awk Programs
Once you are familiar with awk, you will often type in simple
programs the moment you want to use them. Then you can write the
program as the first argument of the awk command, like this:
awk 'program' input-file1 input-file2 ...
where program consists of a series of patterns and actions, as described earlier.
This command format instructs the shell, or command interpreter,
to start awk and use the program to process records in the
input file(s). There are single quotes around program so that
the shell doesn't interpret any awk characters as special shell
characters. They also cause the shell to treat all of program as
a single argument for awk and allow program to be more
than one line long.
This format is also useful for running short or medium-sized awk
programs from shell scripts, because it avoids the need for a separate
file for the awk program. A self-contained shell script is more
reliable since there are no other files to misplace.
section Useful One Line Programs, presents several short, self-contained programs.
As an interesting side point, the command
awk '/foo/' files ...
is essentially the same as
egrep foo files ...
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