3 files changed, 19 insertions, 9 deletions

diff --git a/src/luarocks/fs/lua.lua b/src/luarocks/fs/lua.lua
index 14bf0369..145a60de 100644
--- a/src/luarocks/fs/lua.lua
+++ b/src/luarocks/fs/lua.lua
@@ -1045,7 +1045,7 @@ function fs_lua.current_user()
 end
 
 function fs_lua.is_superuser()
-   return false
+   return posix.geteuid() == 0
 end
 
 -- This call is not available on all systems, see #677
diff --git a/src/luarocks/fs/unix.lua b/src/luarocks/fs/unix.lua
index 28189089..61569e30 100644
--- a/src/luarocks/fs/unix.lua
+++ b/src/luarocks/fs/unix.lua
@@ -176,14 +176,6 @@ function unix.tmpname()
    return os.tmpname()
 end
 
-function unix.current_user()
-   return os.getenv("USER")
-end
-
-function unix.is_superuser()
-   return os.getenv("USER") == "root"
-end
-
 function unix.export_cmd(var, val)
    return ("export %s='%s'"):format(var, val)
 end
diff --git a/src/luarocks/fs/unix/tools.lua b/src/luarocks/fs/unix/tools.lua
index f0c0a05c..b7fd4de5 100644
--- a/src/luarocks/fs/unix/tools.lua
+++ b/src/luarocks/fs/unix/tools.lua
@@ -297,4 +297,22 @@ function tools.is_file(file)
    return fs.execute(vars.TEST, "-f", file)
 end
 
+function tools.current_user()
+   local user = os.getenv("USER")
+   if user then
+      return user
+   end
+   local pd = io.popen("whoami", "r")
+   if not pd then
+      return ""
+   end
+   user = pd:read("*l")
+   pd:close()
+   return user
+end
+
+function tools.is_superuser()
+   return fs.current_user() == "root"
+end
+
 return tools