Arithmetic Expressions
The let command performs integer arithmetic. bash provides a way to substitute integer values (for use as command arguments or in variables); base conversion is also possible:
| Expression | Meaning |
|---|---|
(( expr))
| Use the value of the enclosed arithmetic expression. |
Operators
bash uses arithmetic operators from the C developing language; the following list is in decreasing order of precedence. Use parentheses to override precedence.
| Operator | Meaning |
|---|---|
| - | Unary minus |
| ! ~ | Logical negation; binary inversion (one's complement) |
| * / % | Multiplication; division; modulus (remainder) |
| + - | Addition; subtraction |
| << >> | Bitwise left shift; bitwise right shift |
| <= >= | Less than or equal to; greater than or equal to |
| < > | Less than; greater than |
| == != | Equality; inequality (both evaluated left to right) |
| & | Bitwise AND |
| ^ | Bitwise exclusive OR |
| | | Bitwise OR |
| && | Logical AND |
| || | Logical OR |
| = | Assign value. |
| += -= | Reassign after addition/subtraction |
| *= /= %= | Reassign after multiplication/division/remainder |
| &= ^= |= | Reassign after bitwise AND/XOR/OR |
| <<= >>= | Reassign after bitwise shift left/right |
Examples
See the let built-in command for more information and examples.
let "count=0" "i = i + 1"Assign i and countlet "num % 2"Test for an even number