Go forward to Arithmetic Ops.
Go backward to Constants.
Go up to Expressions.
Variables let you give names to values and refer to them later. You
have already seen variables in many of the examples. The name of a
variable must be a sequence of letters, digits and underscores, but it
may not begin with a digit. Case is significant in variable names; `a'
and `A' are distinct variables.
A variable name is a valid expression by itself; it represents the
variable's current value. Variables are given new values with
"assignment operators" and "increment operators". *Note Assignment
Expressions: Assignment Ops.
A few variables have special built-in meanings, such as `FS', the
field separator, and `NF', the number of fields in the current input
record. See Built-in Variables, for a list of them. These
built-in variables can be used and assigned just like all other
variables, but their values are also used or changed automatically by
`awk'. Each built-in variable's name is made entirely of upper case
Variables in `awk' can be assigned either numeric or string values.
By default, variables are initialized to the null string, which is
effectively zero if converted to a number. There is no need to
"initialize" each variable explicitly in `awk', the way you would in C
or most other traditional languages.
- Assignment Options
- Setting variables on the command line
and a summary of command line syntax.
This is an advanced method of input.