you could just add an additional integer to your filename, so it will be unique. if you start with 0 and go up, you even have the real order.

generate the filename, test if a file allready exists with this if not create one... you don't need locking for that.

Process 1 checks for filename XXX-42, doesn't exist
Process 2 checks for filename XXX-42, doesn't exist
Process 1 creates filename XXX-42 and starts writing to it
Process 2 opens filename XXX-42 and starts writing to it
Process 1 finishes writing to XXX-42
Process 2 finishes writing to XXX-42
[download]

You are correct about this. You have to look that File XX-42, but the other process don't have to wait until the process which has opened XX-42 finishs. This was part of his question.

If I dont lock the 'counter number holder file thingy' and two occurances of the cli access the 'counter number holder file thingy', each occurance of the script will get the same number.. hence the requirement to lock the 'counter number holder file thingy'.

I do agree though that I might need to look at a database.

Maybe just append a random number, lock it successfully, or try another.

Maybe just append a random number

Or maybe not.

The OP states that the names must be in sequence. Consider two files created in the epoch second 1090225457. The first file is generated with the rand string 0.837 (rounded). Half a second later, still in the same epoch second, another file is created, and rand returns 0.238 (rounded). The second file will sort before the first...

The same critism can be made of beable's solution elsewhere in this thread.

- another intruder with the mooring of the heat of the Perl