bash - 如何使 bash realpath 与变量一起工作？

Question

我跑

#!/bin/bash

id="~/.ssh/foo"

realpath ~/.ssh/foo
realpath "~/.ssh/foo"
realpath $id
realpath "$id"

期望 4 行相同的输出，没有错误。我得到的是

/home/me/.ssh/foo
realpath: '~/.ssh/foo': No such file or directory
realpath: '~/.ssh/foo': No such file or directory
realpath: '~/.ssh/foo': No such file or directory

为什么只有第一个成功？

我想要做

echo "Enter a path: "
read p
p="$(realpath "$p")"
echo "The real path is $p"

由于此错误，这不起作用。我需要做什么？