SERIES : awk#1 Begin and End

Awk comes with inbuilt loop. It performs the given operations for each line in the input file provided they are not qualified by "BEGIN" or "END".

cat notxt
<-- empty file -->

cat sometxt
monkey goes to market

awk '{print "Hello World!"}' notxt
<--no ouput-->

awk 'BEGIN {print "Hello World!"} {print} END {print "Good bye!"}' notxt
Hello World!
Good bye!

awk 'BEGIN {print "Hello World!"} {print} END {print "Good bye!"}' sometxt
Hello World!
monkey goes to market
Good bye!

ex#1.
Since notxt is empty; awk doesn't iterate and no output is printed.

ex#2.
although notxt is empty; BEGIN and END statements are still executed and output produced for those commands.