(gawk.info.gz) Getting Started

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 1 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 read and write.
 
    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.   User-defined.)  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 }
      ...
 

Menu

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