Trouble with the io API

Here is my code. I am trying to make a login system (the passwords and such will be encrypted don't worry). I was just testing to see that all the users where saved, but when this prints it only prints the last user. Does anyone have any idea why it did that because I cannot figure it out?

It looks like the problem is that you're opening your files for writing when you should probably be opening them for appending. When you open a file for writing ("w") the entire file is overwritten.

Try something like this - it will open for writing if the file doesn't exist and open for appending if the file already exists…

users = io.open(usersDir, fs.exists(usersDir) and "a" or "w")
pass = io.open(passDir, fs.exists(passDir) and "a" or "w")

Can I open for appending without first opening for writing?

Dog, on 03 December 2014 - 01:26 AM said:

It looks like the problem is that you're opening your files for writing when you should probably be opening them for appending. When you open a file for writing ("w") the entire file is overwritten.

Try something like this - it will open for writing if the file doesn't exist and open for appending if the file already exists…

users = io.open(usersDir, fs.exists(usersDir) and "a" or "w")
pass = io.open(passDir, fs.exists(passDir) and "a" or "w")

I had just asked if that would work for writing, but I was waiting for a moderator to approve it :P/>/> . Thanks for the help.

Also, do you know how I could get each line without the newline, write now it prints with the newline, but when I'm doing the login function I would like it to not have the newline

You never want to open an empty file in append mode, if that's what you're asking. "Append" means "add on to the end". If you've never first written something to your file, then what are you going to append to?

Certain versions of ComputerCraft will, if you attempt to open a non-existent file in "append" mode, auto-open them in "write" mode instead. Other versions won't open the file at all. The code Dog's suggesting solves that particular problem by manually checking whether the file exists and specifically selecting the appropriate mode.

I'm not sure what you mean by the "newline" stuff. I can tell you the "print" function always performs a line break after whatever it outputs, whereas the "write" function does not.

Yes, you can open for appending without first opening for writing :)/>

As for writing each line, you could try replacing write with writeLine, but you may have to change your syntax (e.g. users.writeLine(…) instead of users:writeLine(…\n) - note the dot instead of the colon).

EDIT: :ph34r:/> 'd by BB

I like BB's suggestion of using print instead of write - keeps it simple.

I was asking how I could get it without the newline :P/>, but I thought the print function didn't add a newline. Armed with that info I think I'm ready to start making this system.