I've found xmlstarlet to be pretty good at this sort of thing.

http://xmlstar.sourceforge.net/

Should be available in most distro repositories, too. An introductory tutorial is here:

http://www.ibm.com/developerworks/library/x-starlet.html

Some promising tools:

• nokogiri: parsing HTML/XML DOMs in ruby using XPath & CSS selectors

• hpricot: deprecated

• fxgrep: Uses its own XPath-like syntax to query documents. Written in SML, so installation may be difficult.

• LT XML: XML toolkit derived from SGML tools, including sggrep, sgsort, xmlnorm and others. Uses its own query syntax. The documentation is very formal. Written in C. LT XML 2 claims support of XPath, XInclude and other W3C standards.

• xmlgrep2: simple and powerful searching with XPath. Written in Perl using XML::LibXML and libxml2.

• XQSharp: Supports XQuery, the extension to XPath. Written for the .NET Framework.

• xml-coreutils: Laird Breyer's toolkit equivalent to GNU coreutils. Discussed in an interesting essay on what the ideal toolkit should include.

• xmldiff: Simple tool for comparing two xml files.

• xmltk: doesn't seem to have package in debian, ubuntu, fedora, or macports, hasn't had a release since 2007, and uses non-portable build automation.

xml-coreutils seems the best documented and most UNIX-oriented.

To Joseph Holsten's excellent list, I add the xpath command-line script which comes with Perl library XML::XPath. A great way to extract information from XML files:

 xpath -q -e '/entry[@xml:lang="fr"]' *xml

Depends on exactly what you want to do.

XSLT may be the way to go, but there is a learning curve. Try xsltproc and note that you can hand in parameters.

D. Bohdan maintains an open source GitHub repo that keeps a list of command line tools for structured text tools, there a section for XML/HTML tools:

https://github.com/dbohdan/structured-text-tools#xml-html

XQuery might be a good solution. It is (relatively) easy to learn and is a W3C standard.

I would recommend XQSharp for a command line processor.

Grep Equivalent

You can define a bash function, say "xp" ("xpath") that wraps some python3 code. To use it you need to install python3 and python-lxml. Benefits:

1. regex matching which you lack in e.g. xmllint.
2. Use as a filter (in a pipe) on the commandline

It's easy and powerful to use like this:

xmldoc=$(cat <<EOF
<?xml version="1.0" encoding="utf-8"?>
<job xmlns="http://www.sample.com/">programming</job>
EOF
)
selection='//*[namespace-uri()="http://www.sample.com/" and local-name()="job" and re:test(.,"^pro.*ing$")]/text()'
echo "$xmldoc" | xp "$selection"
# prints programming

xp() looks something like this:

xp()
{ 
local selection="$1";
local xmldoc;
if ! [[ -t 0 ]]; then
    read -rd '' xmldoc;
else
    xmldoc="$2";
fi;
python3 <(printf '%b' "from lxml.html import tostring\nfrom lxml import etree\nfrom sys import stdin\nregexpNS = \"http://exslt.org/regular-expressions\"\ntree = etree.parse(stdin)\nfor e in tree.xpath('""$selection""', namespaces={'re':regexpNS}):\n  if isinstance(e, str):\n    print(e)\n  else:\n    print(tostring(e).decode('UTF-8'))") <<< "$xmldoc"
}

Sed Equivalent

Consider using xq which gives you the full power of the jq "programming language". If you have python-pip installed, you can install xq with pip install yq, then in below example we are replacing "Keep Accounts" with "Keep Accounts 2":

xmldoc=$(cat <<'EOF'
<resources>
    <string name="app_name">Keep Accounts</string>
    <string name="login">"login"</string>
    <string name="login_password">"password："</string>
    <string name="login_account_hint">input to login</string>
    <string name="login_password_hint">input your password</string>
    <string name="login_fail">login failed</string>
</resources>
EOF
)
echo "$xmldoc" | xq '.resources.string = ([.resources.string[]|select(."#text" == "Keep Accounts") ."#text" = "Keep Accounts 2"])' -x

JEdit has a plugin called "XQuery" which provides querying functionality for XML documents.

Not quite the command line, but it works!