Shell Programming and Scripting

12345
<script>------------------------</script>
23456<script>-----------</script><script>
-----------------------------------------
--------------------------------</script>
<script>----------------</script><script>
-----------------------------------------
---------------------------</script>34567
4<script>--</script>567<script></script>8
56<script>-------------------</script>789

12345
23456
34567
45678
56789

#n

:top
/<script>/ {
        # Change the first <script> in the line to \n.
        # We can be certain that there will not be a newline in the
        # initial pattern space, so this is unambiguous.
        s//\
/
        # If the closing </script> is on the same line, change it also
        # to \n and delete everything in between, newlines inclusive.
        # If the result in an empty line, print nothing.
        /<\/script>/ {
                s//\
/
                s/\n.*\n//
                b empty?
        }

        # The </script> element is not on the same line as its <script>.
        # Before moving on in search of it, delete from the newline to the
        # end of line.  Print only if the line is not empty.
        s/\n.*//
        /./p

        # Discard lines until closing </script> is found.
        :next
        n
        /<\/script>/! b next

        # Change </script> to \n and delete preceding text.
        s//\
/
        s/.*\n//

        :empty?
        # If the line has been left empty, do not print a blank line.
        /./!d

        # In case there's another <script> element later in the line.
        b top
}
p

$ sed -f descriptinator.sed testdata 
12345
23456
34567
45678
56789