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One-shot Throw-away `awk' Programs
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Once you are familiar with `awk', you will often type simple
programs at 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 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.