Here is synopsis for 'xml fo' command:

XMLStarlet Toolkit: Format XML document
Usage: xml fo [<options>] <xml-file>
where <options> are
   -n or --noindent            - do not indent
   -t or --indent-tab          - indent output with tabulation
   -s or --indent-spaces <num> - indent output with <num> spaces
   -o or --omit-decl           - omit xml declaration <?xml version="1.0"?>
   -R or --recover             - try to recover what is parsable
   -D or --dropdtd             - remove the DOCTYPE of the input docs
   -C or --nocdata             - replace cdata section with text nodes
   -N or --nsclean             - remove redundant namespace declarations
   -e or --encode <encoding>   - output in the given encoding (utf-8, unicode...)
   -H or --html                - input is HTML
   -h or --help                - print help

XMLStarlet is a command line toolkit to query/edit/check/transform
XML documents (for more information see http://xmlstar.sourceforge.net/)

EXAMPLE

# Format XML document disabling indent
cat xml/tab-obj.xml | xml fo --noindent 

Output:

<xml>
<table>
<rec id="1">
<numField>123</numField>
<stringField>String Value</stringField>
<object name="Obj1">
<property name="size">10</property>
<property name="type">Data</property>
</object>
</rec>
<rec id="2">
<numField>346</numField>
<stringField>Text Value</stringField>
</rec>
<rec id="3">
<numField>-23</numField>
<stringField>stringValue</stringField>
</rec>
</table>
</xml>

EXAMPLE

# Recover malformed XML document
xml fo -R xml/malformed.xml 2>/dev/null

Input:

<test_output>
   <test_name>foo</testname>
   <subtest>...</subtest>
</test_output>

Output:

<test_output>
  <test_name>foo</test_name>
  <subtest>...</subtest>
</test_output>