Updating a flat file database

Does XML count as a flat-file database?

Maybe, but I am using a .txt file (you know that)

I have only a week or so left for this project, any one have any idea how to do it?

Maybe? I didn't know it was a .txt file -- does it have to be one?

What environment is this? Do you have PHP XML libs? expat, sablotron?

How are you creating your flat files?
Are you using php, asp or pearl?

If you show me the code you use to create and read from the db, I can show you how to update it.

Abhishek Reddy, I've never used XML so I'm not sure but, there are quite a lot of tutorials on how to convert flat files to XML so they don't seem to be the same thing. Sounds like XML is a step up.

This is how I am reading the db:

Abhishek, KarenArt: I am using PHP to do this

I believe what you're looking for is fwrite.

I was going to post some code for you, but these pain pills have me so messed up I doubt if I'd get it right.

There is a really good explination of fwrite at http://us3.php.net/fwrite

Here's a full tutorial on working with flat files http://www.spoono.com/php/tutorials/tutorial.php?id=32 This should explain what each part of the code does.

If that doesn't work for you, let me know and I'll try to post the code for you.

Have fun with it!

Thanks for the links KarenArt, I had a look at them but it still doesn't tell me up to update the flat-file :S

Perhaps I am not making myself clear...

Say I have the following in my db.txt file:

And I would like to change it to this:

How would I do that?

First, init the "database": read the file line-by-line into an array; split each array item by "||" so it becomes a multidimensional array, as though it were a result returned by a MySQL 'SELECT *'.

From there, use PHP to alter array element values as needed.

Last, reconstruct the whole file from the array you have.

The reading of the whole file, then writing it all again is what causes extra server overhead with flat-file databases. This, I believe, can be circumvented if you use self-aware, flat documents (i.e. XML), so data fields can be located and modified easily -- even using another layer of abstraction (XML libs). Although, Karen might be right about the distinction between XML and flat-file. Again, are you restricted from using XML?

Alternatively, you could look into PHP dba. I've never used it, but it looks like it handles flat-file databases too.

Yes, I think I am restricted from using XML. I can easily have it on my computer, don't know about the school or host though. Besides, if I get into XML, it'll take me a while to figure everything out and get used to it - no matter how easy it seems. I don't have that much time left or I probably will try XML. :S

I got that far but I don't know the actual code to do it, I am still very new to arrays and databases. What functions do I acutally use to achieve it? Can any one produce any code? Someone put me out of my misery! lol

Read the comments on the filesystem functions pages... Use explode() to split the strings. Meddle with the values as you would any basic array variable. Write to the file as explained in the fwrite() PHP doc... it is really basic.

Use file_get_contents() to read the contents of the file into a string.

explode("\n",$db_string) it to create an array containing lines (records) of the database.

explode("||",$db_string[$i]) in a foreach{} or other loop to recursively split each record into fields.

Now you can access each element via $db_string[y][x] -- this is how you alter the values.

Once that's done, loop through the whole array, reconstructing the database string, perhaps using implode(). fwrite() or file_put_contents() that back into the file, not appending but overwriting.

Eh! I must be really stupid or I really do not understand, any one have any code they can show me as an example?

No guarantees, it is untested, may need tweaking. Try it.