What Unix command can I use to enforce a limit of 100 files in a folder?

Question

I would like to delete the oldest files in a directory, after a limit of 100 files. In other words, I want to ensure that no more than 100 files exist in the directory, and if a limit is exceeded, delete the oldest files after the limit. I don't just want to delete files older than x days, since if this was run on a cronjob, eventually all files would be deleted.

I guess if I were to program this, the pseudo code would be:

list = dir.getFiles()
list.sortByDate()
deleteList = list.getSubList(100, end) // from, to
deleteAll(deleteList)

So what would the appropriate Unix command be? I guess find would be involved somehow with the -exec argument, but I'm not sure about the sorting/limiting aspect.

Answer 1

find should not be necessary. If you first go to the right dir,

rm -f `ls -rt | head -n -100`

to specify a path

rm -f `ls -rt /path/to/my/dir | head -n -100`

and for cron (on Ubuntu!)

/bin/rm -f `/bin/ls -rt /path/to/my/dir | /usr/bin/head -n -100`

A command path can be determined using which, e.g.

which ls

Finally, if file names contain spaces, they should be quoted ls -Q then sent to xargs

/bin/ls -Qrt /path/to/my/dir | /usr/bin/head -n -100 | /usr/bin/xargs /bin/rm -f

(tested on Ubuntu, for your tests, replace rm -f with echo to see what is to be deleted)

Answer 2

Are you reinventing the wheel called log rotation? If so, use logrotate (on linux systems; other systems will have their own equivalent programs).