What does one do with temporary files? For things one really doesn’t
need, there’s /tmp, which is wiped on boot—though sometimes it’s a
ramdisk, and one should be wary of dropping large files into
ramdisks. But what about e.g. downloaded isos, pdfs prepared for
printing, and the like? Things one needs now, might need
tomorrow, but definitely won’t need in a year’s time?
Like most people I used to use ~/Downloads and go through it (with
ncdu) every time it got too large. But this isn’t really
satisfying: one can accumulate thousands of files each only a megabyte
in size. I considered using cron to wipe downloads ever so often,
but sometimes one wants to keep things.
The solution is a dedicated directory, ~/volatile-tmp though you can
call it what you like, and a script which scans it every day and
deletes everything older than some epoch. Whilst one could do this
directly with find, I threw together a python script which just globs
the tmpdir. Thus subdirs can be handled the way (after a lot of
thinking) I think they should be: any tree below ~/volatile-tmp has
the age of the youngest member at any depth (and we only recurse by
one level, to avoid deleting bits of projects). If need be the life
of a particular dir can be extended by dropping a file named
.volatile-tmp in it, or it can be preserved by touching .preserve.
When I was at school I put all the paperwork they give
you—worksheets, letters, etc—in a big box marked volatile, and
every month threw away the bottom half. Thus the probability that I
could find a particular piece of work diminished logarithmically as
time went on. If you use a backup system like
backintime then files have a
similar half-life: as older backups are purged (and I don’t exclude
~/volatile-tmp from backup) the chance of finding a file dwindles to
nothing. So if it goes today and you need it tomorrow it should be
findable, but in two years… which fits the original picture quite
nicely.
I call the script from a systemd unit, but cron would work just as
well. Code (and an installation script) is on
gitlab and it’s been running
for a year or so now: my ~/volatile-tmp is at time of writing only
46M in size—and I use it a lot.