Older == Not Newer

Quite often we need to clean up old files in directory, but the criteria is often based on ctime/atime/mtime in find with unit in days. In certain situation, this may not be fine-grain enough to locate files. In find, you can specify the -newer flag to locate files newer than the file reference. However, find does not have -older. What you can do is to specify 'not newer' to represent 'older':
\( ! -newer reference \)

Here I created a lot of files (4320) with file name based on time stamp and tried to use this trick to delete files older than the reference (log-200912301450). See my previous post in how I use the -newer flag too.

# yr=2009

# for mth in `seq -w 7 12`
do
    for day in `seq -w 1 30`
    do
        for hr in `seq -w 2 6 24`
        do
                for min in `seq -w 0 10 50`
                do
                        touch -t $yr$mth$day$hr$min log-$yr$mth$day$hr$min
                done
        done
    done
done

# ls | wc -l
4320

# ls -lrt | head
total 0
-rw-r--r-- 1 root root 0 2009-07-01 02:00 log-200907010200
-rw-r--r-- 1 root root 0 2009-07-01 02:10 log-200907010210
-rw-r--r-- 1 root root 0 2009-07-01 02:20 log-200907010220
-rw-r--r-- 1 root root 0 2009-07-01 02:30 log-200907010230
-rw-r--r-- 1 root root 0 2009-07-01 02:40 log-200907010240
-rw-r--r-- 1 root root 0 2009-07-01 02:50 log-200907010250
-rw-r--r-- 1 root root 0 2009-07-01 08:00 log-200907010800
-rw-r--r-- 1 root root 0 2009-07-01 08:10 log-200907010810
-rw-r--r-- 1 root root 0 2009-07-01 08:20 log-200907010820

# ls -lrt | tail
-rw-r--r-- 1 root root 0 2009-12-30 14:20 log-200912301420
-rw-r--r-- 1 root root 0 2009-12-30 14:30 log-200912301430
-rw-r--r-- 1 root root 0 2009-12-30 14:40 log-200912301440
-rw-r--r-- 1 root root 0 2009-12-30 14:50 log-200912301450
-rw-r--r-- 1 root root 0 2009-12-30 20:00 log-200912302000
-rw-r--r-- 1 root root 0 2009-12-30 20:10 log-200912302010
-rw-r--r-- 1 root root 0 2009-12-30 20:20 log-200912302020
-rw-r--r-- 1 root root 0 2009-12-30 20:30 log-200912302030
-rw-r--r-- 1 root root 0 2009-12-30 20:40 log-200912302040
-rw-r--r-- 1 root root 0 2009-12-30 20:50 log-200912302050

# find . \( ! -newer log-200912301450 \) -type f -exec rm -f {} \;

# ls -lrt
total 0
-rw-r--r-- 1 root root 0 2009-12-30 20:00 log-200912302000
-rw-r--r-- 1 root root 0 2009-12-30 20:10 log-200912302010
-rw-r--r-- 1 root root 0 2009-12-30 20:20 log-200912302020
-rw-r--r-- 1 root root 0 2009-12-30 20:30 log-200912302030
-rw-r--r-- 1 root root 0 2009-12-30 20:40 log-200912302040
-rw-r--r-- 1 root root 0 2009-12-30 20:50 log-200912302050