Linux command
double-parenthesis 命令
文本
复制后可按需替换文件名、目录或参数。
常用示例
Arithmetic evaluation
(( x = 5 + 3 ))
Increment variable
(( count++ ))
Conditional test
(( x > 10 )) && echo "big"
Capture arithmetic result
result=$(( a * b ))
Complex expression
(( result = (a + b) * c / d ))
说明
(( )) is the shell's arithmetic evaluation construct. It evaluates mathematical expressions and returns success (0) if the result is non-zero, failure (1) if zero. Inside ((...)), variables don't need the $ prefix and whitespace is ignored. Standard C-style operators work as expected. $((...)) performs arithmetic expansion, substituting the result. ((...)) evaluates without substitution (for side effects like assignment). ```bash
FAQ
What is the double-parenthesis command used for?
(( )) is the shell's arithmetic evaluation construct. It evaluates mathematical expressions and returns success (0) if the result is non-zero, failure (1) if zero. Inside ((...)), variables don't need the $ prefix and whitespace is ignored. Standard C-style operators work as expected. $((...)) performs arithmetic expansion, substituting the result. ((...)) evaluates without substitution (for side effects like assignment). ```bash
How do I run a basic double-parenthesis example?
Run `(( x = 5 + 3 ))` in a terminal, then adjust file names, paths, flags, or remote targets for your system.
Where can I find more double-parenthesis examples?
This page includes 5 examples for double-parenthesis, plus related commands for nearby Linux tasks.