2.10. Lua Scripting

Content

1. Introduction

2. DLL required

3. Double Commander functions libraries

3.1. DC libraries

3.1.1. Example with the DC.ExecuteCommand

3.2. System library

3.2.1. Details on SysUtils.FileGetAttr returned value

3.2.2. Example with SysUtils.FileGetAttr

3.2.3. Example using FindFirst, FindNext and FindClose

3.3. Clipboard library

3.3.1. Example of usage clipboard library

3.4. Dialogs library

3.4.1. Buttons displayed in Dialogs.MessageBox

3.4.2. Style of box of Dialogs.MessageBox

3.4.3. Default active button of Dialogs.MessageBox

3.4.4. Returned value of Dialogs.MessageBox

3.4.5. Example of usage of the Dialogs.MessageBox

3.4.6. Example of usage of the Dialogs.InputQuery

3.5. UTF-8 library

3.6. OS library

1. Introduction

Double Commander can execute Lua scripts via cm_ExecuteScript command.

This was introduced with version 0.8 of Double Commander.

It is also possible to write content plugins (.wdx) using Lua script.

More informations on Lua script programming language are available on the web on this link.

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2. DLL required

In order to interpret Lua script file, we need to have a version 5.1 Lua DLL file in the same folder as the executable of Double Commander or in system folder.

By default DC looks for a file with name lua5.1.dll (Windows), liblua5.1.so.0 (Unix or GNU/Linux) or liblua5.1.dylib (Mac OS).

We can use DLL file from LuaJIT project. It may require to manually edit the filename in <PathToLibrary> parameter. LuaJIT combines a high-speed interpreter, written in assembler, with a state-of-the-art JIT compiler. Also we get FFI library, which allows calling external C functions and using C data structures from pure Lua code.

If we're using a 64-bits version of DC, the dll must be the 64-bits version as well.

Generally, the dll will come with DC installation but if for whatever reason it's not there, we may find it under this link or through our packages manager.

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3. Double Commander functions libraries

Double Commander offer a few libraries of functions for our Lua scripts.

Here is the list of them.

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3.1. DC library

This library contains Double Commander specific functions.

It provides all its functions inside the table DC.

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3.1.1. Example with the DC.ExecuteCommand

In this example, we wrote a simple script that will do the following:

1. focus to right panel
2. close all openened tabs
3. switch to a specific folder
4. focus the left panel
5. close all openened tabs
6. switch to a specific folder
7. open a new tab
8. switch to a specific folder

-- 1. Focus on right panel.
DC.ExecuteCommand("cm_FocusSwap", "side=right")

-- 2. Close all tabs.
DC.ExecuteCommand("cm_CloseAllTabs")

-- 3. Switch to a specific directory.
DC.ExecuteCommand("cm_ChangeDir", "e:\\FakeKey\\Documents\\Music")

-- 4. Focus on left panel.
DC.ExecuteCommand("cm_FocusSwap", "side=left")

-- 5. Close all tabs.
DC.ExecuteCommand("cm_CloseAllTabs")

-- 6. Switch to a specific directory.
DC.ExecuteCommand("cm_ChangeDir", "C:\\Users\\Public\\Music")

-- 7. Open a new tab.
DC.ExecuteCommand("cm_NewTab")

-- 8. Switch to a specific directory.
DC.ExecuteCommand("cm_ChangeDir", "e:\\VirtualMachines\\ShareFolder")

Using the internal command cm_ExecuteScript, we may configure a tool bar button that will execute our script.

Assuming this script file is e:\scripts\lua\music.lua, we could have the button configured this way:

Also, we may use the internal Double Commander Editor for editing our scripts.

If filename has .lua file extension, it will be recognized by internal editor and it will provide us syntax highlighting specific for this Lua language:

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3.2. System library

This library contains various system functions.

It provides all its functions inside the table SysUtils.

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3.2.1. Details on SysUtils.FileGetAttr returned value

FileGetAttr returns the attribute settings of file FileName.

The attribute is a OR-ed combination of the following constants:

See an example in the next section.

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3.2.2. Example with SysUtils.FileGetAttr

This following script is an example of usage of the SysUtils.FileGetAttr.

When the parameter is detected to be a directory, it will open a new tab in the active panel and switch to it.

local params = {...}
local myfileattr

if #params == 1 then -- We got at least one parameter?
  myfileattr = SysUtils.FileGetAttr(params[1])
  if myfileattr > 0 then -- We got a valid attribut?
    if math.floor(myfileattr / 0x00000010) % 2 ~= 0 then
      -- bit 4 is set? So it's a directory.
      DC.ExecuteCommand("cm_NewTab")
      DC.ExecuteCommand("cm_ChangeDir", params[1])
    end
  end
end

In the above example, the param[1] is the 1st parameter passed to the script.

When using the internal command cm_ExecuteScript, it will will be the first parameter passed after the script filename.

So in our example, we may program a sample toolbar button like the following:

In this example, the parameter %"0%p will be passed to the script. This will represent, unquoted, the filename of the item currently selected in the active panel at the moment we press the toolbar button.

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3.2.3. Example using FindFirst, FindNext and FindClose

In the following script example, we'll scan the content of the directory we received in parameter and store resulting data into a text file with the filename passed as a second parameter.

This will give us a good idea of the usage of FindFirst, FindNext and FindClose.

local params = {...}

if #params == 2 then -- We got our 2 parameters?
  local Result = nil
  local OutputFile = nil

  OutputFile = io.output(params[2])

  local Handle,FindData = SysUtils.FindFirst(params[1] .. "\\*")
  if Handle ~= nil then
    repeat
      io.write(FindData.Name .. "\r")
      io.write(FindData.Size .. "\r")
      io.write("---------------\r")

      Result,FindData = SysUtils.FindNext(Handle)
    until Result == nil

    SysUtils.FindClose(Handle)
    io.close(OutputFile)
  end
end

In the above example, we need to pass two parameters to our script:

1. param[1] - which is the directory we want the content
2. param[2] - which is the outputfilename to store the result

So it's easy to configure a toolbar button using the internal command cm_ExecuteScript and pass the parameter to accomplish all this.

In this example, the parameter %"0%Ds will be passed to the script as the first parameter. This will represent, unquoted, the directory displayed by the active panel.

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3.3. Clipboard library

Double Commander may provide external clipboard functionality to our Lua scripts.

Following table gives us the related functions:

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3.3.1. Example of usage clipboard library

The following example is using three functions related with the clipboard: Clear, GetAsText and SetAsText.

It's a relative long script but it's good to put together a few functions we've seen above.

It assumes our active panel is currently into a directory with many source text files.

It also assumes we currently have in clipboard a single word and that it will receive as a single parameter the current active folder.

The script will scan the file in that current level of directory and will read the content of them one by one to detect text line that containts the word that was in clipboard.

Then, the filenames of the files that containt at least one line with that word will be place into the clipboard.

Then, the script will use the internal command cm_LoadSelectionFromClip and the files that have the words will then be selected.

Also, at the end, we put back in our clipboard the original word that needed to be searched.

local params = {...}
local Result = nil
local myfileattr
local bFound = false
local sCompleteFilename = ""
local InputFile = nil
local line = ""
local iPosS
local iPosE
local sFileToSelect = ""
local sSearchString = ""

if #params == 1 then -- We got our parameter?
  sSearchString = Clipbrd.GetAsText() -- Get the expression to search.
  Clipbrd.Clear() -- Making sure we have nothing in clipboard.
  DC.ExecuteCommand("cm_MarkUnmarkAll") -- Make sure nothing is selected.

  -- Let's scan one by one all the files of our directory.
  local Handle,FindData = SysUtils.FindFirst(params[1] .. "\\*")
  if Handle ~= nil then
    repeat
      sCompleteFilename = params[1] .. "\\" .. FindData.Name
      myfileattr = SysUtils.FileGetAttr(sCompleteFilename)
      if myfileattr > 0 then -- We got a valid attribut?
        -- We need file, not directory!
        if math.floor(myfileattr / 0x00000010) % 2 == 0 then

          -- Let's now read the file line by line until the the end OR a found.
          InputFile = io.open(sCompleteFilename, "r")
          bFound = false

          while bFound == false do
            line = InputFile:read()
            if line == nil then break end
            iPosS, iPosE = string.find(line, sSearchString)
            if iPosS ~= nil then bFound = true end
          end

          if bFound == true then
            sFileToSelect = sFileToSelect .. FindData.Name .. "\n"
          end

          io.close(InputFile)
        end
      end
      Result,FindData = SysUtils.FindNext(Handle)
    until Result == nil

    SysUtils.FindClose(Handle)
  end

  -- If we've found something, select it!
  if sFileToSelect ~= "" then
    Clipbrd.SetAsText(sFileToSelect)
    DC.ExecuteCommand("cm_LoadSelectionFromClip")
  end

  Clipbrd.SetAsText(sSearchString) -- Restoring what we had in clipboard.
end

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3.4. Dialogs library

This library allows our scripts to interact with user to display message, prompt for answers, etc.

Following table gives us the related functions:

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3.4.1. Buttons displayed in Dialogs.MessageBox

The buttons displayed in the box displayed by Dialogs.MessageBox function are controlled by a OR'ed value with one of the following:

Constant of ButFlags regarding the buttons displayed of Dialogs.MessageBox
Constant value	Buttons displayed, from left to right
0x0000 MB_OK
0x0001 MB_OKCANCEL
0x0002 MB_ABORTRETRYIGNORE
0x0003 MB_YESNOCANCEL
0x0004 MB_YESNO
0x0005 MB_RETRYCANCEL

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3.4.2. Style of box of Dialogs.MessageBox

The style of the box displayed by Dialogs.MessageBox function are controlled by a OR'ed value with one of the following:

Constant of ButFlags regarding the icon and style of Dialogs.MessageBox
Constant value	Style of window
0x0040 MB_ICONINFORMATION	Informative window
0x0030 MB_ICONWARNING	Warning window
0x0020 MB_ICONQUESTION	Confirmation window
0x0010 MB_ICONERROR	Error window

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3.4.3. Default active button of Dialogs.MessageBox

The default active button of the box displayed by Dialogs.MessageBox function are controlled by a OR'ed value with one of the following:

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3.4.4. Returned value of Dialogs.MessageBox

The number returned by the Dialogs.MessageBox function represent the button user has pressed according to the following:

ButPressed value returned based on button pressed of Dialogs.MessageBox
Constant value	Button pressed
0x0000 mrNone	No button pressed
0x0001 mrOK
0x0002 mrCancel
0x0003 mrAbort
0x0004 mrRetry
0x0005 mrIgnore
0x0006 mrYes
0x0007 mrNo

Note: If we press the "x" in top right or press Esc to close the window, then the value of the button "Cancel" is will returned.

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3.4.5. Example of usage of the Dialogs.MessageBox

Here is a little script using Dialogs.MessageBox and the resulting window that will be displayed:

-- Buttons displayed
MB_OK = 0x0000
MB_OKCANCEL = 0x0001
MB_ABORTRETRYIGNORE = 0x0002
MB_YESNOCANCEL = 0x0003
MB_YESNO = 0x0004
MB_RETRYCANCEL = 0x0005

-- Box style
MB_ICONINFORMATION = 0x0040
MB_ICONWARNING = 0x0030
MB_ICONQUESTION = 0x0020
MB_ICONERROR = 0x0010

-- Default button
MB_DEFBUTTON1 = 0x0000
MB_DEFBUTTON2 = 0x0100
MB_DEFBUTTON3 = 0x0200

-- Returned button pressed
mrNone = 0x0000
mrOK = 0x0001
mrCancel = 0x0002
mrAbort = 0x0003
mrRetry = 0x0004
mrIgnore = 0x0005
mrYes = 0x0006
mrNo = 0x0007

ButFlags = MB_YESNO + MB_ICONQUESTION + MB_DEFBUTTON2
ButPressed = Dialogs.MessageBox("Do you want to quit?", "Question", ButFlags)

if ButPressed == mrYes then
  DC.ExecuteCommand("cm_Exit")
end

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3.4.6. Example of usage of the Dialogs.InputQuery

Here is a little script using Dialogs.InputQuery and the resulting window that will be displayed:

bAck, sAnswer = Dialogs.InputQuery("Identification", "Enter your name:", false, "John")

if bAck == true then
  Dialogs.MessageBox("Hello " .. sAnswer .. "!", "Welcome!", 0x0040)
end

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3.5. UTF-8 library ^[*]

This library provides basic support for UTF-8 encoding.

It provides all its functions inside the table LazUtf8.

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3.6. OS library

This library contains functions related with the operating system where Double Commander is running.

Here is the list of available functions in this library:

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