xmlstarlet "does not work" 用于带有名称空间的 XML

Question

我正在使用媒体信息来获取有关电影的一些xml信息：

mediainfo --Output=XML Krtek\ a\ buldozer-jdvwqZUEbhc.mkv  | xmlstarlet format

哪个输出是：

<?xml version="1.0" encoding="UTF-8"?>
<MediaInfo xmlns="https://mediaarea.net/mediainfo" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://mediaarea.net/mediainfo https://mediaarea.net/mediainfo/mediainfo_2_0.xsd" version="2.0">
  <creatingLibrary version="18.03" url="https://mediaarea.net/MediaInfo">MediaInfoLib</creatingLibrary>
  <media ref="Krtek a buldozer-jdvwqZUEbhc.mkv">
    <track type="General">
      <UniqueID>101120522676894244607292274887483611459</UniqueID>
      <VideoCount>1</VideoCount>
      <AudioCount>1</AudioCount>
      <FileExtension>mkv</FileExtension>
      <Format>Matroska</Format>
      <Format_Version>4</Format_Version>
      <FileSize>60132643</FileSize>
      <Duration>374.101</Duration>
      <OverallBitRate>1285912</OverallBitRate>
      <FrameRate>25.000</FrameRate>
      <FrameCount>9352</FrameCount>
      <IsStreamable>Yes</IsStreamable>
      <File_Modified_Date>UTC 2018-10-15 07:09:29</File_Modified_Date>
      <File_Modified_Date_Local>2018-10-15 09:09:29</File_Modified_Date_Local>
      <Encoded_Application>Lavf57.71.100</Encoded_Application>
      <Encoded_Library>Lavf57.71.100</Encoded_Library>
      <extra>
        <ErrorDetectionType>Per level 1</ErrorDetectionType>
      </extra>
    </track>
    <track type="Video">
      <StreamOrder>0</StreamOrder>
      <ID>1</ID>
      <UniqueID>1</UniqueID>
      <Format>AVC</Format>
      <Format_Profile>High</Format_Profile>
      <Format_Level>4</Format_Level>
      <Format_Settings_CABAC>Yes</Format_Settings_CABAC>
      <Format_Settings_RefFrames>3</Format_Settings_RefFrames>
      <CodecID>V_MPEG4/ISO/AVC</CodecID>
      <Duration>374.080000000</Duration>
      <Width>1920</Width>
      <Height>1080</Height>
      <Stored_Height>1088</Stored_Height>
      <Sampled_Width>1920</Sampled_Width>
      <Sampled_Height>1080</Sampled_Height>
      <PixelAspectRatio>1.000</PixelAspectRatio>
      <DisplayAspectRatio>1.778</DisplayAspectRatio>
      <FrameRate_Mode>CFR</FrameRate_Mode>
      <FrameRate_Mode_Original>VFR</FrameRate_Mode_Original>
      <FrameRate>25.000</FrameRate>
      <FrameCount>9352</FrameCount>
      <ColorSpace>YUV</ColorSpace>
      <ChromaSubsampling>4:2:0</ChromaSubsampling>
      <BitDepth>8</BitDepth>
      <ScanType>Progressive</ScanType>
      <Delay>0.000</Delay>
      <Default>Yes</Default>
      <Forced>No</Forced>
      <colour_range>Limited</colour_range>
      <colour_description_present>Yes</colour_description_present>
      <colour_primaries>BT.709</colour_primaries>
      <transfer_characteristics>BT.709</transfer_characteristics>
      <matrix_coefficients>BT.709</matrix_coefficients>
    </track>
    <track type="Audio">
      <StreamOrder>1</StreamOrder>
      <ID>2</ID>
      <UniqueID>2</UniqueID>
      <Format>Opus</Format>
      <CodecID>A_OPUS</CodecID>
      <Duration>374.101000000</Duration>
      <Channels>2</Channels>
      <ChannelPositions>Front: L R</ChannelPositions>
      <SamplingRate>48000</SamplingRate>
      <SamplingCount>17956848</SamplingCount>
      <BitDepth>32</BitDepth>
      <Compression_Mode>Lossy</Compression_Mode>
      <Delay>0.000</Delay>
      <Delay_Source>Container</Delay_Source>
      <Language>en</Language>
      <Default>Yes</Default>
      <Forced>No</Forced>
    </track>
  </media>
</MediaInfo>

现在说我要获取所有ID：

... | xmlstarlet sel -t -v "//ID"

没有打印任何内容。什么？为什么？事实证明，如果我从第二行的标签中删除所有参数，则相同的选择命令将起作用。现在我明白了，xmlstarlet（可能）工作得很好，我只是缺少一些神奇的标志或语法，以便它可以处理具有定义的名称空间的 xmls。有人可以建议吗？

Answer 1

您需要使用带 -N 选项的命名空间，并在查询中使用它，例如 <namespace>:<xpath>:

... | xmlstarlet sel -N n="https://mediaarea.net/mediainfo" -t -v "//n:ID"

来自帮助页面：

-N <name>=<value>
- predefine namespaces (name without 'xmlns:')
ex: xsql=urn:oracle-xsql
Multiple -N options are allowed.

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