Variable in a path

[Steve505 0]

Hey there!

I'm working on a program similar to the database but I've find out problem I couldn't figure out...

Program should ask for code name (which'll be file name), information about code name, date and time of saving etc. But how I can insert variable in io.open()? Code now looks like this:

...
print("Enter command:")
print("")
if io.read() == "add" then
print("Enter item location:")
LOC = io.read()
f = io.open("/WH/db/"LOC, "w") -- This is the problem, LOC (variable, as seen above) should be future file name...
print("Enter information:")
CONT = term.read()
f:write(CONT)
f:close()
...

Thanks for help,

Steve505

[CptMercury 6]

Hey

If you want to insert a variable into a existing string, you can use the concat operator .. (2 dots).

io.open("/WH/db/"..LOC, "w")
-- # this will create a string that starts with /WH/db/ and ends with the string contained by LOC

 

[Steve505 0]

Oh... That's pretty easy, I was expected something more difficult.

Thank you for help, code is now working perfectly.

Steve505

EDIT: I've found another two problems:

1. Can I use io.open():read() only on specific line of a file?
2. Is there a way of printing io.open():read() without quotations? E.g. when the file contains text She sells sea shells..., mentioned code'll print on the screen "She sells sea shells", and I want to remove these quotation marks.

[CptMercury 6]

You can use io.open(path):read() to read a specific line, but only indirectly. But it might be easier to use the iterator io.lines(path).

-- # use io.read to get the whole file, it returns a string; then use string.gmatch/string.match to extract the specific line
-- # Examples:
-- # Ex1: get line 5
local path = "/somepath"
local count = 1
local targetline = 5
local file = io.open(path):read("*all")

for line in file:gmatch("[^\n]+") do
  if count == targetline then return line end
  count = count + 1
end

-- # Ex2: find line starting with #
local path = "/somepath"
local indicator = "#"
local file = io.open(path):read("*all")

return file:match("["..indicator.."][^\n]+")

-- # io.lines iterator, returns new line whenever it's called
-- # Examples:
-- # Ex1: get line 5
local path = "/somepath"
local count = 1
local targetline = 5

for line in io.lines(path) do
  if count == targetline then return line end
  count = count + 1
end

-- # Ex2: find line starting with #
local path = "/somepath"
local indicator = "#"

for line in io.lines(path) do
  if line:sub(1, #indicator) == indicator the return line end
end

 

I only got quotation marks in the  string returned by io.open():read() when I just ran io.open():read() in the Lua prompt; when I used print(io.open():read()) or io.write(io.open():read()) it printed the string without quotation marks in the output.

 

[Gorzoid 10]

I would not recommend doing io.open():read() or write(), you are never closing the file so you can't guarantee the handle is released. Make a custom function to readall/writeall quickly if you need to.

Also filesystem.concat might be better than just using "WH/db/"..LOC