Unique Linux filename, sortable by time

Question

Previously I was using uuidgen to create unique filenames that I then need to iterate over by date/time via a bash script. I've since found that simply looping over said files via 'ls -l' will not suffice because evidently I can only trust the OS to keep timestamp resolution in seconds (nonoseconds is all zero when viewing files via stat on this particular filesystem and kernel)

So I then though maybe I could just use something like date +%s%N for my filename. This will print the seconds since 1970 followed by the current nanoseconds.

I'm possibly over-engineering this at this point, but these are files generated on high-usage enterprise systems so I don't really want to simply trust the nanosecond timestamp on the (admittedly very small) chance two files are generated in the same nanosecond and we get a collision.

I believe the uuidgen script has logic baked in to handle this occurrence so it's still guaranteed to be unique in that case (correct me if I'm wrong there... I read that someplace I think but the googles are failing me right now).

So... I'm considering something like

FILENAME=`date +%s`-`uuidgen -t`
echo $FILENAME

to ensure I create a unique filename that can then be iterated over with a simple 'ls' and who's name can be trusted to both be unique and sequential by time.

Any better ideas or flaws with this direction?

Answer 1

If you order your date format by year, month (zero padded), day (zero padded), hour (zero padded), minute (zero padded), then you can sort by time easily:

FILENAME=`date '+%Y-%m-%d-%H-%M'`-`uuidgen -t`
echo $FILENAME

or

FILENAME=`date '+%Y-%m-%d-%H-%M'`-`uuidgen -t | head -c 5`
echo $FILENAME

Which would give you:

2015-02-23-08-37-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

or

2015-02-23-08-37-xxxxx
# the same as above, but shorter unique string

You can choose other delimiters for the date/time besides - as you wish, as long as they're within the valid characters for Linux file name.