Sometimes your awk programs can be very long. In this case it is
more convenient to put the program into a separate file. To tell
awk to use that file for its program, you type:
awk -f source-file input-file1 input-file2 ...
The `-f' instructs the awk utility to get the awk program
from the file source-file. Any file name can be used for
source-file. For example, you could put the program:
BEGIN { print "Don't Panic!" }
into the file `advice'. Then this command:
awk -f advice
does the same thing as this one:
awk "BEGIN { print \"Don't Panic!\" }"
which was explained earlier (see section Running awk without Input Files).
Note that you don't usually need single quotes around the file name that you
specify with `-f', because most file names don't contain any of the shell's
special characters. Notice that in `advice', the awk
program did not have single quotes around it. The quotes are only needed
for programs that are provided on the awk command line.
If you want to identify your awk program files clearly as such,
you can add the extension `.awk' to the file name. This doesn't
affect the execution of the awk program, but it does make
"housekeeping" easier.
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