3 replies to this topic

[lieudusty]

Hi everyone! =D

I'm wondering how I can use io or fs to delete a line in a file. I know how to make lines and things but I don't see how to delete a line. Can someone help?

[Kingdaro]

I'd go about this by reading the entire file, taking each line and putting it in a table, then removing whichever line you want from the table, and rewriting all of the lines in a table.

--get file content
local file = fs.open('filepath','r')
local filedata = file.readAll()
file.close()

--throw lines in a table
local tLines = {}
for line in filedata:gmatch('.-n') do
 table.insert(tLines,line)
end

--set up function for deleting specified line
--make it so that it can take multiple lines to delete
local function deleteLine(...)
 if type(arg[1]) == 'table' then
  for _,v in pairs(arg[1]) do
   table.remove(tLines,v)
  end
 else
  for _,v in pairs(arg) do
   if type(v) == 'number' then
    table.remove(tLines,v)
   end
  end
 end
end

--delete lines as you please
deleteLine(1,2,3)

--rewrite all of the lines (assuming you haven't redefined the file variable)
file.open('w')
local s = ''
for _,v in pairs(tLines) do
 s = s..v
end
file.write(s)
file.close()

[Grim Reaper]

One method that I thought fairly quickly would be to split the file into a table by lines. You could use the split method provided at http://lua-users.org/wiki/SplitJoin

-- Compatibility: Lua-5.1
function split(str, pat)
   local t = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pat
   local last_end = 1
   local s, e, cap = str:find(fpat, 1)
   while s do
	  if s ~= 1 or cap ~= "" then
  table.insert(t,cap)
	  end
	  last_end = e+1
	  s, e, cap = str:find(fpat, last_end)
   end
   if last_end <= #str then
	  cap = str:sub(last_end)
	  table.insert(t, cap)
   end
   return t
end

With the above method, we can split a string by the passed pattern into a table of every instance.

We can now split by the end line character: "n"

The file that we want to remove line 5 from: myFile

This
is
a
sexy
test!

The code we'll write to delete line 5: 'sexy'

local tLines = {}
local nLine = 5 -- Say we don't want line 5.'
local file = fs.open( "myFile", "r" )
local fileContents = file.readAll()
file.close()

-- Compatibility: Lua-5.1
function split(str, pat)
   local t = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pat
   local last_end = 1
   local s, e, cap = str:find(fpat, 1)
   while s do
	  if s ~= 1 or cap ~= "" then
  table.insert(t,cap)
	  end
	  last_end = e+1
	  s, e, cap = str:find(fpat, last_end)
   end
   if last_end <= #str then
	  cap = str:sub(last_end)
	  table.insert(t, cap)
   end
   return t
end

tLines = split( fileContents, "n" ) -- Split the file string into a table by lines.
local sFile = "" -- This will be the appended file.

for index,value in ipairs( tLines ) do
  if index ~= nLine then -- If we're not on line 5.'
	sFile = sFile .. value .. "n" -- Read the next line in and add an end line character to it.
  end
end

file = fs.open( "myFile", "w" )
file.write( sFile ) -- Write the new contents into the file.
file.close()

The newly appended file: myFile

This
is
a
test!

Hope I helped! />

[lieudusty]

Thanks guys!