XMLStarlet和RSS

Question

我似乎无法通过xmlstarlet实现这个基本的xslt查询。

我肯定我遗漏了一些显而易见的东西，但在我的生活中，我无法理解这个语法，所以请有人指点我。

XML Starlet命令：

xml sel -t -m "//rdf:RDF/item" -v link -v description -v link ./sss.rdf

sss.rdf：

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns="http://purl.org/rss/1.0/" xmlns:admin="http://webns.net/mvcb/" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:dcterms="http://purl.org/dc/terms/" xmlns:ev="http://purl.org/rss/1.0/modules/event/" xmlns:syn="http://purl.org/rss/1.0/modules/syndication/" xmlns:taxo="http://purl.org/rss/1.0/modules/taxonomy/">
    <channel rdf:about="http://baltimore.craigslist.org/search/sss?catAbb=sss&amp;amp;format=rss&amp;amp;maxAsk=150&amp;amp;minAsk=50&amp;amp;query=ipod%20touch%205g&amp;amp;srchType=A">
        <title>craigslist baltimore | all for sale / wanted search "ipod touch 5g"</title>
        <link>http://baltimore.craigslist.org/search/sss?catAbb=sss&amp;amp;maxAsk=150&amp;amp;minAsk=50&amp;amp;query=ipod%20touch%205g&amp;amp;srchType=A</link>
        <description />
        <dc:language>en-us</dc:language>
        <dc:rights>&amp;copy; 2013 craigslist</dc:rights>
        <dc:publisher>robot@craigslist.org</dc:publisher>
        <dc:creator>robot@craigslist.org</dc:creator>
        <dc:source>http://baltimore.craigslist.org/search/sss?catAbb=sss&amp;amp;format=rss&amp;amp;maxAsk=150&amp;amp;minAsk=50&amp;amp;query=ipod%20touch%205g&amp;amp;srchType=A</dc:source>
        <dc:title>craigslist baltimore | all for sale / wanted search "ipod touch 5g"</dc:title>
        <dc:type>Collection</dc:type>
        <syn:updateBase>2013-09-20T09:23:41-07:00</syn:updateBase>
        <syn:updateFrequency>1</syn:updateFrequency>
        <syn:updatePeriod>hourly</syn:updatePeriod>
        <items>
            <rdf:Seq>
                <rdf:li rdf:resource="http://baltimore.craigslist.org/ele/4039527375.html" />
            </rdf:Seq>
        </items>
    </channel>
    <item rdf:about="http://baltimore.craigslist.org/ele/4039527375.html">
        <title><![CDATA[Unlocked Optimus Lg Phone (Baltimore) $150]]></title>
        <link>http://baltimore.craigslist.org/ele/4039527375.html</link>
        <description>OR WE CAN HAVE A SWAP FOR AN IPOD TOUCH 5g<![CDATA[
&#9679;Optimus Lg Phone For Sale At 150.00 The Original Price Was $180.00
&#9679;It Does Not Include The Charger, But You Can Find It At Walmart For $4.00
&#9679;The Phone Was Only Used For 2-3 Months
&# [...]]]></description>
        <dc:date>2013-09-01T10:14:06-07:00</dc:date>
        <dc:language>en-us</dc:language>
        <dc:rights>&amp;copy; 2013 craigslist</dc:rights>
        <dc:source>http://baltimore.craigslist.org/ele/4039527375.html</dc:source>
        <dc:title><![CDATA[Unlocked Optimus Lg Phone (Baltimore) $150]]></dc:title>
        <dc:type>text</dc:type>
        <dcterms:issued>2013-09-01T10:14:06-07:00</dcterms:issued>
    </item>
</rdf:RDF>

我想要的输出：

Unlocked Optimus Lg Phone (Baltimore) $150
OR WE CAN HAVE A SWAP FOR AN IPOD TOUCH 5g
    ●Optimus Lg Phone For Sale At 150.00 The Original Price Was $180.00
    ●It Does Not Include The Charger, But You Can Find It At Walmart For $4.00
    ●The Phone Was Only Used For 2-3 Months
    &# [...]
http://baltimore.craigslist.org/ele/4039527375.html

Answer 1

这个XmlStarlet命令：

xml sel -N purl="http://purl.org/rss/1.0/" -t -m "//rdf:RDF/purl:item" -v purl:title -n -v purl:description -n -v purl:link -n ./sss.rdf

产生所需的输出：

Unlocked Optimus Lg Phone (Baltimore) $150
OR WE CAN HAVE A SWAP FOR AN IPOD TOUCH 5g
●Optimus Lg Phone For Sale At 150.00 The Original Price Was $180.00
●It Does Not Include The Charger, But You Can Find It At Walmart For $4.00
●The Phone Was Only Used For 2-3 Months
&# [...]
http://baltimore.craigslist.org/ele/4039527375.html

解释：

关键是要注意输入文档有一个默认名称空间，这将导致item、title、description和link位于http://purl.org/rss/1.0/名称空间中。定义-N purl="http://purl.org/rss/1.0/"允许我们在XPaths中指定这些元素时使用purl前缀。没有purl名称空间前缀，XPaths就不匹配。