z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

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awk
If two expressions are not separated by an operator, awk concatenates their string
values.
The tilde operator ~ yields 1 (true) if the regular expression on the right side
matches the string on the left side. The operator !~ yields 1 when the right side has
no match on the left. To illustrate:
$2 ~ /[0-9]/
selects any line where the second field contains at least one digit. awk interprets
any string or variable on the right side of ~ or !~ as a dynamic regular expression.
The relational operators are =, ==, and !=. When both operands in a
comparison are numeric, or if one is numeric and the other is not initialized, awk
compares their values numerically; otherwise, it compares them as strings. An
operator is considered to be numeric if it consists of any of the following:
v An integer or floating-point number
v A field, FILENAME, ARGV array element, or ENVIRON array element that looks
like a number
v A variable created by a command-line assignment that looks like a number
v Input from a getline() function that looks like a number
v An array element created by the split() function that looks like a number
v A variable assignment from another number variable that looks like a number
The Boolean operators are || (or), && (and), and ! (not). awk uses short-circuit
evaluation when evaluating expressions. With an && expression, if the first operator
is false, the entire expression is false and it is not necessary to evaluate the second
operator. With an || expression, a similar situation exists if the first operator is true.
You can assign values to a variable with:
var = expr
If op is a binary arithmetic operator, var op= expr is equivalent to var = var op expr,
except that var is evaluated only once.
See Table 2 for the precedence rules of the operators.
Table 2. The Order of Operations for awk
Operators Order of operations
(A) Grouping
$i V[a] Field, array element
V++ V-- ++V --V Increment, decrement
A^B Exponentiation
+A -A !A Unary plus, unary minus, logical NOT
A*B A/B A%B Multiplication, division, remainder
A+B A-B Addition, subtraction
A B String concatenation
AB A=B A!=B A==B Comparisons
A~B A!~B Regular expression matching
A in V Array membership
A && B Logical AND
36 z/OS V1R9.0 UNIX System Services Command Reference