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(gawk.info)Expressions

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Expressions
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   Expressions are the basic building blocks of `awk' patterns and
actions.  An expression evaluates to a value that you can print, test,
or pass to a function.  Additionally, an expression can assign a new
value to a variable or a field by using an assignment operator.

   An expression can serve as a pattern or action statement on its own.
Most other kinds of statements contain one or more expressions that
specify the data on which to operate.  As in other languages,
expressions in `awk' include variables, array references, constants,
and function calls, as well as combinations of these with various
operators.

Constants

String, numeric and regexp constants.

Using Constant Regexps

When and how to use a regexp constant.

Variables

Variables give names to values for later use.

Conversion

The conversion of strings to numbers and vice

versa.

Arithmetic Ops

Arithmetic operations (`+', `-',

etc.)

Concatenation

Concatenating strings.

Assignment Ops

Changing the value of a variable or a field.

Increment Ops

Incrementing the numeric value of a variable.

Truth Values

What is ``true'' and what is ``false''.

Typing and Comparison

How variables acquire types and how this

affects comparison of numbers and strings with `<', etc.

Boolean Ops

Combining comparison expressions using boolean

operators `||' (``or''), `&&' (``and'') and `!' (``not'').

Conditional Exp

Conditional expressions select between two

subexpressions under control of a third subexpression.

Function Calls

A function call is an expression.

Precedence

How various operators nest.