Info Catalog gawk: Preface gawk: Top gawk: Invoking Gawk

gawk: Getting Started

 
 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'
 continues to process 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" (i.e., 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 should 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 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.
· Intro Summary               Summary of the introduction.
 

Info Catalog gawk: Preface gawk: Top gawk: Invoking Gawk