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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()
deleteList = list.getSubList(100, end) // from, to

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.

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up vote 5 down vote accepted

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)

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Small typo: use head -n 100 instead of head -n -100. – chronos Aug 29 '10 at 15:28
Thanks. I'm running this from a cronjob. How do I get full paths? – nbolton Aug 29 '10 at 15:29
This is not a typo, the ls is -rt so we need -100 to tell head to get rid of the 100 newest lines/files! To set full paths, simply put it in the ls, for instance ls -rt /my/path/to/dir | head -n -100. For cron, ls ... should better have their full path. Please see my edit above. – ringø Aug 29 '10 at 15:40
Use xargs instead, or files may not be handled as you expect (for example, spaces): ls -rt | head -n -100 | xargs rm -f – Andrew M. Aug 29 '10 at 15:45
Good catch, and +1 for completeness. – Andrew M. Aug 29 '10 at 16:32

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

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I'm not sure how I'd use logrotate to do this. Baring in mind that I don't want to rename the files or delete them after each file name has been rotated x number of times. Please give an example of how logrotate could do the same thing as ring0's example. – nbolton Aug 30 '10 at 18:33

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