“ var = $ {var：-word}”和“ var = $ {var：= word}”之间有什么区别？

“ var = $ {var：-word}”和“ var = $ {var：= word}”之间有什么区别？

使用

var

两次时，您看不到示例的差异，但是可以使用两个不同的变量来查看差异：

foo=${bar:-something}echo $foo # somethingecho $bar # no assignement to bar, bar is still emptyfoo=${bar:=something}echo $foo # somethingecho $bar # something too, as there's an assignement to bar