Added system library to handle running external commands on different operating systems in a transparent manner. Added file and path quoting that is cross platform compatible. Changed gimp.lua to use the new utilities.

contrib/gimp.lua

@@ -65,6 +65,7 @@
 
 local dt = require "darktable"
 local df = require "lib/dtutils.file"
+local dtsys = require "lib/dtutils.system"
 require "official/yield"
 local gettext = dt.gettext
 local gimp_widget = nil
@@ -94,7 +95,7 @@ local function group_if_not_member(img, new_img)
     dt.print_log("Added to group")
   end
 end
-
+--[[
 local function sanitize_filename(filepath)
   local path = df.get_path(filepath)
   local basename = df.get_basename(filepath)
@@ -104,7 +105,7 @@ local function sanitize_filename(filepath)
 
   return path .. sanitized .. "." .. filetype
 end
-
+]]
 local function show_status(storage, image, format, filename,
   number, total, high_quality, extra_data)
     dt.print(string.format(_("Export Image %i/%i"), number, total))
@@ -130,7 +131,7 @@ local function gimp_edit(storage, image_table, extra_data) --finalize
   img_list = ""
 
   for _,exp_img in pairs(image_table) do
-    exp_img = sanitize_filename(exp_img)
+    exp_img = df.sanitize_filename(exp_img)
     img_list = img_list ..exp_img.. " "
   end
 
@@ -141,7 +142,7 @@ local function gimp_edit(storage, image_table, extra_data) --finalize
 
   dt.print_log(gimpStartCommand)
 
-  dt.control.execute( gimpStartCommand)
+  dtsys.external_command(gimpStartCommand)
 
   -- for each of the image, exported image pairs
   --   move the exported image into the directory with the original

lib/dtutils/file.lua

@@ -1,5 +1,6 @@
 local dtutils_file = {}
 local dt = require "darktable"
+local ds = require "lib/dtutils.string"
 
 local log = require "lib/dtutils.log"
 
@@ -529,4 +530,28 @@ function dtutils_file.executable_path_widget(executables)
   return box
 end
 
+dtutils_file.libdoc.functions["sanitize_filename"] = {
+  Name = [[sanitize_filename]],
+  Synopsis = [[make a filename safe to pass as an argument]],
+  Usage = [[local df = require "lib/dtutils.file"
+
+    local sanitized_filename = df.sanitize_filename(filename)
+      filename - string - a filepath and filename]],
+  Description = [[sanitize_file places quotes around the filename in an
+    operating system specific manner.  The result is safe to pass as 
+    an argument to the operating system.]],
+  Return_Value = [[sanitized_filename - string - quoted filename]],
+  Limitations = [[]],
+  Example = [[]],
+  See_Also = [[]],
+  Reference = [[]],
+  License = [[]],
+  Copyright = [[]],
+}
+
+function dtutils_file.sanitize_filename(filename)
+  return ds.sanitize(filename)
+end
+
 return dtutils_file
+

lib/dtutils/string.lua

@@ -1,4 +1,7 @@
 local dtutils_string = {}
+
+local dt = require "darktable"
+
 dtutils_string.libdoc = {
   Name = [[dtutils.string]],
   Synopsis = [[a library of string utilities for use in darktable lua scripts]],
@@ -170,4 +173,35 @@ function dtutils_string.urlencode(str)
   return str
 end
 
+
+dtutils_string.libdoc.functions["sanitize"] = {
+  Name = [[sanitize]],
+  Synopsis = [[surround a string in quotes making it safe to pass as an argument]],
+  Usage = [[local ds = require "lib/dtutils.string"
+
+    local result = ds.sanitize(str)
+      str - string - the string that needs to be made safe]],
+  Description = [[sanitize converts a string into a version suitable for
+    use passing as an argument in a system command.]],
+  Return_Value = [[result - string - a websafe string]],
+  Limitations = [[]],
+  Example = [[]],
+  See_Also = [[]],
+  Reference = [[]],
+  License = [[]],
+  Copyright = [[]],
+}
+
+function dtutils_string.sanitize(str)
+  local result = ""
+
+  if dt.configuration.running_os == "windows" then
+    result = '"' .. str .. '"'
+  else
+    result = "'" .. str .. "'"
+  end
+  
+  return result
+end
+
 return dtutils_string

lib/dtutils/system.lua

@@ -0,0 +1,103 @@
+local dtutils_system = {}
+
+local dt = require "darktable"
+
+dtutils_system.libdoc = {
+  Name = [[dtutils.system]],
+  Synopsis = [[a library of system utilities for use in darktable lua scripts]],
+  Usage = [[local ds = require "lib/dtutils.system"]],
+  Description = [[This library contains routines for interfacing to the operating system from
+    darktable lua scripts.]],
+  Return_Value = [[du - library - the darktable lua system library]],
+  Limitations = [[]],
+  Example = [[]],
+  See_Also = [[]],
+  Reference = [[]],
+  License = [[This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.]],
+  Copyright = [[Copyright (c) 2018 Bill Ferguson <wpferguson@gmail.com>]],
+  functions = {}
+}
+
+dtutils_system.libdoc.functions["external_command"] = {
+  Name = [[external_command]],
+  Synopsis = [[pass a command to the operating system for execution and return the result]],
+  Usage = [[local dsys = require "lib/dtutils.system"
+
+    local result = dsys.external_command(command)
+      command - string - a string containing the command and arguments to be passed to the operating system for execution.]],
+  Description = [[external_command passes a command to the operating system for execution and returns the results.]], 
+  Return_Value = [[result - the return value signalling success or failure.]],
+  Limitations = [[]],
+  Example = [[]],
+  See_Also = [[]],
+  Reference = [[]],
+  License = [[]],
+  Copyright = [[]],
+}
+
+function dtutils_system.external_command(command)
+  local result = nil
+
+  if dt.configuration.running_os == "windows" then
+    result = dtutils_system.windows_command(command)
+  else
+    result = dt.control.execute(command)
+  end
+
+  return result
+end
+
+dtutils_system.libdoc.functions["windows_command"] = {
+  Name = [[windows_command]],
+  Synopsis = [[pass a command to the windows operating system for execution and return the result]],
+  Usage = [[local dsys = require "lib/dtutils.system"
+
+    local result = dsys.windows_command(command)
+      command - string - a string containing the command and arguments to be passed to the operating system for execution.]],
+  Description = [[The normal method of executing an operating system command is using dt.control.execute(), but that doesn't 
+    work with Windows when more than one item in the command is quoted.  In order to ensure command execution on Windows we 
+    create a batch file in the temporary directory, put the command in it, execute the batch file, then return the result.]], 
+  Return_Value = [[result - the return value signalling success or failure.]],
+  Limitations = [[]],
+  Example = [[]],
+  See_Also = [[]],
+  Reference = [[]],
+  License = [[]],
+  Copyright = [[]],
+}
+
+function dtutils_system.windows_command(command)
+  local result = 1
+
+  local fname = dt.configuration.tmp_dir .. "/run_command.bat"
+
+  local file = io.open(fname, "w")
+  if file then
+    dt.print_log("opened file")
+    command = string.gsub(command, "%%", "%%%%") -- escape % from windows shell
+    file:write(command)
+    file:close()
+
+    result = dt.control.execute(fname)
+    dt.print_log("result from windows command was " .. result)
+
+    os.remove(fname)
+  else
+    dt.print_error("Windows command failed: unable to create batch file")
+  end
+
+  return result
+end
+
+return dtutils_system