Hi.
You'll need to be more specific. When something works correctly, we can see that it works. If it fails, there could be a number of reasons, and we need to examine the evidence.

If you run my script with the data1 file, does it work? ... cheers, drl

drl,
I don't understand what your data1 file is.
Spin

Or rather:
could you explain precisely the syntax in the script to read the data1 file? Is data1 a filename?

OK, I tried your script with a file named (data1) and it comes close to working. Except the only thing is that the modified text splits into two lines
-------------Do
cument 7 of 9

I double-checked where the newline character is in the replacement portion of my script and it appears to be right where it should be.

Hi.

OK, that sounds like progress. As I did, please post the script and the output, using CODE tags around them to make them readable ... cheers, drl

OK: now I'm trying this again, and for some reason it's failed to work.
Here is the precise script I'm running:
#!/bin/sh
# @(#) s1 Demonstrate sed line split and merge.

set -o nounset
echo " sh version: $BASH_VERSION" >&2
sed --version | head -1

FILE=${1-data1}

echo
echo " Input file:"
nl $FILE

cat >script <<'EOF'
/==Document$/
N
s/==Document\n/==\nDocument/
}
EOF

echo
echo " Output"
sed -f script $FILE |
nl

exit 0
When I run this on data1 (I've taken one of my own text files and renamed it data1 to match the script), it cats the file with numbered lines and then reads this output error:

Output
sed: 1: script: command expected

Hi.

You are missing a curly brace in the script:
should be:
cheers, drl