The q command is used for quitting the sed processing without proceeding to the next line:
$ cat shopping.txt
The output will be as follows:
Product Quantity Unit_Price Total_Cost Apple 2 3 6 Orange 2 .8 1.6 Papaya 2 1.5 3 Chicken 3 5 15 Cashew 1 10 10
Here is an example:
$ sed '3q' shopping.txt
The output will be as follows:
Product Quantity Unit_Price Total_Cost Apple 2 3 6 Orange 2 .8 1.6
In this example, after printing the first to third lines, sed quits further processing.