Re: Reading a conf file

[steve donovan <steve.j.donovan@...>]

On Thu, Sep 29, 2016 at 7:19 AM, Russell Haley <russ.haley@gmail.com> wrote:
> About the saving of values: yes, it is important not to molest the
> original file. I would like to be able to work with conf files in
> FreeBSD lik rc.conf and leave them intact.

Ah, that suggests a simple solution:

(1) read all the lines into an array
local f, e = io.open(file)
-- check that e!
local lines = {}
for line in f:lines() do
  table.insert(lines,line)
end
f:close()

(2) process only non-blank or lines not starting with #
local values = {}
local value_lines = {}
for i,line in ipairs(lines) do
  if not (line:match '^%s*$' or line:match '^#') then
    local var,val = line:match('^([^=]+)=(.+)')
    values[var] = val
    value_lines[var] = i
  end
end

The values table is what you need.  Updating a var is like so

(3)
lines[value_lines[var]] = var..'='..new_value

and then write out
local f,e = io.open(file,'w');
for i,line in ipairs(lines) do
   f:write(line,'\n')
end
f:close()