Script to delete time machine backups older than 1 year from all backup disks. Needs sudo permissions

deleteOldTimeMachineBackups.sh

#!/bin/bash

# Calculate the cutoff date (1 year ago)
cutoff_date=$(date -v-1y "+%Y-%m-%d-%H%M%S")

echo "cutoff_date => $cutoff_date"

# find mount points
output=$(sudo tmutil destinationinfo)

# Initialize an empty array to store mount points
mount_points=()

# Use awk to extract the lines containing "Mount Point"
while IFS= read -r line; do
    if [[ $line =~ "Mount Point" ]]; then
        mount_point=$(echo "$line" | awk -F': ' '{print $2}')
        mount_points+=("$mount_point")
    fi
done <<< "$output"

echo "mount_points => ${mount_points[*]}"


# Gather backup timestamps for deletion
for mount_point in "${mount_points[@]}"; do
    # Initialize a string to store timestamps
    backup_timestamps=()
    # Gather backups from last calendar year excluding the latest
    backups=$(sudo tmutil listbackups -d "$mount_point" | sort -n)

     SAVEIFS=$IFS   # Save current IFS (Internal Field Separator)
     IFS=$'\n'      # Change IFS to newline char
     backups=($backups)
     IFS=$SAVEIFS   # Restore original IFSIFS=$'\n'

    # Iterate through the dates and keep only those on or after the cutoff date
    for date in "${backups[@]}"; do
       if [[ $date < $cutoff_date ]]; then
          backup_timestamps+=("-t $date ")
       fi
    done

    #echo "backup_timestamps => ${backup_timestamps[*]}"

    # Delete all gathered backups in a single command
    if [[ -n "$backup_timestamps" ]]; then
       echo sudo tmutil delete -d "$mount_point" "${backup_timestamps[@]}"
       sudo tmutil delete -d "$mount_point" "${backup_timestamps[@]}"
       #echo "Deleted backups with timestamps:$backup_timestamps"
    else
       echo "No backups to delete."
    fi

done