xml xmllint 无法使用 xpath 正确查询
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xmllint failing to properly query with xpath
提问by ailnlv
I'm trying to query an xml file generated by adium. xmlwf says that it's well formed. By using xmllint's debug option i get the following:
我正在尝试查询由 adium 生成的 xml 文件。xmlwf 说它的格式很好。通过使用 xmllint 的调试选项，我得到以下信息：
$ xmllint --debug doc.xml
DOCUMENT
version=1.0
encoding=UTF-8
URL=doc.xml
standalone=true
ELEMENT chat
default namespace href=http://purl.org/net/ulf/ns/0.4-02
ATTRIBUTE account
TEXT
[email protected]
ATTRIBUTE service
TEXT compact
content=MSN
TEXT compact
content=
ELEMENT event
ATTRIBUTE type
Everything seems to parse just fine. However, when I try to query even the simplest things, I don't get anything:
一切似乎都解析得很好。但是，当我尝试查询即使是最简单的事情时，也没有得到任何信息：
$ xmllint --xpath '/chat' doc.xml
XPath set is empty
What's happening? Running that exact same query using xpath returns the correct results (however with no newline between results). Am I doing something wrong or is xmllint just not working properly?
发生了什么？使用 xpath 运行完全相同的查询会返回正确的结果（但是结果之间没有换行符）。我做错了什么还是 xmllint 工作不正常？
Here's a shorter, anonymized version of the xml that shows the same behavior:
这是 xml 的一个较短的匿名版本，它显示了相同的行为：
<?xml version="1.0" encoding="UTF-8" ?>
<chat xmlns="http://purl.org/net/ulf/ns/0.4-02" account="[email protected]" service="MSN">
<event type="windowOpened" sender="[email protected]" time="2011-11-22T00:34:43-03:00"></event>
<message sender="[email protected]" time="2011-11-22T00:34:43-03:00" alias="foo"><div><span style="color: #000000; font-family: Helvetica; font-size: 12pt;">hi</span></div></message>
</chat>
回答by Daniel Haley
I don't use xmllint, but I think the reason your XPath isn't working is because your doc.xml file is using a default namespace (http://purl.org/net/ulf/ns/0.4-02).
我不使用 xmllint，但我认为您的 XPath 无法正常工作的原因是您的 doc.xml 文件使用了默认命名空间 ( http://purl.org/net/ulf/ns/0.4-02)。
From what I can see, you have 2 options.
据我所知，您有两个选择。
A.Use xmllint in shell mode and declare the namespace with a prefix. You can then use that prefix in your XPath.
A.在 shell 模式下使用 xmllint 并使用前缀声明命名空间。然后，您可以在 XPath 中使用该前缀。
xmllint --shell doc.xml
/ > setns x=http://purl.org/net/ulf/ns/0.4-02
/ > xpath /x:chatB.Use local-name()to match element names.
B.使用local-name()匹配的元素名称。
xmllint --xpath /*[local-name()='chat']You may also want to use namespace-uri()='http://purl.org/net/ulf/ns/0.4-02'along with local-name()so you are sure to return exactly what you are intending to return.
您可能还想namespace-uri()='http://purl.org/net/ulf/ns/0.4-02'与 with一起使用，local-name()以便确保准确返回您打算返回的内容。
回答by codesniffer
I realize this question is very old now, but in case it helps someone...
我意识到这个问题现在已经很老了，但万一它对某人有帮助......
Had the same problem and it was due to the XML having a namespace (and sometimes it was duplicated in various places in the XML). Found it easiest to just remove the namespace before using xmllint:
有同样的问题，这是由于 XML 具有命名空间（有时它在 XML 的不同位置重复）。发现在使用 xmllint 之前删除命名空间最简单：
sed -e 's/xmlns=".*"//g' file.xml | xmllint --xpath "..." -
In my case the XML was UTF-16 so I had to convert to UTF-8 first (for sed):
在我的情况下，XML 是 UTF-16，所以我必须先转换为 UTF-8（对于 sed）：
iconv -f utf16 -t utf8 file.xml | sed -e 's/encoding="UTF-16"?>/encoding="UTF-8"?>/' | sed -e 's/xmlns=".*"//g' | xmllint --xpath "..." -
