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I am trying to write a script that finds files that are from before September 24th, 2014, and deletes them. How would I do this?

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Create a dummy file with time set to Sept. 24 2014 00:00h, then find anything NOT newer and delete:

#date format YYYYMMDDhhmm
touch -t 201409240000 dateref
find -type f ! -newer dateref -delete

Please make yourself a bit familiar with find before using the -delete option. Note that is must be on the last position and maybe check the results without -delete beforehand.

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You can use find's -newer option with (a reference file which has that date), along with ! to negate the -newer. You can use touch -d to create the reference file. For example:

touch -d "2014-09-23 23:59:59.999999999" /tmp/reference-file
find /path/to/directory/ ! -newer /tmp/reference-file -ls

You will probably want to pipe that into less or redirect to a file for examination.

Change the -ls option to -delete after you've confirmed that it will only delete files you want deleted.

(if you don't mind also deleting files that were created exactly at midnight on 2014-09-14, you can just use touch -d 2014-09-24 - because ! -newer doesn't just mean "older than", it means "older than or equal to". The .999999999 is probably "good enough" for most purposes)

Note: the above assumes GNU versions of both find and touch. May or may not work with other versions. If you're using Linux, GNU utils are standard (unless you're using some tiny distro that uses busybox or similar to save space).

From man find:

-newer reference

Time of the last data modification of the current file is more recent than that of the last data modification of the reference file. If reference is a symbolic link and the -H option or the -L option is in effect, then the time of the last data modification of the file it points to is always used.

See also -anewer in the same man page if you want to use access times rather than modification time.

The -newerXY options are also relevant:

-newerXY reference

Succeeds if timestamp X of the file being considered is newer than timestamp Y of the file reference. The letters X and Y can be any of the following letters:

 a   The access time of the file reference
 B   The birth time of the file reference
 c   The inode status change time of reference
 m   The modification time of the file reference
 t   reference is interpreted directly as a time

Some combinations are invalid; for example, it is invalid for X to be t. Some combinations are not implemented on all systems; for example B is not supported on all systems. If an invalid or unsupported combination of XY is specified, a fatal error results.

Time specifications are interpreted as for the argument to the -d option of GNU date.

If you try to use the birth time of a reference file, and the birth time cannot be determined, a fatal error message results.

If you specify a test which refers to the birth time of files being examined, this test will fail for any files where the birth time is unknown.

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  • Note that there's nothing GNU-specific in find /path/to/directory/ ! -newer /tmp/reference-file -ls. -ls is not standard but is a common extension originally from SysV IIRC. ! -newermt 2014-09-24 is not POSIX but is from BSD, not a GNU extension either. touch -d is POSIX though you'd need 2014-09-13T23:59:59.999999999. Using touch -t is more portable. Sep 24 at 6:00
  • That's why I said "May or may not work with other versions". I don't care enough about non-GNU versions to put in the time and effort to find out. It's there only as a warning to the OP and other readers that it's non-standard and may not work on their system if it's some ancient or proprietary unix/unix-like system.
    – cas
    Sep 24 at 6:03
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Try this script:

#!/bin/bash

d2=$(date +%s)
d1=$(date -d "2014-09-24" +%s)
d=$(( (d2 - d1) / 86400 ))

find ./ -mtime +$d -delete

First, try it without -delete to make sure that the right files are found. When you are 100% sure add -delete. And use your desired path instead of ./ in find.

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