Help with writing to a file.

[AKA_Clutter]

Hi all,

I am trying to write information to a file and I am having an issue. 

 

I have commented out the sanitize lines in MissionScripting.lua and I am able to write to a file.  However, I want to add a check to make sure that DCS sanitation has been disabled.  I do this with an if statement, but this ends up generating an error.  Here is the sbnipet of code that I am having issues with.

local function Write_Mission_Stats ()

  trigger.action.outTextForCoalition(2,MSG_Header .. "TEST - Simple test to write to file    TEST" .. MSG_Footer, 15)
--  Test_File_Handle = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w") 
  if io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w") ~= nil then
    local Generate_Mission_Config_Report_Tbl_Outstring = Mission_Config_Report_Tbl ()
    Test_File_Handle = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w")
    Test_File_Handle:write("===========================\n")
    Test_File_Handle:write("Mission Stats for AKA Campaign\n")
    Test_File_Handle:write("===============================\n")
    Test_File_Handle:write(Generate_Mission_Config_Report_Tbl_Outstring)
  else
    trigger.action.outTextForCoalition(2, "\n*************************************\n\nNot able to open wirte file. \n\n**********************", 15)
  end
end

-- Next line is to call the function to write mission states to a file.
  timer.scheduleFunction(Write_Mission_Stats, {}, timer.getTime() + 15*Sec_per_min)         

The error message is that the line with "    Test_File_Handle:write("===========================\n")" attempt to index global Test_Handle(a nil) value).  I check after the error and a file named "AKA_Test_File.txt" has been created,but is empty.  

If I remove the if statement, the code works fine and a file is written.

I tried adding "Test_File_Handle = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w")" as the text condition to the if statement, but it didn't like that at all.

Can any tell me why this is happening, or a better way to check and see if I can write a file and not generate an error that stops the script.

Thanks,

[Kanelbolle]

16 hours ago, AKA_Clutter said:

Hi all,

I am trying to write information to a file and I am having an issue. 

 

I have commented out the sanitize lines in MissionScripting.lua and I am able to write to a file.  However, I want to add a check to make sure that DCS sanitation has been disabled.  I do this with an if statement, but this ends up generating an error.  Here is the sbnipet of code that I am having issues with.

local function Write_Mission_Stats ()

  trigger.action.outTextForCoalition(2,MSG_Header .. "TEST - Simple test to write to file    TEST" .. MSG_Footer, 15)
--  Test_File_Handle = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w") 
  if io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w") ~= nil then
    local Generate_Mission_Config_Report_Tbl_Outstring = Mission_Config_Report_Tbl ()
    Test_File_Handle = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w")
    Test_File_Handle:write("===========================\n")
    Test_File_Handle:write("Mission Stats for AKA Campaign\n")
    Test_File_Handle:write("===============================\n")
    Test_File_Handle:write(Generate_Mission_Config_Report_Tbl_Outstring)
  else
    trigger.action.outTextForCoalition(2, "\n*************************************\n\nNot able to open wirte file. \n\n**********************", 15)
  end
end

-- Next line is to call the function to write mission states to a file.
  timer.scheduleFunction(Write_Mission_Stats, {}, timer.getTime() + 15*Sec_per_min)         

The error message is that the line with "    Test_File_Handle:write("===========================\n")" attempt to index global Test_Handle(a nil) value).  I check after the error and a file named "AKA_Test_File.txt" has been created,but is empty.  

If I remove the if statement, the code works fine and a file is written.

I tried adding "Test_File_Handle = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w")" as the text condition to the if statement, but it didn't like that at all.

Can any tell me why this is happening, or a better way to check and see if I can write a file and not generate an error that stops the script.

Thanks,

Look here how to write to files:

 

Not sure if this works at all. : if io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt","w") ~= nil then

Should maybe be:
if Test_File_Handle == nil then

The file is not open at this point, so why are you checking if it is open and opening it again in the code below ?

 

and you should have this at the end of the write.

 

Test_File_Handle:close()
Test_File_Handle = nil

 

You can also see here for a lua example for checking if the file is open or not:

https://stackoverflow.com/questions/28867248/lua-check-if-a-file-is-open

 

 

Edited June 20, 2023 by Kanelbolle

[AKA_Clutter]

Thanks for the response Kanelbolle.

The reason I am checking to see if I get an error when trying to open the file is to try and avoid a runtime error that stops the script.

I also posted this question on the Stack Overflow board.  The response I got there, was that I was opening the file TWICE is rapid succession., which may caused a Time of check to Time of Use error (Time-of-check_to_time-of-use).  As being new to programming and lua, I would never have figured this out.

The responder also suggested a better way to do what I wanted to do.

The key seems to be to open the file and assign that to a handle (Variable) and also capture the error, if the file can't be opened.  I think the key is the follwoing line.

              local Test_File_Handle, err = io.open(FILENAME, "w")

Anyway, my revised code is shown below and seems to work.  I haven't tested to see what happens if I can't write the file to start with.

 

  local function Write_Mission_Stats ()

    trigger.action.outTextForCoalition(2,MSG_Header .. "TEST - Simple test to write to file    TEST" .. MSG_Footer, 15)

---[[  ALternate Method
  local Test_File_Handle, err = io.open("C:\\Users\\Nathan\\Saved Games\\DCS.openbeta\\AKA_Test_File.txt", "w")  -- For Clutter's Comuter
--  local Generate_A2A_Summary_Stats_OutString = Summary_Stats_Report_Tbl (Index_TBL)
    if not Test_File_Handle then
        -- failed to open file, let's display the error
--        print(err) -- or error(err), or whatever debugging function
        trigger.action.outTextForCoalition(2,MSG_Header .. "FIle was not opened\n" .. MSG_Footer, 15)
        trigger.action.outTextForCoalition(2,MSG_Header .. err .. MSG_Footer, 15)
    else
        local Generate_Mission_Config_Report_Tbl_Outstring = Mission_Config_Report_Tbl ()

        trigger.action.outTextForCoalition(2,MSG_Header .. "TEST PRINT BEFORE WRITE CALL" ..  MSG_Footer, 15)     -- Output summary talbe of A2A groups
        trigger.action.outTextForCoalition(2,MSG_Header .. Generate_A2A_Summary_Stats_OutString ..  MSG_Footer, 15)     -- Output summary talbe of A2A groups
        -- opened the file, write some data
        Test_File_Handle:write("===============================\n")
        Test_File_Handle:write("   Mission Stats for AKA Campaign\n")
        
-- Close the file        
        Test_File_Handle:close()
    end
  return
  end

-- Next line is to call the function to write mission states to a file.
  timer.scheduleFunction(Write_Mission_Stats, {}, timer.getTime() + 15*Sec_per_min)