refactor parallel code

openos/ln.lua

@@ -0,0 +1,35 @@
+local component = require("component")
+local fs = require("filesystem")
+local shell = require("shell")
+
+local args = shell.parse(...)
+if #args == 0 then
+  io.write("Usage: ln <target> [<name>]\n")
+  return 1
+end
+
+local target_name = args[1]
+local target = shell.resolve(target_name)
+
+-- don't link from target if it doesn't exist, unless it is a broken link
+if not fs.exists(target) and not fs.isLink(target) then
+  io.stderr:write("ln: failed to access '" .. target_name .. "': No such file or directory\n")
+  return 1
+end
+
+local linkpath
+if #args > 1 then
+  linkpath = shell.resolve(args[2])
+else
+  linkpath = fs.concat(shell.getWorkingDirectory(), fs.name(target))
+end
+
+if fs.isDirectory(linkpath) then
+  linkpath = fs.concat(linkpath, fs.name(target))
+end
+
+local result, reason = fs.link(target_name, linkpath)
+if not result then
+  io.stderr:write(reason..'\n')
+  return 1
+end