xmlstarlet returns 1 with empty value - exit-code

Question

I'm tring use xmlstarlet for parsing this file.xml:
<resultset>
<row>
<field name="b">2</field>
<field name="c"></field>
</row>
</resultset>
With first field evrithing is ok
$ xmlstarlet sel -t -v "resultset/row[1]/field[1]" file.xml
2
$ echo $?
0
But with second field xmlstarlet returns 1
$ xmlstarlet sel -t -v "resultset/row[1]/field[1]" file.xml
$ echo $?
1
In my case empty fields are normal. I want to parse its without xmlstarlet error.
UPDATE:
the same behavior with field[#name="b"]:
$ xmlstarlet sel -t -v 'resultset/row/field[#name="b"]' file.xml
2
$ echo $?
0
and
$ xmlstarlet sel -t -v 'resultset/row/field[#name="c"]' file.xml
$ echo $?
1
i want to distinguish the second case from the real error
UPDATE 2: The MAIN PROBLEM is:
If i try select [#name="c"] and [#name="not_exits"] xmlstarlet returns the SAME exit code 1.
But file.xml has field name 'c', and does not have field with name 'not_exist'.
I want xmlstarlet prints empti string and return exit code 0 when file.xml contains empty field with the given name,
and returns non-null exit code when file.xml does not contain field with the given name at all.

Answer 1

Try changing you xpath expressions to
resultset/row/field[#name="b"]
and
resultset/row/field[#name="c"]
and see if it works.
Edit:
I'm not sure what exactly you are echoing in your question, but if we assume your xml is in a file called file.xml, these expressions work with no errors:
xmlstarlet sel -T -t -m "resultset/row/field[#name='b']" -v . --nl file.xml
and
xmlstarlet sel -T -t -m "resultset/row/field[#name='c']" -v . --nl file.xml

Answer 2

I think -n or --nl does the trick to exit with 0 when there is empty match.
Together with -m ... -v . seems to do what OP wants.
# Empty match
$ echo "<field name=\"c\"></field>" | xmlstarlet sel -t -m "field[#name='c']" -v . --nl
$ echo "${PIPESTATUS[#]}"
0 0
# No match
$ echo "<field name=\"c\"></field>" | xmlstarlet sel -t -m "field[#name='non_existent']" -v . --nl
$ echo "${PIPESTATUS[#]}"
0 1
# Non-empty match
$ echo "<field name=\"c\">xyz</field>" | xmlstarlet sel -t -m "field[#name='c']" -v . --nl
xyz
$ echo "${PIPESTATUS[#]}"
0 0
Notes
This outputs non-empty string. For me it is not a problem, as I filter results later anyway.