XML处理工具xmlint
一、简介
xmllint其实是由一个叫libxml2的c语言库函数实现的一个小工具，因此效率比较高，对不同系统的支持度也很好，功能也比较全。他一般属于libxml2-utils这个软件包，因此类似与sudo 的命令就可以安装。
二、安装
APT YUM（Ubuntu/Debian ）
apt install -y libxml2-utils
yum install -y libxml2-utils
Brew（MacOS）
brew install xmlstarlet
三、命令详解
1、命令格式
Usage : xmllint [options] XMLfiles ...
Parse the XML files and output the result of the parsing
--version : display the version of the XML library used
--debug : dump a debug tree of the in-memory document
--shell : run a navigating shell
--debugent : debug the entities defined in the document
--copy : used to test the internal copy implementation
--recover : output what was parsable on broken XML documents
--huge : remove any internal arbitrary parser limits
--noent : substitute entity references by their value
--noenc : ignore any encoding specified inside the document
--noout : don't output the result tree
--path 'paths': provide a set of paths for resources
--load-trace : print trace of all external entities loaded
--nonet : refuse to fetch DTDs or entities over network
--nocompact : do not generate compact text nodes
--htmlout : output results as HTML
--nowrap : do not put HTML doc wrapper
--valid : validate the document in addition to std well-formed check
--postvalid : do a posteriori validation, i.e after parsing
--dtdvalid URL : do a posteriori validation against a given DTD
--dtdvalidfpi FPI : same but name the DTD with a Public Identifier
--timing : print some timings
--output file or -o file: save to a given file
--repeat : repeat 100 times, for timing or profiling
--insert : ad-hoc test for valid insertions
--compress : turn on gzip compression of output
--html : use the HTML parser
--xmlout : force to use the XML serializer when using --html
--nodefdtd : do not default HTML doctype
--push : use the push mode of the parser
--pushsmall : use the push mode of the parser using tiny increments
--memory : parse from memory
--maxmem nbbytes : limits memory allocation to nbbytes bytes
--nowarning : do not emit warnings from parser/validator
--noblanks : drop (ignorable?) blanks spaces
--nocdata : replace cdata section with text nodes
--format : reformat/reindent the output
--encode encoding : output in the given encoding
--dropdtd : remove the DOCTYPE of the input docs
--pretty STYLE : pretty-print in a particular style
0 Do not pretty print
1 Format the XML content, as --format
2 Add whitespace inside tags, preserving content
--c14n : save in W3C canonical format v1.0 (with comments)
--c14n11 : save in W3C canonical format v1.1 (with comments)
--exc-c14n : save in W3C exclusive canonical format (with comments)
--nsclean : remove redundant namespace declarations
--testIO : test user I/O support
--catalogs : use SGML catalogs from $SGML_CATALOG_FILES
otherwise XML Catalogs starting from
file:///etc/xml/catalog are activated by default
--nocatalogs: deactivate all catalogs
--auto : generate a small doc on the fly
--xinclude : do XInclude processing
--noxincludenode : same but do not generate XInclude nodes
--nofixup-base-uris : do not fixup xml:base uris
--loaddtd : fetch external DTD
--dtdattr : loaddtd + populate the tree with inherited attributes
--stream : use the streaming interface to process very large files
--walker : create a reader and walk though the resulting doc
--pattern pattern_value : test the pattern support
--chkregister : verify the node registration code
--relaxng schema : do RelaxNG validation against the schema
--schema schema : do validation against the WXS schema
--schematron schema : do validation against a schematron
--sax1: use the old SAX1 interfaces for processing
--sax: do not build a tree but work just at the SAX level
--oldxml10: use XML-1.0 parsing rules before the 5th edition
--xpath expr: evaluate the XPath expression, imply --noout
2、从标准输入输出管道传递处理XML内容
# 从标准输出管道传递
cat settings.xml | xmllint --foramt -
# 从标准输入管道传递
xmllint --html --xpath '/html/body/h1[1]' - <<EOF
<BODY>
<H1>Dublin</H1>
EOF
3、输出控制
# 压缩输出
xmllint --noblanks settings.xml > settings-noblank.xml
# 格式化输出
xmllint --format settings.xml > settings-format.xml
4、语法schema校验
xmllint --schema settings-1.0.0.xsd settings.xml
# xsd文件可以在XML的命名空间中找到下载链接
# 语法校验成功后会输出"validates"，不成功会输出"fails to validate"
# 如果要求只输出校验结果不显示XML内容，可加--noout参数
5、带命名空间的XML查询
例如Maven的settings.xml或pom.xml文件都自带了命名空间。例如：
<?xml version="1.0" encoding="UTF-8"?>
xmllint --xpath "/*[local-name()='settings']" settings.xml
四、XML处理
以Maven默认的settings.xml为例
1、查询
xmllint --xpath '//mirror/url' settings.xml