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14.2.7 Macro Expressions

Macro expressions are used in conditional expansion and loops, which are described in the following sections. A macro expression may use the following operators, listed in descending order of operator precedence:

()

Parentheses override the default operator precedence.

!EQ !NE !GT !LT !GE !LE = ~= <> > < >= <=

Relational operators compare their operands and yield a Boolean result, either ‘0’ for false or ‘1’ for true.

These operators always compare their operands as strings. This can be surprising when the strings are numbers because, e.g., 1 < 1.0 and 10 < 2 both evaluate to ‘1’ (true).

Comparisons are case sensitive, so that a = A evaluates to ‘0’ (false).

!NOT ~

!AND &

!OR |

Logical operators interpret their operands as Boolean values, where quoted or unquoted ‘0’ is false and anything else is true, and yield a Boolean result, either ‘0’ for false or ‘1’ for true.

Macro expressions do not include any arithmetic operators.

An operand in an expression may be a single token (including a macro argument name) or a macro function invocation. Either way, the expression evaluator unquotes the operand, so that 1 = '1' is true.