added basic support for symbolic links, pretty untested as of yet, though. they're kind of like mounts in that they have to be re-created after a reboot.

assets/opencomputers/lua/rom/bin/ln.lua

@@ -0,0 +1,22 @@
+local component = require("component")
+local fs = require("filesystem")
+local shell = require("shell")
+
+local dirs = shell.parse(...)
+if #dirs == 0 then
+  print("Usage: ln <target> [<name>]")
+  return
+end
+
+local target = shell.resolve(dirs[1])
+local linkpath
+if #dirs > 1 then
+  linkpath = shell.resolve(dirs[2])
+else
+  linkpath = fs.concat(shell.getWorkingDirectory(), fs.name(target))
+end
+
+local result, reason = fs.link(target, linkpath)
+if not result then
+  print(reason)
+end

assets/opencomputers/lua/rom/bin/ls.lua

@@ -43,7 +43,9 @@ for i = 1, #dirs do
       end
     end
     for _, f in ipairs(lsf) do
-      if f:sub(-4) == ".lua" then
+      if fs.isLink(fs.concat(path, f)) then
+        setColor(0xFFAA00)
+      elseif f:sub(-4) == ".lua" then
         setColor(0x00FF00)
       else
         setColor(0xFFFFFF)

assets/opencomputers/lua/rom/lib/filesystem.lua

@@ -3,7 +3,7 @@ local unicode = require("unicode")
 
 local filesystem, fileStream = {}, {}
 local isAutorunEnabled = true
-local mtab = {children={}}
+local mtab = {children={}, links={}}
 
 local function segments(path)
   path = path:gsub("\\", "/")
@@ -31,19 +31,29 @@ local function segments(path)
   return parts
 end
 
-local function findNode(path, create)
+local function findNode(path, create, depth)
   checkArg(1, path, "string")
+  depth = depth or 0
+  if depth > 100 then
+    error("link cycle detected")
+  end
   local parts = segments(path)
   local node = mtab
-  for i = 1, #parts do
-    if not node.children[parts[i]] then
-      if create then
-        node.children[parts[i]] = {children={}, parent=node}
+  while #parts > 0 do
+    local part = parts[1]
+    if not node.children[part] then
+      if node.links[part] then
+        return findNode(filesystem.concat(node.links[part], table.concat(parts, "/", 2)), create, depth + 1)
       else
-        return node, table.concat(parts, "/", i)
+        if create then
+          node.children[part] = {children={}, links={}, parent=node}
+        else
+          return node, table.concat(parts, "/")
+        end
       end
     end
-    node = node.children[parts[i]]
+    node = node.children[part]
+    table.remove(parts, 1)
   end
   return node
 end
@@ -111,6 +121,24 @@ function filesystem.get(path)
   return nil, "no such file system"
 end
 
+function filesystem.isLink(path)
+  local node, rest = findNode(filesystem.path(path))
+  return not rest and node.links[filesystem.name(path)] ~= nil
+end
+
+function filesystem.link(target, linkpath)
+  checkArg(1, target, "string")
+  checkArg(2, linkpath, "string")
+
+  if filesystem.exists(linkpath) then
+    return nil, "file already exists"
+  end
+
+  local node = findNode(filesystem.path(linkpath), true)
+  node.links[filesystem.name(linkpath)] = target
+  return true
+end
+
 function filesystem.mount(fs, path)
   checkArg(1, fs, "string", "table")
   if type(fs) == "string" then
@@ -119,6 +147,10 @@ function filesystem.mount(fs, path)
   assert(type(fs) == "table", "bad argument #1 (file system proxy or address expected)")
   checkArg(2, path, "string")
 
+  if path ~= "/" and filesystem.exists(path) then
+    return nil, "file already exists"
+  end
+
   local node = findNode(path, true)
   if node.fs then
     return nil, "another filesystem is already mounted here"
@@ -217,7 +249,7 @@ end
 
 function filesystem.exists(path)
   local node, rest = findNode(path)
-  if not rest then -- virtual directory
+  if not rest or node.links[rest] then -- virtual directory or symbolic link
     return true
   end
   if node.fs then
@@ -266,9 +298,12 @@ function filesystem.list(path)
     result = {}
   end
   if not rest then
-    for k, _ in pairs(node.children) do
+    for k in pairs(node.children) do
       table.insert(result, k .. "/")
     end
+    for k in pairs(node.links) do
+      table.insert(result, k)
+    end
   end
   table.sort(result)
   local i = 0
@@ -279,6 +314,9 @@ function filesystem.list(path)
 end
 
 function filesystem.makeDirectory(path)
+  if filesystem.exists(path) then
+    return nil, "file or directory with that name already exists"
+  end
   local node, rest = findNode(path)
   if node.fs and rest then
     return node.fs.makeDirectory(rest)
@@ -290,29 +328,49 @@ function filesystem.makeDirectory(path)
 end
 
 function filesystem.remove(path)
-  local node, rest = findNode(path)
-  if node.fs and rest then
-    return node.fs.remove(rest)
+  local node, rest = findNode(filesystem.path(path))
+  local name = filesystem.name(path)
+  if node.children[name] then
+    node.children[name] = nil
+    return true
+  elseif node.links[name] then
+    node.links[name] = nil
+    return true
+  else
+    node, rest = findNode(path)
+    if node.fs and rest then
+      return node.fs.remove(rest)
+    end
+    return nil, "no such file or directory"
   end
-  return nil, "no such non-virtual directory"
 end
 
 function filesystem.rename(oldPath, newPath)
-  local oldNode, oldRest = findNode(oldPath)
-  local newNode, newRest = findNode(newPath)
-  if oldNode.fs and oldRest and newNode.fs and newRest then
-    if oldNode.fs.address == newNode.fs.address then
-      return oldNode.fs.rename(oldRest, newRest)
-    else
-      local result, reason = filesystem.copy(oldPath, newPath)
-      if result then
-        return filesystem.remove(oldPath)
+  if filesystem.isLink(oldPath) then
+    local node, rest = findNode(filesystem.path(oldPath))
+    local target = node.links[filesystem.name(oldPath)]
+    local result, reason = filesystem.link(target, newPath)
+    if result then
+      filesystem.remove(oldPath)
+    end
+    return result, reason
+  else
+    local oldNode, oldRest = findNode(oldPath)
+    local newNode, newRest = findNode(newPath)
+    if oldNode.fs and oldRest and newNode.fs and newRest then
+      if oldNode.fs.address == newNode.fs.address then
+        return oldNode.fs.rename(oldRest, newRest)
       else
-        return nil, reason
+        local result, reason = filesystem.copy(oldPath, newPath)
+        if result then
+          return filesystem.remove(oldPath)
+        else
+          return nil, reason
+        end
       end
     end
+    return nil, "trying to read from or write to virtual directory"
   end
-  return nil, "trying to read from or write to virtual directory"
 end
 
 function filesystem.copy(fromPath, toPath)