(gawk.info)Getting Started


Getting Started with `awk'
**************************

   The basic function of `awk' is to search files for lines (or other
units of text) that contain certain patterns.  When a line matches one
of the patterns, `awk' performs specified actions on that line.  `awk'
keeps processing input lines in this way until it reaches the end of
the input files.

   Programs in `awk' are different from programs in most other
languages, because `awk' programs are "data-driven"; that is, you
describe the data you want to work with and then what to do when you
find it.  Most other languages are "procedural"; you have to describe,
in great detail, every step the program is to take.  When working with
procedural languages, it is usually much harder to clearly describe the
data your program will process.  For this reason, `awk' programs are
often refreshingly easy to write and read.

   When you run `awk', you specify an `awk' "program" that tells `awk'
what to do.  The program consists of a series of "rules".  (It may also
contain "function definitions", an advanced feature that we will ignore
for now.  Note: User-Defined Functions.)  Each rule
specifies one pattern to search for and one action to perform upon
finding the pattern.

   Syntactically, a rule consists of a pattern followed by an action.
The action is enclosed in curly braces to separate it from the pattern.
Newlines usually separate rules.  Therefore, an `awk' program looks
like this:

     PATTERN { ACTION }
     PATTERN { ACTION }
     ...

Running gawk: How to run `gawk' programs; includes
Sample Data Files: Sample data files for use in the `awk'
Very Simple: A very simple example.
Two Rules: A less simple one-line example using two
More Complex: A more complex example.
Statements/Lines: Subdividing or combining statements into
Other Features: Other Features of `awk'.
When: When to use `gawk' and when to use

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