File: gawk.info,  Node: Action Overview,  Next: Statements,  Prev: Using Shell Variables,  Up: Patterns and Actions

7.3 Actions
===========

An 'awk' program or script consists of a series of rules and function
definitions interspersed.  (Functions are described later.  *Note
User-defined::.)  A rule contains a pattern and an action, either of
which (but not both) may be omitted.  The purpose of the "action" is to
tell 'awk' what to do once a match for the pattern is found.  Thus, in
outline, an 'awk' program generally looks like this:

     [PATTERN]  '{ ACTION }'
      PATTERN  ['{ ACTION }']
     ...
     'function NAME(ARGS) { ... }'
     ...

   An action consists of one or more 'awk' "statements", enclosed in
braces ('{...}').  Each statement specifies one thing to do.  The
statements are separated by newlines or semicolons.  The braces around
an action must be used even if the action contains only one statement,
or if it contains no statements at all.  However, if you omit the action
entirely, omit the braces as well.  An omitted action is equivalent to
'{ print $0 }':

     /foo/  { }     match 'foo', do nothing -- empty action
     /foo/          match 'foo', print the record -- omitted action

   The following types of statements are supported in 'awk':

Expressions
     Call functions or assign values to variables (*note Expressions::).
     Executing this kind of statement simply computes the value of the
     expression.  This is useful when the expression has side effects
     (*note Assignment Ops::).

Control statements
     Specify the control flow of 'awk' programs.  The 'awk' language
     gives you C-like constructs ('if', 'for', 'while', and 'do') as
     well as a few special ones (*note Statements::).

Compound statements
     Enclose one or more statements in braces.  A compound statement is
     used in order to put several statements together in the body of an
     'if', 'while', 'do', or 'for' statement.

Input statements
     Use the 'getline' command (*note Getline::).  Also supplied in
     'awk' are the 'next' statement (*note Next Statement::) and the
     'nextfile' statement (*note Nextfile Statement::).

Output statements
     Such as 'print' and 'printf'.  *Note Printing::.

Deletion statements
     For deleting array elements.  *Note Delete::.