How to verify whether a xml file is valid in sh or bash?

Question

How to verify whether a XML file is valid in sh (preferably) or bash?

I have a file that often get corrupted and needs to be replaced while I take my time to investigate the underlying issue.

Is there any easy way of performing this task with sh or bash?

Answer 1

Not directly with bash, but xmllint is fairly widely available.

xmllint --format "${xmlfile}"

This will exit with non-zero status (hint: $? in bash gets you the exit code of the last command) if the XML file is invalid.

Answer 2

XMLStarlet has a validate subcommand. At its simplest, to check for well-formedness:

xmlstarlet val "$filename"

To validate against a DTD:

xmlstarlet val -d "$dtd_filename" "$xml_filename"

To validate against an XSD schema:

xmlstarlet val -s "$xsd_filename" "$xml_filename"

To validate against a RelaxNG schema:

xmlstarlet val -r "$rng_filename" "$xml_filename"

This isn't built into bash -- bash has no built-in XML parser, and validation cannot be performed without one -- but it is widely packaged for modern OS distributions.

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XMLStarlet also has subcommands for extracting information from XML files, editing XML files, etc. If you're going to be working with XML from shell scripts, its use is well-advised.