Using sed, Insert a line above or below the pattern?

Question

I need to edit a good number of files, by inserting a line or multiple lines either right below a unique pattern or above it. Please advise on how to do that using sed, awk, perl (or anything else) in a shell. Thanks! Example:

some text
lorem ipsum dolor sit amet
more text

I want to insert consectetur adipiscing elit after lorem ipsum dolor sit amet, so the output file will look like:

some text
lorem ipsum dolor sit amet
consectetur adipiscing elit
more text

Answer 1

To append after the pattern: (-i is for in place replace). line1 and line2 are the lines you want to append(or prepend)

sed -i '/pattern/a \
line1 \
line2' inputfile

Output:

#cat inputfile
 pattern
 line1 line2 

To prepend the lines before:

sed -i '/pattern/i \
line1 \
line2' inputfile

Output:

#cat inputfile
 line1 line2 
 pattern