bash Shell脚本：如何检查变量是否为空
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/48261038/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Shell Script : How to check if variable is null or no
提问by TheRight
I want to check if variable is null or no.
我想检查变量是否为空。
My code is :
我的代码是：
list_Data="2018-01-15 10:00:00.000|zQfrkkiabiPZ||04|
2018-01-15 10:00:00.000|zQgKLANvbRWg||04|
2018-01-15 10:00:00.000|zQgTEbJjWGjf||01|
2018-01-15 10:00:00.000|zQgwF1YJLnAT||01|"
echo "list_Data"
if [[ -z "list_Data" ]]
then
echo "not Empty"
else
echo "empty"
fi
The Output is :
输出是：
2018-01-15 10:00:00.000|zQfrkkiabiPZ||04|
2018-01-15 10:00:00.000|zQgKLANvbRWg||04|
2018-01-15 10:00:00.000|zQgTEbJjWGjf||01|
2018-01-15 10:00:00.000|zQgwF1YJLnAT||01|
empty
The problem that the varible contain values but i have always empty message please help.
变量包含值但我总是有空消息的问题请帮助。
回答by RavinderSingh13
Try following, you should change from -zto -nas follows and add $to your variable too.
尝试以下，您应该从-z改为-n如下并添加$到您的变量中。
if [[ -n "$list_Data" ]]
then
echo "not Empty"
else
echo "empty"
fi
Explanation:From man testpage as follows(It checks if a variable is having any value or not. If it has any value then condition is TRUE, if not then it is FALSE.)
说明：从man test页面如下（它检查一个变量是否有任何值。如果有任何值，则条件为真，如果没有，则为假。）
-n STRING the length of STRING is nonzero
-n STRING the length of STRING is nonzero
回答by Alfe
if [[ -z "$list_Data" ]]
then
echo "Empty"
else
echo "Not empty"
fi
Try it like this. (Added $and switched cases.)
像这样试试。（添加$和切换案例。）
