There are several ways to run an awk program. If the program is short, it is easiest to include it in the command that runs awk, like this:
awk 'program' input-file1 input-file2 ...
When the program is long, it is usually more convenient to put it in a file and run it with a command like this:
awk -f program-file input-file1 input-file2 ...
This section discusses both mechanisms, along with several variations of each.