refactor parallel code

openos/unalias.lua

@@ -0,0 +1,19 @@
+local shell = require("shell")
+
+local args = shell.parse(...)
+if #args < 1 then
+  io.write("Usage: unalias <name>...\n")
+  return 2
+end
+local e = 0
+
+for _,arg in ipairs(args) do
+  local result = shell.getAlias(arg)
+  if not result then
+    io.stderr:write(string.format("unalias: %s: not found\n", arg))
+    e = 1
+  else
+    shell.setAlias(arg, nil)
+  end
+end
+return e