 OEBPS/Text/part0009.xhtml
66870 2019-06-27 10:40 OEBPS/Text/part0010.xhtml
57342 2019-06-27 10:40 OEBPS/Text/part0011.xhtml
67449 2019-06-27 10:40 OEBPS/Text/part0012.xhtml
16183 2019-06-27 10:40 OEBPS/Text/part0013.xhtml
561 2019-06-27 10:40 OEBPS/Text/part0014.xhtml
428 2019-06-27 10:40 OEBPS/Text/part0015.xhtml
1575 2019-06-27 10:40 OEBPS/Text/part0016.xhtml
496 2019-06-27 10:40 OEBPS/Text/part0017.xhtml
1446 2019-06-27 10:40 OEBPS/Text/part0018.xhtml
52358 2019-06-27 10:40 OEBPS/Text/part0019.xhtml
75746 2019-06-27 10:40 OEBPS/Text/part0020.xhtml
63420 2019-06-27 10:40 OEBPS/Text/part0021.xhtml
57399 2019-06-27 10:40 OEBPS/Text/part0022.xhtml
58590 2019-06-27 10:40 OEBPS/Text/part0023.xhtml
40263 2019-06-27 10:40 OEBPS/Text/part0024.xhtml
66099 2019-06-27 10:40 OEBPS/Text/part0025.xhtml
15143 2019-06-27 10:40 OEBPS/Text/part0026.xhtml
561 2019-06-27 10:40 OEBPS/Text/part0027.xhtml
612 2019-06-27 10:40 OEBPS/Text/part0028.xhtml
1344 2019-06-27 10:40 OEBPS/Text/part0029.xhtml
640 2019-06-27 10:40 OEBPS/Text/part0030.xhtml
6144 2019-06-27 10:40 OEBPS/Text/part0031.xhtml
25197 2019-06-27 10:40 OEBPS/Text/part0032.xhtml
54594 2019-06-27 10:40 OEBPS/Text/part0033.xhtml
87394 2019-06-27 10:40 OEBPS/Text/part0034.xhtml
97557 2019-06-27 10:40 OEBPS/Text/part0035.xhtml
109901 2019-06-27 10:40 OEBPS/Text/part0036.xhtml
17181 2019-06-27 10:40 OEBPS/Text/part0037.xhtml
5238 2019-06-27 10:40 OEBPS/Text/part0038.xhtml
561 2019-06-27 10:40 OEBPS/Text/part0039.xhtml
644 2019-06-27 10:40 OEBPS/Text/part0040.xhtml
1163 2019-06-27 10:40 OEBPS/Text/part0041.xhtml
1473 2019-06-27 10:40 OEBPS/Text/part0042.xhtml
38427 2019-06-27 10:40 OEBPS/Text/part0043.xhtml
90589 2019-06-27 10:40 OEBPS/Text/part0044.xhtml
51278 2019-06-27 10:40 OEBPS/Text/part0045.xhtml
58321 2019-06-27 10:40 OEBPS/Text/part0046.xhtml
29670 2019-06-27 10:40 OEBPS/Text/part0047.xhtml
12903 2019-06-27 10:40 OEBPS/Text/part0048.xhtml
7364 2019-06-27 10:40 OEBPS/toc.ncx
--------- -------
2422768 72 files
同时可以直接解压：
[littleye233@lymjrolt Downloads]$ unzip test.epub -d test_epub
Archive: test.epub
extracting: test_epub/mimetype
inflating: test_epub/META-INF/container.xml
inflating: test_epub/OEBPS/content.opf
inflating: test_epub/OEBPS/Images/cover00464.jpeg
inflating: test_epub/OEBPS/Images/image00456.jpeg
inflating: test_epub/OEBPS/Images/image00457.jpeg
inflating: test_epub/OEBPS/Images/image00458.jpeg
inflating: test_epub/OEBPS/Images/image00459.jpeg
inflating: test_epub/OEBPS/Images/image00460.jpeg
inflating: test_epub/OEBPS/Images/image00461.jpeg
inflating: test_epub/OEBPS/Images/image00462.jpeg
inflating: test_epub/OEBPS/Images/image00463.jpeg
inflating: test_epub/OEBPS/Styles/style0001.css
inflating: test_epub/OEBPS/Styles/style0002.css
inflating: test_epub/OEBPS/Styles/style0003.css
inflating: test_epub/OEBPS/Styles/style0004.css
inflating: test_epub/OEBPS/Styles/style0005.css
inflating: test_epub/OEBPS/Styles/style0006.css
inflating: test_epub/OEBPS/Styles/style0007.css
inflating: test_epub/OEBPS/Styles/style0008.css
inflating: test_epub/OEBPS/Styles/style0009.css
inflating: test_epub/OEBPS/Text/cover_page.xhtml
inflating: test_epub/OEBPS/Text/part0000.xhtml
inflating: test_epub/OEBPS/Text/part0001.xhtml
inflating: test_epub/OEBPS/Text/part0002.xhtml
inflating: test_epub/OEBPS/Text/part0003.xhtml
inflating: test_epub/OEBPS/Text/part0004.xhtml
inflating: test_epub/OEBPS/Text/part0005.xhtml
inflating: test_epub/OEBPS/Text/part0006.xhtml
inflating: test_epub/OEBPS/Text/part0007.xhtml
inflating: test_epub/OEBPS/Text/part0008.xhtml
inflating: test_epub/OEBPS/Text/part0009.xhtml
inflating: test_epub/OEBPS/Text/part0010.xhtml
inflating: test_epub/OEBPS/Text/part0011.xhtml
inflating: test_epub/OEBPS/Text/part0012.xhtml
inflating: test_epub/OEBPS/Text/part0013.xhtml
inflating: test_epub/OEBPS/Text/part0014.xhtml
inflating: test_epub/OEBPS/Text/part0015.xhtml
inflating: test_epub/OEBPS/Text/part0016.xhtml
inflating: test_epub/OEBPS/Text/part0017.xhtml
inflating: test_epub/OEBPS/Text/part0018.xhtml
inflating: test_epub/OEBPS/Text/part0019.xhtml
inflating: test_epub/OEBPS/Text/part0020.xhtml
inflating: test_epub/OEBPS/Text/part0021.xhtml
inflating: test_epub/OEBPS/Text/part0022.xhtml
inflating: test_epub/OEBPS/Text/part0023.xhtml
inflating: test_epub/OEBPS/Text/part0024.xhtml
inflating: test_epub/OEBPS/Text/part0025.xhtml
inflating: test_epub/OEBPS/Text/part0026.xhtml
inflating: test_epub/OEBPS/Text/part0027.xhtml
inflating: test_epub/OEBPS/Text/part0028.xhtml
inflating: test_epub/OEBPS/Text/part0029.xhtml
inflating: test_epub/OEBPS/Text/part0030.xhtml
inflating: test_epub/OEBPS/Text/part0031.xhtml
inflating: test_epub/OEBPS/Text/part0032.xhtml
inflating: test_epub/OEBPS/Text/part0033.xhtml
inflating: test_epub/OEBPS/Text/part0034.xhtml
inflating: test_epub/OEBPS/Text/part0035.xhtml
inflating: test_epub/OEBPS/Text/part0036.xhtml
inflating: test_epub/OEBPS/Text/part0037.xhtml
inflating: test_epub/OEBPS/Text/part0038.xhtml
inflating: test_epub/OEBPS/Text/part0039.xhtml
inflating: test_epub/OEBPS/Text/part0040.xhtml
inflating: test_epub/OEBPS/Text/part0041.xhtml
inflating: test_epub/OEBPS/Text/part0042.xhtml
inflating: test_epub/OEBPS/Text/part0043.xhtml
inflating: test_epub/OEBPS/Text/part0044.xhtml
inflating: test_epub/OEBPS/Text/part0045.xhtml
inflating: test_epub/OEBPS/Text/part0046.xhtml
inflating: test_epub/OEBPS/Text/part0047.xhtml
inflating: test_epub/OEBPS/Text/part0048.xhtml
inflating: test_epub/OEBPS/toc.ncx
为了更清楚地显示文件树结构，我们也可以使用 tree 命令 (这个命令在 Windows 中是内置的，在 Linux 中需要安装 tree 这个包，使用软件包管理器或编译安装均可) ：
[littleye233@lymjrolt test_epub]$ tree
.
├── META-INF
│ └── container.xml
├── mimetype
└── OEBPS
├── content.opf
├── Images
│ ├── cover00464.jpeg
│ ├── image00456.jpeg
│ ├── image00457.jpeg
│ ├── image00458.jpeg
│ ├── image00459.jpeg
│ ├── image00460.jpeg
│ ├── image00461.jpeg
│ ├── image00462.jpeg
│ └── image00463.jpeg
├── Styles
│ ├── style0001.css
│ ├── style0002.css
│ ├── style0003.css
│ ├── style0004.css
│ ├── style0005.css
│ ├── style0006.css
│ ├── style0007.css
│ ├── style0008.css
│ └── style0009.css
├── Text
│ ├── cover_page.xhtml
│ ├── part0000.xhtml
│ ├── part0001.xhtml
│ ├── part0002.xhtml
│ ├── part0003.xhtml
│ ├── part0004.xhtml
│ ├── part0005.xhtml
│ ├── part0006.xhtml
│ ├── part0007.xhtml
│ ├── part0008.xhtml
│ ├── part0009.xhtml
│ ├── part0010.xhtml
│ ├── part0011.xhtml
│ ├── part0012.xhtml
│ ├── part0013.xhtml
│ ├── part0014.xhtml
│ ├── part0015.xhtml
│ ├── part0016.xhtml
│ ├── part0017.xhtml
│ ├── part0018.xhtml
│ ├── part0019.xhtml
│ ├── part0020.xhtml
│ ├── part0021.xhtml
│ ├── part0022.xhtml
│ ├── part0023.xhtml
│ ├── part0024.xhtml
│ ├── part0025.xhtml
│ ├── part0026.xhtml
│ ├── part0027.xhtml
│ ├── part0028.xhtml
│ ├── part0029.xhtml
│ ├── part0030.xhtml
│ ├── part0031.xhtml
│ ├── part0032.xhtml
│ ├── part0033.xhtml
│ ├── part0034.xhtml
│ ├── part0035.xhtml
│ ├── part0036.xhtml
│ ├── part0037.xhtml
│ ├── part0038.xhtml
│ ├── part0039.xhtml
│ ├── part0040.xhtml
│ ├── part0041.xhtml
│ ├── part0042.xhtml
│ ├── part0043.xhtml
│ ├── part0044.xhtml
│ ├── part0045.xhtml
│ ├── part0046.xhtml
│ ├── part0047.xhtml
│ └── part0048.xhtml
└── toc.ncx
5 directories, 72 files
到这里我们大概就能猜出来：
META-INF 文件夹：里面存放的应该是“容器” (也就是这个 ePub 文件) 的相关配置文件；mimetype 文件：里面定义了这个文件的类型为 “ePub” (其中 “MIME” 是 “Multipurpose Internet Mail Extensions” 的缩写，从字面上也能看出其具有指示 “Extension” 的机能) ；OEBPS 文件夹：虽暂不知其确切含义，但应存放 ePub 的文字、图片以及其他的界面数据；
content.opf 文件：里面存放的应该是目录信息——或是定义各种文件的“次序”；Images Styles 和 Text 文件夹：明显分别存放图片、层叠样式表和文字数据；toc.ncx 文件：可能是真正的目录 (“toc” 是 “table of contents” 的缩写)。接下来我们将挨个分析。
先看 META-INF/container.xml ：
[littleye233@lymjrolt test_epub]$ file META-INF/container.xml
META-INF/container.xml: XML 1.0 document, ASCII text
输出其内容：
<?xml version="1.0" encoding="UTF-8"?>
<container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container">
<rootfiles>
<rootfile full-path="OEBPS/content.opf" media-type="application/oebps-package+xml"/> </rootfiles>
</container>
显然是一个标准的 XML 文件，其中我们可以注意到 /container/rootfiles/rootfile[@class=‘full-path‘][1] 中定义了一个我们之前认定的目录文件，但此处可以规范化，故这个文件在大多数 ePub 档中应该是相同的。
接下来看 mimetype 文件：
[littleye233@lymjrolt test_epub]$ cat mimetype
application/epub+zip
这也是相当显然的，也不再赘述。
再看 OEBPS/content.opf ：
[littleye233@lymjrolt test_epub]$ file OEBPS/content.opf
OEBPS/content.opf: XML 1.0 document, Unicode text, UTF-8 text, with very long lines (504)
这也是一个 XML 文件，令人惊讶的是 file 命令竟能看出这个文件中最长的行有 504 个字符，属实让人害怕。
<?xml version="1.0" encoding="utf-8"?>
<package xmlns="http://www.idpf.org/2007/opf" version="2.0" unique-identifier="uid">
<metadata xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:opf="http://www.idpf.org/2007/opf">
<dc:title opf:file-as="kafeiguantuilishijianbuxilie（quansiben）">咖啡馆推理事件簿系列（全四本）</dc:title>
<dc:language>zh</dc:language>
<dc:identifier id="uid">3899198450</dc:identifier>
<dc:creator opf:file-as="（ri）gangqizuomo">（日）冈崎琢磨</dc:creator>
<dc:date opf:event="publication">2018-03-15</dc:date>
<!-- Extra MetaData from RESC
<dc:coverage/>
-->
<meta name="cover" content="x_cover-image"/>
<meta name="output encoding" content="utf-8"/>
<meta name="primary-writing-mode" content="horizontal-lr"/>
<!-- BEGIN INFORMATION ONLY
<meta name="Cover ThumbNail Image" content="Images/image00466.jpeg" />
<meta name="Drm Ebookbase Book Id" content="0006008690412" />
<meta name="ASIN" content="B07BFTVX98" />
<meta name="Creator-Software" content="201" />
<meta name="Author-Pronunciation" content="（ri）gangqizuomo" />
<meta name="Embedded-Record-Count" content="11" />
<meta name="Unknown_(403)_(hex)" content="00" />
<meta name="HasFakeCover" content="0" />
<meta name="Creator-Major-Version" content="2" />
<meta name="cdeType" content="EBOK" />
<meta name="override-kindle-fonts" content="false" />
<meta name="CDEContentKey" content="B07BFTVX98" />
<meta name="Compression-Upgraded" content="Source-Target:c1-c2 KT_Version:2.9 Build:0805-4a0c57c" />
<meta name="HD-Media-Containers-Info" content="2400x3840:0-11|" />
<meta name="548 (hex)" content="496e4d656d6f7279" />
<meta name="Unknown_(407)_(hex)" content="0000000000000000" />
<meta name="Amazon_Creator_Info" content="kjw" />
<meta name="Clipping-Limit" content="100" />
<meta name="Tamper-Proof-Keys_(hex)" content="01000000d000000001940000000191000000019500000001960000000197" />
<meta name="Title-Pronunciation" content="kafeiguantuilishijianbuxilie（quansiben）" />
<meta name="Creator-Minor-Version" content="9" />
<meta name="MetadataResourceURI" content="kindle:embed:000A" />
<meta name="Updated_Title" content="咖啡馆推理事件簿系列（全四本）" />
<meta name="Ownership-Type_(hex)" content="00" />
<meta name="547 (hex)" content="496e4d656d6f7279" />
<meta name="Content-Language-Tag" content="zh" />
<meta name="sample" content="0" />
<meta name="Metadata-Record-Offset" content="4294967295" />
<meta name="Creator-Build-Tag" content="0721-dedaf5" />
<meta name="Publisher-Pronunciation" content="xiandaichubanshe" />
<meta name="StartOffset" content="4294967295" />
<meta name="Watermark_(hex)" content="6174763a6b696e3a323a49396e41307a4239625565766a514961583462736b66476a394535335a51616a696368585638364447746b65544379504d504c4d75445a35524f39676b584d35515a6433694f424b5531546643766f5a62507763705a6b49486f6f366a6639785944327a4158494263536c495879676b6a38616b566e4763327a2b2b50434c454c464b2b4e30495a4556437a6331516f656f4451546b3865374a6f61696251526d6f682b7574586b3661466a554477704a3165636c68665367414a35664745413a68614f61636b496839662b61786c457733397665774b32554a57453d" />
<meta name="Text-to-Speech-Disabled" content="0" />
<meta name="Font-Signature_(hex)" content="0300000000480f08100000000000008000200000000000000000000000000000bef4edec01b701d7409440984099409c409d40a64a804c9c608160826080608b60e8618b60cd60c661aa61f361d661e9629c73df0213c9021fd90173cd01429f037e9a037e8c037e81037e9f" />
<meta name="Rental-Expiration-Time" content="0000000000000000" />
<meta name="Container_Id" content="ZkM0" />
<meta name="Mobi8-Boundary-Section" content="420" />
<meta name="Creator-Build-Number" content="0" />
END INFORMATION ONLY -->
</metadata>
<manifest>
<item id="x_cover" media-type="application/xhtml+xml" href="Text/cover_page.xhtml"/>
<item id="x_TableOfContents" media-type="application/xhtml+xml" href="Text/part0000.xhtml"/>
<item id="x_a1cover.html" media-type="application/xhtml+xml" href="Text/part0001.xhtml"/>
<item id="x_a1bookname" media-type="application/xhtml+xml" href="Text/part0002.xhtml"/>
<item id="x_a1TableOfContents" media-type="application/xhtml+xml" href="Text/part0003.xhtml"/>
<item id="x_a1Chapter001" media-type="application/xhtml+xml" href="Text/part0004.xhtml"/>
<item id="x_a1Chapter002" media-type="application/xhtml+xml" href="Text/part0005.xhtml"/>
<item id="x_a1Chapter003" media-type="application/xhtml+xml" href="Text/part0006.xhtml"/>
<item id="x_a1Chapter004" media-type="application/xhtml+xml" href="Text/part0007.xhtml"/>
<item id="x_a1Chapter005" media-type="application/xhtml+xml" href="Text/part0008.xhtml"/>
<item id="x_a1Chapter006" media-type="application/xhtml+xml" href="Text/part0009.xhtml"/>
<item id="x_a1Chapter007" media-type="application/xhtml+xml" href="Text/part0010.xhtml"/>
<item id="x_a1Chapter008" media-type="application/xhtml+xml" href="Text/part0011.xhtml"/>
<item id="x_a1Chapter009" media-type="application/xhtml+xml" href="Text/part0012.xhtml"/>
<item id="x_a1Chapter010" media-type="application/xhtml+xml" href="Text/part0013.xhtml"/>
<item id="x_a2cover.html" media-type="application/xhtml+xml" href="Text/part0014.xhtml"/>
<item id="x_a2bookname" media-type="application/xhtml+xml" href="Text/part0015.xhtml"/>
<item id="x_a2TableOfContents" media-type="application/xhtml+xml" href="Text/part0016.xhtml"/>
<item id="x_a2Chapter001" media-type="application/xhtml+xml" href="Text/part0017.xhtml"/>
<item id="x_a2Chapter002" media-type="application/xhtml+xml" href="Text/part0018.xhtml"/>
<item id="x_a2Chapter003" media-type="application/xhtml+xml" href="Text/part0019.xhtml"/>
<item id="x_a2Chapter004" media-type="application/xhtml+xml" href="Text/part0020.xhtml"/>
<item id="x_a2Chapter005" media-type="application/xhtml+xml" href="Text/part0021.xhtml"/>
<item id="x_a2Chapter006" media-type="application/xhtml+xml" href="Text/part0022.xhtml"/>
<item id="x_a2Chapter007" media-type="application/xhtml+xml" href="Text/part0023.xhtml"/>
<item id="x_a2Chapter008" media-type="application/xhtml+xml" href="Text/part0024.xhtml"/>
<item id="x_a2Chapter009" media-type="application/xhtml+xml" href="Text/part0025.xhtml"/>
<item id="x_a2Chapter010" media-type="application/xhtml+xml" href="Text/part0026.xhtml"/>
<item id="x_a3cover.html" media-type="application/xhtml+xml" href="Text/part0027.xhtml"/>
<item id="x_a3bookname" media-type="application/xhtml+xml" href="Text/part0028.xhtml"/>
<item id="x_a3TableOfContents" media-type="application/xhtml+xml" href="Text/part0029.xhtml"/>
<item id="x_a3Chapter001" media-type="application/xhtml+xml" href="Text/part0030.xhtml"/>
<item id="x_a3Chapter002" media-type="application/xhtml+xml" href="Text/part0031.xhtml"/>
<item id="x_a3Chapter003" media-type="application/xhtml+xml" href="Text/part0032.xhtml"/>
<item id="x_a3Chapter004" media-type="application/xhtml+xml" href="Text/part0033.xhtml"/>
<item id="x_a3Chapter005" media-type="application/xhtml+xml" href="Text/part0034.xhtml"/>
<item id="x_a3Chapter006" media-type="application/xhtml+xml" href="Text/part0035.xhtml"/>
<item id="x_a3Chapter007" media-type="application/xhtml+xml" href="Text/part0036.xhtml"/>
<item id="x_a3Chapter008" media-type="application/xhtml+xml" href="Text/part0037.xhtml"/>
<item id="x_a3Chapter009" media-type="application/xhtml+xml" href="Text/part0038.xhtml"/>
<item id="x_a4cover.html" media-type="application/xhtml+xml" href="Text/part0039.xhtml"/>
<item id="x_a4bookname" media-type="application/xhtml+xml" href="Text/part0040.xhtml"/>
<item id="x_a4TableOfContents" media-type="application/xhtml+xml" href="Text/part0041.xhtml"/>
<item id="x_a4Chapter001" media-type="application/xhtml+xml" href="Text/part0042.xhtml"/>
<item id="x_a4Chapter002" media-type="application/xhtml+xml" href="Text/part0043.xhtml"/>
<item id="x_a4Chapter003" media-type="application/xhtml+xml" href="Text/part0044.xhtml"/>
<item id="x_a4Chapter004" media-type="application/xhtml+xml" href="Text/part0045.xhtml"/>
<item id="x_a4Chapter005" media-type="application/xhtml+xml" href="Text/part0046.xhtml"/>
<item id="x_a4Chapter006" media-type="application/xhtml+xml" href="Text/part0047.xhtml"/>
<item id="x_a4Chapter007" media-type="application/xhtml+xml" href="Text/part0048.xhtml"/>
<item id="item50" media-type="text/css" href="Styles/style0001.css"/>
<item id="item51" media-type="text/css" href="Styles/style0002.css"/>
<item id="item52" media-type="text/css" href="Styles/style0003.css"/>
<item id="item53" media-type="text/css" href="Styles/style0004.css"/>
<item id="item54" media-type="text/css" href="Styles/style0005.css"/>
<item id="item55" media-type="text/css" href="Styles/style0006.css"/>
<item id="item56" media-type="text/css" href="Styles/style0007.css"/>
<item id="item57" media-type="text/css" href="Styles/style0008.css"/>
<item id="item58" media-type="text/css" href="Styles/style0009.css"/>
<item id="item59" media-type="image/jpeg" href="Images/image00456.jpeg"/>
<item id="item60" media-type="image/jpeg" href="Images/image00457.jpeg"/>
<item id="item61" media-type="image/jpeg" href="Images/image00458.jpeg"/>
<item id="item62" media-type="image/jpeg" href="Images/image00459.jpeg"/>
<item id="item63" media-type="image/jpeg" href="Images/image00460.jpeg"/>
<item id="item64" media-type="image/jpeg" href="Images/image00461.jpeg"/>
<item id="item65" media-type="image/jpeg" href="Images/image00462.jpeg"/>
<item id="item66" media-type="image/jpeg" href="Images/image00463.jpeg"/>
<item id="x_cover-image" media-type="image/jpeg" href="Images/cover00464.jpeg"/>
<item id="ncx" media-type="application/x-dtbncx+xml" href="toc.ncx"/>
</manifest>
<spine toc="ncx">
<itemref idref="x_cover" linear="no"/>
<itemref idref="x_TableOfContents" linear="yes"/>
<itemref idref="x_a1cover.html" linear="yes"/>
<itemref idref="x_a1bookname" linear="yes"/>
<itemref idref="x_a1TableOfContents" linear="yes"/>
<itemref idref="x_a1Chapter001" linear="yes"/>
<itemref idref="x_a1Chapter002" linear="yes"/>
<itemref idref="x_a1Chapter003" linear="yes"/>
<itemref idref="x_a1Chapter004" linear="yes"/>
<itemref idref="x_a1Chapter005" linear="yes"/>
<itemref idref="x_a1Chapter006" linear="yes"/>
<itemref idref="x_a1Chapter007" linear="yes"/>
<itemref idref="x_a1Chapter008" linear="yes"/>
<itemref idref="x_a1Chapter009" linear="yes"/>
<itemref idref="x_a1Chapter010" linear="yes"/>
<itemref idref="x_a2cover.html" linear="yes"/>
<itemref idref="x_a2bookname" linear="yes"/>
<itemref idref="x_a2TableOfContents" linear="yes"/>
<itemref idref="x_a2Chapter001" linear="yes"/>
<itemref idref="x_a2Chapter002" linear="yes"/>
<itemref idref="x_a2Chapter003" linear="yes"/>
<itemref idref="x_a2Chapter004" linear="yes"/>
<itemref idref="x_a2Chapter005" linear="yes"/>
<itemref idref="x_a2Chapter006" linear="yes"/>
<itemref idref="x_a2Chapter007" linear="yes"/>
<itemref idref="x_a2Chapter008" linear="yes"/>
<itemref idref="x_a2Chapter009" linear="yes"/>
<itemref idref="x_a2Chapter010" linear="yes"/>
<itemref idref="x_a3cover.html" linear="yes"/>
<itemref idref="x_a3bookname" linear="yes"/>
<itemref idref="x_a3TableOfContents" linear="yes"/>
<itemref idref="x_a3Chapter001" linear="yes"/>
<itemref idref="x_a3Chapter002" linear="yes"/>
<itemref idref="x_a3Chapter003" linear="yes"/>
<itemref idref="x_a3Chapter004" linear="yes"/>
<itemref idref="x_a3Chapter005" linear="yes"/>
<itemref idref="x_a3Chapter006" linear="yes"/>
<itemref idref="x_a3Chapter007" linear="yes"/>
<itemref idref="x_a3Chapter008" linear="yes"/>
<itemref idref="x_a3Chapter009" linear="yes"/>
<itemref idref="x_a4cover.html" linear="yes"/>
<itemref idref="x_a4bookname" linear="yes"/>
<itemref idref="x_a4TableOfContents" linear="yes"/>
<itemref idref="x_a4Chapter001" linear="yes"/>
<itemref idref="x_a4Chapter002" linear="yes"/>
<itemref idref="x_a4Chapter003" linear="yes"/>
<itemref idref="x_a4Chapter004" linear="yes"/>
<itemref idref="x_a4Chapter005" linear="yes"/>
<itemref idref="x_a4Chapter006" linear="yes"/>
<itemref idref="x_a4Chapter007" linear="yes"/>
</spine>
<tours>
</tours>
<guide>
<reference type="text" title="Start" href="Text/part0004.xhtml"/>
<reference type="toc" title="Table of Contents" href="Text/part0000.xhtml"/>
<reference type="cover" title="Cover" href="Text/cover_page.xhtml"/>
</guide>
</package>
说明我之前并没有猜错，这个文件存放的是超越“目录”的东西，而是“次序”——更进一步说。是“索引”。这个文件类似于其他文件格式或目录树中的 index.* ，将 ePub 中的各种数据编上号码，同时这里也定义了标题、语言、作者、出版 (发布) 日期等元信息。至于之前看到的超长行，似乎是一种十六进制的水印 (watermark) ，或许是为了防侵权等。
其中的 /package/manifest/item 定义了所有的索引，以及文件对应的类型； /package/spine/itemref 暂不知进一步的作用，但从中可看出能定义是否“线性” (linear) ； /package/guide/reference 定义了 ePub 的封面等索引，可供文件管理器和 ePub 阅读器使用 (显示预览页) 。
再看 OEBPS/toc.ncx ：
[littleye233@lymjrolt test_epub]$ file OEBPS/toc.ncx
OEBPS/toc.ncx: XML 1.0 document, Unicode text, UTF-8 text
感觉再讨论文件类型已经无关紧要了。再次查看内容：
<?xml version="1.0" encoding="utf-8"?>
<ncx xmlns="http://www.daisy.org/z3986/2005/ncx/" version="2005-1" xml:lang="zh">
<head>
<meta content="3899198450" name="dtb:uid"/>
<meta content="2" name="dtb:depth"/>
<meta content="mobiunpack.py" name="dtb:generator"/>
<meta content="0" name="dtb:totalPageCount"/>
<meta content="0" name="dtb:maxPageNumber"/>
</head>
<docTitle>
<text>咖啡馆推理事件簿系列（全四本）</text>
</docTitle>
<navMap>
<navPoint id="np_1" playOrder="1">
<navLabel>
<text>总目录</text>
</navLabel>
<content src="Text/part0000.xhtml"/>
</navPoint>
<navPoint id="np_2" playOrder="2">
<navLabel>
<text>咖啡馆推理事件簿：下次见面时，请让我品尝你煮的咖啡</text>
</navLabel>
<content src="Text/part0001.xhtml"/>
<navPoint id="np_3" playOrder="3">
<navLabel>
<text>序章</text>
</navLabel>
<content src="Text/part0005.xhtml"/>
</navPoint>
<navPoint id="np_4" playOrder="4">
<navLabel>
<text>一 事件始于第二次光顾</text>
</navLabel>
<content src="Text/part0006.xhtml"/>
</navPoint>
<navPoint id="np_5" playOrder="5">
<navLabel>
<text>二 Bittersweet Black</text>
</navLabel>
<content src="Text/part0007.xhtml"/>
</navPoint>
<navPoint id="np_6" playOrder="6">
<navLabel>
<text>三 隐藏在乳白色中的心</text>
</navLabel>
<content src="Text/part0008.xhtml"/>
</navPoint>
<navPoint id="np_7" playOrder="7">
<navLabel>
<text>四 棋盘上的狩猎</text>
</navLabel>
<content src="Text/part0009.xhtml"/>
</navPoint>
<navPoint id="np_8" playOrder="8">
<navLabel>
<text>五 past，present，f******？</text>
</navLabel>
<content src="Text/part0010.xhtml"/>
</navPoint>
<navPoint id="np_9" playOrder="9">
<navLabel>
<text>六 Animals in the closed room</text>
</navLabel>
<content src="Text/part0011.xhtml"/>
</navPoint>
<navPoint id="np_10" playOrder="10">
<navLabel>
<text>七 下次见面时，请让我品尝你煮的咖啡</text>
</navLabel>
<content src="Text/part0012.xhtml"/>
</navPoint>
<navPoint id="np_11" playOrder="11">
<navLabel>
<text>终章</text>
</navLabel>
<content src="Text/part0013.xhtml"/>
</navPoint>
</navPoint>
<navPoint id="np_12" playOrder="12">
<navLabel>
<text>咖啡馆推理事件簿2：她梦到了欧蕾咖啡</text>
</navLabel>
<content src="Text/part0014.xhtml"/>
<navPoint id="np_13" playOrder="13">
<navLabel>
<text>序曲 她的梦</text>
</navLabel>
<content src="Text/part0018.xhtml"/>
</navPoint>
<navPoint id="np_14" playOrder="14">
<navLabel>
<text>第一章 敬启致未来的你</text>
</navLabel>
<content src="Text/part0019.xhtml"/>
</navPoint>
<navPoint id="np_15" playOrder="15">
<navLabel>
<text>第二章 狐狸的迷惑</text>
</navLabel>
<content src="Text/part0020.xhtml"/>
</navPoint>
<navPoint id="np_16" playOrder="16">
<navLabel>
<text>第三章 打碎乳白色的心</text>
</navLabel>
<content src="Text/part0021.xhtml"/>
</navPoint>
<navPoint id="np_17" playOrder="17">
<navLabel>
<text>第四章 咖啡侦探蕾拉事件簿</text>
</navLabel>
<content src="Text/part0022.xhtml"/>
</navPoint>
<navPoint id="np_18" playOrder="18">
<navLabel>
<text>第五章 （She Wanted To Be）WANTED</text>
</navLabel>
<content src="Text/part0023.xhtml"/>
</navPoint>
<navPoint id="np_19" playOrder="19">
<navLabel>
<text>第六章 the Sky Occluded in the Sun</text>
</navLabel>
<content src="Text/part0024.xhtml"/>
</navPoint>
<navPoint id="np_20" playOrder="20">
<navLabel>
<text>第七章 在星空之下同命相连</text>
</navLabel>
<content src="Text/part0025.xhtml"/>
</navPoint>
<navPoint id="np_21" playOrder="21">
<navLabel>
<text>终章 她梦到了欧蕾咖啡</text>
</navLabel>
<content src="Text/part0026.xhtml"/>
</navPoint>
</navPoint>
<navPoint id="np_22" playOrder="22">
<navLabel>
<text>咖啡馆推理事件簿3：扰人心神的咖啡</text>
</navLabel>
<content src="Text/part0027.xhtml"/>
<navPoint id="np_23" playOrder="23">
<navLabel>
<text>序曲 五年前</text>
</navLabel>
<content src="Text/part0031.xhtml"/>
</navPoint>
<navPoint id="np_24" playOrder="24">
<navLabel>
<text>第一章 参加大赛</text>
</navLabel>
<content src="Text/part0032.xhtml"/>
</navPoint>
<navPoint id="np_25" playOrder="25">
<navLabel>
<text>第二章 前夜</text>
</navLabel>
<content src="Text/part0033.xhtml"/>
</navPoint>
<navPoint id="np_26" playOrder="26">
<navLabel>
<text>第三章 第一天</text>
</navLabel>
<content src="Text/part0034.xhtml"/>
</navPoint>
<navPoint id="np_27" playOrder="27">
<navLabel>
<text>第四章 第二天</text>
</navLabel>
<content src="Text/part0035.xhtml"/>
</navPoint>
<navPoint id="np_28" playOrder="28">
<navLabel>
<text>第五章 真相</text>
</navLabel>
<content src="Text/part0036.xhtml"/>
</navPoint>
<navPoint id="np_29" playOrder="29">
<navLabel>
<text>第六章 日后</text>
</navLabel>
<content src="Text/part0037.xhtml"/>
</navPoint>
<navPoint id="np_30" playOrder="30">
<navLabel>
<text>尾声 五年前</text>
</navLabel>
<content src="Text/part0038.xhtml"/>
</navPoint>
</navPoint>
<navPoint id="np_31" playOrder="31">
<navLabel>
<text>咖啡馆推理事件簿4：休闲时光的五种风味</text>
</navLabel>
<content src="Text/part0039.xhtml"/>
<navPoint id="np_32" playOrder="32">
<navLabel>
<text>午后三点前的无聊风景</text>
</navLabel>
<content src="Text/part0043.xhtml"/>
</navPoint>
<navPoint id="np_33" playOrder="33">
<navLabel>
<text>帕列塔之恋</text>
</navLabel>
<content src="Text/part0044.xhtml"/>
</navPoint>
<navPoint id="np_34" playOrder="34">
<navLabel>
<text>消失的礼物飞镖</text>
</navLabel>
<content src="Text/part0045.xhtml"/>
</navPoint>
<navPoint id="np_35" playOrder="35">
<navLabel>
<text>可视化的原生艺术</text>
</navLabel>
<content src="Text/part0046.xhtml"/>
</navPoint>
<navPoint id="np_36" playOrder="36">
<navLabel>
<text>在塔列兰咖啡馆的庭院里</text>
</navLabel>
<content src="Text/part0047.xhtml"/>
</navPoint>
<navPoint id="np_37" playOrder="37">
<navLabel>
<text>特别篇 如释重负</text>
</navLabel>
<content src="Text/part0048.xhtml"/>
</navPoint>
</navPoint>
</navMap>
</ncx>
我们不妨将目光转向较为重要的“目录”的定义上。为了方便观察，笔者偷点懒，使用桌面环境中自带的阅读器观察：
从中可以看出目录是二层结构，恰好和 OEBPS/toc.ncx 中的定义保持一致。而其中的部分重要属性均可“望文生义”，此处不再进一步研究。
最后剩下的是图片、文字和层叠样式表。虽然这部分是在整个 ePub 文件中占比最大也可以说是最重要的部分，但由于这一块的内容实在是太过直白，再讲下去恐怕要开始补习 HTML 和 CSS 知识了，故同样略去。
根据上文中的简要探究， ePub 是一种以 XML 文件格式为配置文件类型的、包含有图片及文字等数据的、以压缩档为本质的文件格式。查阅相关资料后可知其实质与上文中分析类似。
而通过上文的分析，我们初步体验到分析一种陌生文件格式的规律和技巧，可以用于后续对更复杂的文件格式的探究。
但最后，别忘了把那个 ePub 文件的名字改回来 XD ：
[littleye233@lymjrolt Downloads]$ mv test.epub 咖啡馆推理事件簿系列（全四本）.epub
【完】
此处为 XPath 语法，用于描述类 XML 文件各种元素的位置，后文类似者不再注明。 ??
原文：https://www.cnblogs.com/littleye233/p/15178306.html