Sed one-liner

sed.as

Remove leading and trailing whitespace
# sed  's/^[ \t]*//;s/[ \t]*$//' filename

Replace newline (\n) with ",," (imperfect)
# sed ':a;N;$!ba;s/\n/,/g' filename

simple replace ",," with newline (\n)
# sed 's/,,/\n/g' filename

prepend "##" to each line
# sed 's/^/##/' filename


** more sources **
* http://sed.sourceforge.net/sed1line.txt
* http://www-rohan.sdsu.edu/doc/sed.html