Expand tilde to home directory

Question

I have a program that accepts a destination folder where files will be created. My program should be able to handle absolute paths as well as relative paths. My problem is that I don't know how to expand ~ to the home directory.

My function to expand the destination looks like this. If the path given is absolute it does nothing otherwise it joins the relative path with the current working directory.

import "path" import "os"  // var destination *String is the user input  func expandPath() {         if path.IsAbs(*destination) {                 return         }         cwd, err := os.Getwd()         checkError(err)         *destination = path.Join(cwd, *destination) } 

Since path.Join doesn't expand ~ it doesn't work if the user passes something like ~/Downloads as the destination.

How should I solve this in a cross platform way?

Answer 1

Go provides the package os/user, which allows you to get the current user, and for any user, their home directory:

usr, _ := user.Current() dir := usr.HomeDir 

Then, use path/filepath to combine both strings to a valid path:

if path == "~" {     // In case of "~", which won't be caught by the "else if"     path = dir } else if strings.HasPrefix(path, "~/") {     // Use strings.HasPrefix so we don't match paths like     // "/something/~/something/"     path = filepath.Join(dir, path[2:]) } 

(Note that user.Current() is not implemented in the go playground (likely for security reasons), so I can't give an easily runnable example).

Answer 2

In general the ~ is expanded by your shell before it gets to your program. But there are some limitations.

In general is ill-advised to do it manually in Go.

I had the same problem in a program of mine and what I have understood is that if I use the flag format as --flag=~/myfile, it is not expanded. But if you run --flag ~/myfile it is expanded by the shell (the = is missing and the filename appears as a separate "word").