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Info Node: (gawk.info)Expressions

(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.

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