6.6. Arithmetic Expressions 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. Expression | Meaning |
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$(( 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. |
6.6.1. Operators The shells use arithmetic operators from the C programming language; the following table listing is in decreasing order of precedence. ksh88 does not support the ++, --, unary +, ?:, comma or ** operators. Early versions of ksh93 do not have **. Operator | Operator |
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++ -- | 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.
6.6.2. 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 |
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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 (xy) | atan2 | Arc tangent of two variables | sin | Sine | cos | Cosine | sinh | Hyperbolic sine | cosh | Hyperbolic cosine | sqrt | Square root | exp | Exponential (ex) | tan | Tangent | fmod | Floating-point remainder | tanh | Hyperbolic tangent |
6.6.3. Examples See the let command for more information and 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
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