| The let command performs arithmetic. ksh88 and Bash are restricted to integer arithmetic. ksh93 can do floating-point arithmetic as well. Both shells provide a way to substitute arithmetic values (for use as command arguments or in variables); base conversion is also possible: $(( expr )) | Use the value of the enclosed arithmetic expression. | B#n | Interpret integer n in numeric base B. For example, 8#100 specifies the octal equivalent of decimal 64. |
4.6.1. Operators The shells use arithmetic operators from the C programming language, in decreasing order of precedence. ksh88 does not support the ++, --, unary +, ?:, comma, or ** operators. Early versions of ksh93 do not have **. Operator | Description |
|---|
++ -- | Auto-increment and auto-decrement, both prefix and postfix. | + - ! ~ | Unary plus and minus, logical negation and binary inversion (one's complement). | ** | Exponentiation.a | * / % | Multiplication; division; modulus (remainder). | + - | Addition; subtraction. | << >> | Bitwise left shift; bitwise right shift. | < <= > >= | Less than; less than or equal to; greater than; greater than or equal to. | == != | Equality; inequality (both evaluated left to right). | & | Bitwise AND. | ^ | Bitwise exclusive OR. | | | Bitwise OR. | && | Logical AND (short-circuit). | || | Logical OR (short-circuit). | ?: | Inline conditional evaluation. | = += -= | | *= /= %= | | <<= >>= | Assignment. | &= ^= |= | | , | Sequential expression evaluation. | a In ksh93, the ** operator is right-associative. In bash versions prior to 3.1, it is left-associative. It will be changed to right-associative starting with version 3.1. |
4.6.2. Built-in Mathematical Functions (ksh93 Only) ksh93 provides access to the standard set of mathematical functions. They are called using C function call syntax. Name | Function | Name | Function |
|---|
abs | Absolute value | hypot | Euclidean distance | acos | Arc cosine | int | Integer part of floating-point number | asin | Arc sine | log | Natural logarithm | atan | Arc tangent | pow | Exponentiation (x y) | atan2 | Arc tangent of two values | sin | Sine | cos | Cosine | sinh | Hyperbolic sine | cosh | Hyperbolic cosine | sqrt | Square root | exp | Exponential (e x) | tan | Tangent | fmod | Floating-point remainder | tanh | Hyperbolic tangent |
4.6.3. Examples let "count=0" "i = i + 1" Assign i and count let "num % 2" Test for an even number (( percent >= 0 && percent <= 100 )) Test the range of a value
See the let entry in the later section "Built-in Commands (Bash and Korn Shells)" for more information and examples. |
