Re: Reading a conf file

[Russell Haley <russ.haley@...>]

Hi Valentin,

I was unable to make this work at all. I kept getting "attempt to call
a nil value (global 'loadstring')" which PIL online tells me is normal
for a syntax error. I used assert but didn't get any extra
information.

conf file contents:

server_port=8000
server_url = localost
base_path = confFilePath
data_dir_name = data

In your parsing, you had left a trailing ',' that I thought was the
problem, I removed it with string.sub, but that did not fix the issue.
Here is the code:

local function loadConfFile (fn)
    local f = io.open(fn, 'r')
    if f==nil then return {} end
    local str = f:read('*a')..'\n'
    f:close()
    local res = 'return {'
    for line in str:gmatch("(.-)[\r\n]") do
        line = line:gsub('^%s*(.-)%s*$"', '%1') -- trim line
        -- ignore empty lines and comments
        if line~='' and line:sub(1,1)~='#' then
            line = line:gsub("'", "\\'") -- escape all '
            line = line:gsub("=%s*", "='", 1)
            res = res..line.."',"
        end
    end
    res = res:sub(1, -2)
    res = res..'}'

    print(res)
  -- return loadstring(res)
    --return {server_port='8000',server_url ='localost',base_path
='confFilePath',data_dir_name ='data'}
    --local t = assert(loadstring(res)())
    return loadstring([[{"server_port"="8000","server_url"="localhost"}]])()
end

Note the various debugging attempts at the end. The output is a valid
table because I can manually return the table value from print(res).

hmmm...?

Russ

On Wed, Sep 28, 2016 at 3:55 PM, Valentin <vsl@dasdeck.com> wrote:
> Sean Conner wrote:
> [ snip ]
>
>>   You already have a parser available to you---Lua.  If the config file is
>> just what you said:
>>
>>       a=series
>>       of=key
>>       value=pairs
>>
>> A small change:
>>
>>       a='series'
>>       of='key'
>>       value='pairs'
>>       and_a_number=3
>>
>> and that can be read in as:
>>
>>       CONF = {} -- your data will end up here
>>       f = loadfile("my-configfile.txt","t",CONF)
>>       f()
>>
>>       print(CONF.a,CONF.and_a_number)
>
> Based on the same idea, but without requiring to add quotes to the conf
> file, here a simple function for reading such "INI-like" conf files into
> a table. All table values will be strings, and have to be casted
> manually to other types if needed.
>
> function loadConfFile (fn)
>   local f = io.open(fn, 'r')
>   if f==nil then return {} end
>   local str = f:read('*a')..'\n'
>   f:close()
>   local res = 'return {'
>   for line in str:gmatch("(.-)[\r\n]") do
>     line = line:gsub('^%s*(.-)%s*$"', '%1') -- trim line
>     -- ignore empty lines and comments
>     if line~='' and line:sub(1,1)~='#' then
>       line = line:gsub("'", "\\'") -- escape all '
>       line = line:gsub("=%s*", "='", 1)
>       res = res..line.."',"
>     end
>   end
>   res = res..'}'
>   return loadstring(res)()
> end
>
>
> Usage:
> ======
>
> -- contents of test.conf
> a   =  23
>
> b=hello 'world'
>
> # just a comment
> c =    hello world
>
> -- /contents of test.conf
>
> local config = loadConfFile('test.conf')
> for k,v in pairs(conf) do
>   print(k, v)
> end
>
> --> a       23
> --> c       hello world
> --> b       hello 'world'
>
> Valentin
>