Xml grep

When working with xml, you'll often want to grep out an element that spans several lines. This can be hacked with awk or perl, but a more elegant solution is to use the parser in libxml2 (which is a requirement when installing apertium, so should be installed on your system already). This lets you use a simple version of XPath expressions to grep out full XML elements.

Examples:

# Specifying the full path and the full pardef name:
$ xmllint --xpath '/dictionary/pardefs/pardef[@n="gen__apos"]' apertium-eo-en.en.dix
<pardef n="gen__apos">
  <e>       <p><l/>          <r/></p></e>
  <e>       <p><l>'</l>         <r><j/>'<s n="gen"/></r></p></e>
</pardef>

# But for dix files, it should be the same if you specify a relative path:
$ xmllint --xpath '//pardef[@n="gen__apos"]' apertium-eo-en.en.dix
<pardef n="gen__apos">
  <e>       <p><l/>          <r/></p></e>
  <e>       <p><l>'</l>         <r><j/>'<s n="gen"/></r></p></e>
</pardef>

# You can also search for substrings by using the 'contains' function:
$ xmllint --xpath '//pardef[contains(@n,"_adj")]' apertium-eo-en.en.dix
<pardef n="expensive__adj">
  <e>       <p><l/>          <r><s n="adj"/></r></p></e>
</pardef>
<pardef n="ca__adj">…
# etc; gives all the adj pardefs