A process handles periodic tasks, and each time it does, it spits out some telemetry. The telemetry gets written off into a file each time. This process could be any of a number of interesting things: a procmail script doing something with incoming email, a Twitter-bot responding to searches, an IRC-bot responding to events, or whatever. The only important thing in this case is that it creates a variable number of log files each day, and the log files all get dumped into a single directory.

Before long, the log directory will be filled with thousands of files, and will be unmanageable. But, for some reason, we want to keep all these logs, and maybe actually use them. So the key is a script to move the logs into sub-directories based on date.

It turns out it’s easy to write a bash script to create directories in a YYYY-MM format, and move the files into them appropriately. The key is in the stat command. Conveniently, the implementation of this command is completely different and incompatible between Mac OS/BSD and Linux. Jesus H. Christ.

Linux:

#!/bin/bash
for i in *.log
do
filemonth=`stat --format=%y $i | cut -c 1-7`
mkdir -p $filemonth
mv $i $filemonth/$i
done


In Linux, the stat command will give you the data in an ISO format, and using the cut command, you can extract YYYY-MM information. The -p flag to mkdir makes it silently exit without complaining if a directory by that name already exists.

MacOS (or presumably other BSDs):

#!/bin/bash
for i in *.log
do
filemonth=`stat -f%Sm -t %Y-%m $i`
mkdir -p $filemonth
mv $i $filemonth/$i
done


In this case, we’re telling stat that we want the modified date as a string, and we specify the time format.

Either of these would be easy to modify to single day resolution (changing which columns you cut in the Linux version, or the timestamp format in the Mac version).