Shell：将变量插入命令[duplicate]

This question already has an answer here:

这个问题在这里已有答案:

• Difference between single and double quotes in Bash 5 answers

Bash 5答案中单引号和双引号之间的区别

I'm trying to find a way the use a variable in this command to replace -10 with n_days var:

我试图找到一种方法,在此命令中使用变量用n_days var替换-10:

   n_days= -10
   date_prefix=$(date -d '-10 day' +%Y/%m/%d)

I tried this way but it didn't work:

我试过这种方式,但它不起作用:

   date_prefix=$(date -d '${n_days} day' +%Y/%m/%d)

1 个解决方案

#1

Two things:

1. Declare your variable properly (there is a space in your example)

正确声明您的变量(示例中有一个空格)

2. Use double quotes in place of single quotes to allow the variable to be interpolated

使用双引号代替单引号以允许插值变量

So:

n_days=-10
date_prefix=$(date -d "$n_days day" +%Y/%m/%d)