在shell脚本中声明变量的方法

Question

以下两种在shell脚本中声明变量的方法有什么区别？

var='some/path'

var=${var:-"some/path"}

Answer 1

#this will set var value with some/path, 
#no matter var is empty or not (overwrite)
var='some/path' 


# this will set value of var to "some/path" 
#only if var is empty/or not declared yet.
var=${var:-"some/path"} 

Answer 2

var='some/path'

总是将var设置为some / path

var=${var:-"some/path"}

如果尚未设置var，则仅将var设置为某个/ path。如果已设置，则其值不会更改。