Q: How do I insert a text line at row 3 in file "test" using sed?
A: The below inserts a new line at row 3 with the string "sometext" in a file called "test.txt"
# sed -i '3isometext' test.txt
A: The below inserts a new line at row 3 with the string "sometext" in a file called "test.txt"
# sed -i '3isometext' test.txt