make sample.xml of this format, this is one entry

<student>
<name>name</name>
<usn>usn</usn>
<dept>dept</dept>
</student>
<dept>
<name>name</name>
<id>id</id>
<total>total</total>


1) sed "/dept/,/\dept/d" sample.xml >student.xml
2) sed "/dept/,/\dept/s/name/deptname/g" sample.xml >dept.xml
3) sed -n '/usn/{s/.*<usn>//;s/<\/usn.*//;p;}' sample.xml > usn.txt