bash 如何检查变量是否具有偶数值？
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How do I check whether a variable has an even numeric value?
提问by lizarisk
How should I change this to check whether valhas an even or odd numeric value?
我应该如何更改它以检查是否val具有偶数或奇数数值？
val=2
if $((RANDOM % $val)); ...
回答by Fredrik Pihl
$ a=4
$ [ $((a%2)) -eq 0 ] && echo "even"
even
$ a=3
$ [ $((a%2)) -eq 0 ] && echo "even"
回答by Paul
foo=6
if [ $((foo%2)) -eq 0 ];
then
echo "even";
else
echo "odd";
fi
回答by chepner
$(( ... ))is just an expression. Its result appears where bashexpects a command.
$(( ... ))只是一种表达。它的结果出现在bash需要命令的地方。
A POSIX-compatible solution would be:
POSIX 兼容的解决方案是：
if [ "$(( RANDOM % 2))" -ne 0 ];
but since RANDOMisn't defined in POSIX either, you may as well use the right bashcommand for the job: an arithmetic evaluation compound command:
但由于RANDOM也没有在 POSIX 中定义，您也可以使用正确的bash命令来完成这项工作：算术评估复合命令：
if (( RANDOM % 2 )); then
