The shell allows arithmetic expressions to be evaluated, as one of the shell
expansions or by the
Evaluation is done in long integers with no check for overflow, though division
by 0 is trapped and flagged as an error. The operators and their precedence
and associativity are the same as in the C language.
The following list of operators is grouped into levels of equal-precedence operators. The levels are listed in order of decreasing precedence.
* / %
<= >= < >
expr ? expr : expr
= *= /= %= += -= <<= >>= &= ^= |=
expr1 , expr2
Shell variables are allowed as operands; parameter expansion is performed before the expression is evaluated. Within an expression, shell variables may also be referenced by name without using the parameter expansion syntax. The value of a variable is evaluated as an arithmetic expression when it is referenced. A shell variable need not have its integer attribute turned on to be used in an expression.
Constants with a leading 0 are interpreted as octal numbers.
A leading `0x' or `0X' denotes hexadecimal.
Otherwise, numbers take the form [base
where base is a decimal number between 2 and 64 representing the
arithmetic base, and n is a number in that base. If base
is omitted, then base 10 is used. The digits greater than 9 are represented
by the lowercase letters, the uppercase letters, `_', and `@',
in that order. If base is less than or equal to 36, lowercase and
uppercase letters may be used interchangably to represent numbers between 10
Operators are evaluated in order of precedence. Sub-expressions in parentheses are evaluated first and may override the precedence rules above.
NIST Digital Library of Mathematical Functions
Windows equivalent command: SET /A - Display, set, or remove Windows environment variables