This option is equivalent to the @include directive, which is used to source a file in the current AWK program. However, it is different from the -f option in two aspects. First, when we use the -i option, the program sourced is not loaded if it has been previously loaded, whereas -f always loads a file. The second difference is this after processing an -i argument, GAWK still expects to find the main source code via the -f option or on the command line:

-i source-file
--include source-file

In the next example, we will use the f1.awk and f2.awk files we created earlier to describe how the -i option works:

$ awk  -i  f1.awk  'NR==5 { print NR,  $0 }'  cars.dat

The output on execution of the given code is:

2 honda           city        2005        60000       3
5 honda           city        2010        33000       6

Now, we are using the -i option to include the f1.awk file inside the -f option to execute f2.awk, as follows:

$ awk  -i  f1.awk   -f   f2.awk    cars.dat

The output on execution of the preceding code is:

2 honda           city        2005        60000       3
4 chevy           beat        2005        33000       2

The next example shows it is mandatory to specify the AWK command or main source file using the -f option for executing a program with the -i option:

$ awk  -i  f1.awk cars.dat

The output on execution of the code is:

awk: cmd. line:1: cars.dat
awk: cmd. line:1:     ^ syntax error