xml - 使用 xmlstarlet 提取数据

Question

我想使用 xmlstarlet 提取 .xml 文件的内容，并将其写入变量。

.xml 文件是 mediainfo 的输出，例如我想从视频中提取帧速率，问题是标签( <BitRate> )命名相同，唯一的区别是它周围的 <track type="Video"></track> 。

我想避免使用 sed 的正则表达式方法，因为我认为程序更好并且更容易处理。我想避免像获取第二个比特率条目这样的事情。它不是 Bash 脚本中的第一个，当然也不是最后一个 xml 操作。

信息的插入非常适合(例如):

xmlstarlet -q ed -L -P -u "/movie1/videoframerate" -v "123456 Kb/s" ./test.xml

这是 mediainfo 的典型 XML 输出:

<?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="17.12" url="https://mediaarea.net/MediaInfo">MediaInfoLib</creatingLibrary>
<media ref="/path/to/file.mkv">

<track type="General">
 <UniqueID>174213452352936523294326454020021161878</UniqueID>
 <VideoCount>1</VideoCount>
 <AudioCount>2</AudioCount>
 <FileExtension>mkv</FileExtension>
 <Format>Matroska</Format>
 <Format_Version>2</Format_Version>
 <FileSize>7655754558</FileSize>
 <Duration>7087.808</Duration>
 <OverallBitRate>8641041</OverallBitRate>
 <FrameRate>23.976</FrameRate>
 <FrameCount>169937</FrameCount>
 <StreamSize>152359808</StreamSize>
 <IsStreamable>Yes</IsStreamable>
 <Encoded_Date>UTC 2010-09-04 22:54:43</Encoded_Date>
 <File_Modified_Date>UTC 2010-09-07 07:56:15</File_Modified_Date>
 <File_Modified_Date_Local>2010-09-07 07:56:15</File_Modified_Date_Local>
 <Encoded_Application>mkvmerge v3.3.0 (&apos;Language&apos;) built on Mar 24 2010 14:59:24</Encoded_Application>
 <Encoded_Library>libebml v0.8.0 + libmatroska v0.9.0</Encoded_Library>
</track>

<track type="Video">
 <StreamOrder>0</StreamOrder>
 <ID>1</ID>
 <UniqueID>1959315852</UniqueID>
 <Format>AVC</Format>
 <Format_Profile>Main</Format_Profile>
 <Format_Level>4.1</Format_Level>
 <Format_Settings_CABAC>No</Format_Settings_CABAC>
 <Format_Settings_RefFrames>4</Format_Settings_RefFrames>
 <CodecID>V_MPEG4/ISO/AVC</CodecID>
 <Duration>7087.796</Duration>
 <BitRate>7357000</BitRate>
 <Width>1280</Width>
 <Height>544</Height>
 <Sampled_Width>1280</Sampled_Width>
 <Sampled_Height>544</Sampled_Height>
 <PixelAspectRatio>1.000</PixelAspectRatio>
 <DisplayAspectRatio>2.353</DisplayAspectRatio>
 <FrameRate_Mode>CFR</FrameRate_Mode>
 <FrameRate>23.976</FrameRate>
 <FrameCount>169937</FrameCount>
 <ColorSpace>YUV</ColorSpace>
 <ChromaSubsampling>4:2:0</ChromaSubsampling>
 <BitDepth>8</BitDepth>
 <ScanType>Progressive</ScanType>
 <Delay>0.000</Delay>
 <StreamSize>6369345470</StreamSize>
 <Encoded_Library>x264 - core 93 r1542 5b86182</Encoded_Library>
 <Encoded_Library_Name>x264</Encoded_Library_Name>
 <Encoded_Library_Version>core 93 r1542 5b86182</Encoded_Library_Version>
 <Encoded_Library_Settings>cabac=0 / ref=1 / deblock=0:-1:-1 / analyse=0:0 / me=dia / subme=0 / psy=1 / psy_rd=0.00:0.00 / mixed_ref=0 / me_range=16 / chroma_me=1 / trellis=0 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=0 / threads=6 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=1 / wpredb=1 / wpredp=0 / keyint=250 / keyint_min=25 / scenecut=0 / intra_refresh=0 / rc=2pass / mbtree=0 / bitrate=7357 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / pb_ratio=1.30 / aq=0</Encoded_Library_Settings>
 <Default>Yes</Default>
 <Forced>No</Forced>
</track>

<track type="Audio" typeorder="1">
 <StreamOrder>1</StreamOrder>
 <ID>2</ID>
 <UniqueID>2957281200</UniqueID>
 <Format>AC-3</Format>
 <Format_Settings_Endianness>Big</Format_Settings_Endianness>
 <CodecID>A_AC3</CodecID>
 <Duration>7087.808</Duration>
 <BitRate_Mode>CBR</BitRate_Mode>
 <BitRate>640000</BitRate>
 <Channels>6</Channels>
 <ChannelPositions>Front: L C R, Side: L R, LFE</ChannelPositions>
 <ChannelLayout>L C R LFE Ls Rs</ChannelLayout>
 <SamplesPerFrame>1536</SamplesPerFrame>
 <SamplingRate>48000</SamplingRate>
 <SamplingCount>340214784</SamplingCount>
 <FrameRate>31.250</FrameRate>
 <BitDepth>16</BitDepth>
 <Compression_Mode>Lossy</Compression_Mode>
 <Delay>0.000</Delay>
 <Delay_Source>Container</Delay_Source>
 <StreamSize>567024640</StreamSize>
 <StreamSize_Proportion>0.07407</StreamSize_Proportion>
 <Language>de</Language>
 <ServiceKind>CM</ServiceKind>
 <Default>Yes</Default>
 <Forced>No</Forced>
 <extra>
  <bsid>8</bsid>
  <dialnorm>-31</dialnorm>
  <dialnorm_String>-31 dB</dialnorm_String>
  <acmod>7</acmod>
  <lfeon>1</lfeon>
  <dialnorm_Average>-31</dialnorm_Average>
  <dialnorm_Average_String>-31 dB</dialnorm_Average_String>
  <dialnorm_Minimum>-31</dialnorm_Minimum>
  <dialnorm_Minimum_String>-31 dB</dialnorm_Minimum_String>
  <dialnorm_Maximum>-31</dialnorm_Maximum>
  <dialnorm_Maximum_String>-31 dB</dialnorm_Maximum_String>
  <dialnorm_Count>559</dialnorm_Count>
 </extra>
</track>

<track type="Audio" typeorder="2">
 <StreamOrder>2</StreamOrder>
 <ID>3</ID>
 <UniqueID>1226757255</UniqueID>
 <Format>AC-3</Format> 
 <Format_Settings_Endianness>Big</Format_Settings_Endianness>
 <CodecID>A_AC3</CodecID>
 <Duration>7087.808</Duration>
 <BitRate_Mode>CBR</BitRate_Mode>
 <BitRate>640000</BitRate>
 <Channels>6</Channels>
 <ChannelPositions>Front: L C R, Side: L R, LFE</ChannelPositions>
 <ChannelLayout>L C R LFE Ls Rs</ChannelLayout>
 <SamplesPerFrame>1536</SamplesPerFrame>
 <SamplingRate>48000</SamplingRate>
 <SamplingCount>340214784</SamplingCount>
 <FrameRate>31.250</FrameRate>
 <BitDepth>16</BitDepth>
 <Compression_Mode>Lossy</Compression_Mode>
 <Delay>0.000</Delay>
 <Delay_Source>Container</Delay_Source>
 <StreamSize>567024640</StreamSize>
 <StreamSize_Proportion>0.07407</StreamSize_Proportion>
 <Language>en</Language>
 <ServiceKind>CM</ServiceKind>
 <Default>No</Default>
 <Forced>No</Forced>
 <extra>
  <bsid>8</bsid>
  <dialnorm>-31</dialnorm>
  <dialnorm_String>-31 dB</dialnorm_String>
  <acmod>7</acmod>
  <lfeon>1</lfeon>
  <dialnorm_Average>-31</dialnorm_Average>
  <dialnorm_Average_String>-31 dB</dialnorm_Average_String>
  <dialnorm_Minimum>-31</dialnorm_Minimum>
  <dialnorm_Minimum_String>-31 dB</dialnorm_Minimum_String>
  <dialnorm_Maximum>-31</dialnorm_Maximum>
  <dialnorm_Maximum_String>-31 dB</dialnorm_Maximum_String>
  <dialnorm_Count>556</dialnorm_Count>
 </extra>
</track>

</media>
</MediaInfo>

Answer 1

您缺少使用 xmlstarlet 的 -N 参数设置 XML 源的命名空间。因此，以下命令应根据需要设置值:

xmlstarlet -q ed -N mi="https://mediaarea.net/mediainfo" -u "/mi:MediaInfo/mi:media/mi:track[@type='Video']/mi:BitRate" -v "123456 Kb/s" test.xml

它将 @type='video' track 的 BitRate 设置为“123456 Kb/s”。