Shell script to compress directories more than 10 weeks old, using AFSC tool

compress_old_dirs.sh

# MacOS has on-the-fly decompression, but not on-the-fly compression.
# AFSC tool https://github.com/RJVB/afsctool.git is handy
# for applying compression, but if you're actively working
# on something, you'll be writing new files, meaning stuff won't stay.
# compressed.  Even saving a new
# version of a file from an application usually means a brand
# new (uncompressed) file. 

# Also, directories containing compressed files like jpg images
# or movies won't benefit from file system level compression.

# What I do is run this script on occasion in a folder that 
# I know contains a lot of subfolders of potentially compressible
# files. It compresses the entire subfolder if it's older than 6 million seconds (
# about 10 weeks)

# I use brew to install AFSCTool into /usr/local/bin, and schedule
# this shell script to run as a LaunchDaemon once a week in the higher
# level directory.  For example, you could run it in your Documents folder 
# once a week.  

export PATH=/usr/local/bin:$PATH
now="$(date +%s)"
find . -maxdepth 1 -mindepth 1 -type d -print0 |
    while IFS= read -r -d '' line; do 
        dirdate="$(stat -f %m $line)"
        # echo $now
        # echo $dirdate
        let diff="${now} - ${dirdate}"
        echo "Seconds since directory $line modified is $diff"
        if [ "$diff" -gt 6000000 ]; then
           echo "Compressing $line"
           afsctool -c -j1 -6 "$line"
        fi
    done