Vwwxrf

I want your suggestions about this script. I use it to backup configuration of softwares installed on my home media server.

What improvements would you do?

thanks you for any inputs.

#!/bin/bash

# ==================================================================================
# Description: BackUp script following a Hanoi scheme using rsync.
# Author: Hugo Lapointe Di Giacomo
# ==================================================================================

set -o errexit
set -o nounset
#set -o xtrace

# ----------------------------------------------------------------------------------
# Options
# ----------------------------------------------------------------------------------
setsMax=16 # ................................ Maximum number of sets bakcup.
cmdPrefix="" # .............................. "echo" if dry-run enable, "" otherwise.
srcDir="/appdata" # ......................... Source directory to backup.
dstDir="/mnt/backup/snapshots" # ............ Destination directory to backup in.
logDir="/mnt/backup/logs" # ................. Logs directory.


# ----------------------------------------------------------------------------------
# Constants
# ----------------------------------------------------------------------------------
SEC_PER_DAY=86400; # ........................ Number of seconds per day.
LATEST_SNAP="$dstDir/latest"; # ............. The "latest" snap.
LATEST_LOG="$logDir/latest"; # .............. The "latest" log.
DATE_FORMAT="%Y-%m-%d"; # ................... The format of a date.
HOUR_FORMAT="%H:%M"; # ...................... The format of a hour.


# ----------------------------------------------------------------------------------
# Show usage of this script.
# ----------------------------------------------------------------------------------
function showUsage() 
 echo "Usage: $0 [OPTIONS]..."
 echo ""
 echo "Options available:"
 echo " -h, --help Show usage of the script."
 echo " -m, --max Maximum sets of backup."
 echo " -s, --src Source directory to backup."
 echo " -d. --dst Destination directory to backup in."
 echo " -l, --log Log directory."
 echo " -r, --dry Enable dry-run."



# ----------------------------------------------------------------------------------
# Parse arguments.
# ----------------------------------------------------------------------------------
function parseArgs() --help)
 showUsage $@
 exit 0
 ;;

 -m


# ----------------------------------------------------------------------------------
# Create a backup with rsync.
# ----------------------------------------------------------------------------------
function createBackUp() tee "$logFile"


# ----------------------------------------------------------------------------------
# Update the latest links.
# ----------------------------------------------------------------------------------
function updateLatestLinks() 
 $cmdPrefix rm -f "$LATEST_SNAP"
 $cmdPrefix ln -s "$snapDir" "$LATEST_SNAP"

 $cmdPrefix rm -f "$LATEST_LOG"
 $cmdPrefix ln -s "$logFile" "$LATEST_LOG"


# ----------------------------------------------------------------------------------
# Calculate the previous move in the cycle.
# https://en.wikipedia.org/wiki/Backup_rotation_scheme
# ----------------------------------------------------------------------------------
function calculateDaysFromBackupOfSameSet() 
 local todayInSec=$(date +%s)
 local todayInDay=$(($todayInSec / $SEC_PER_DAY))

 local daysToBackup=$((2 ** ($setsMax - 1))) 

 local daysElapsed=0
 local i=1

 while [ $i -lt $(($daysToBackup / 2)) ]; do
 local rotation=$(($todayInDay & $i))

 if [ $rotation -eq 0 ]; then
 daysElapsed=$(($i * 2))
 break
 fi

 daysElapsed=$(($daysToBackup / 2))
 i=$((2 * $i))
 done

 echo $daysElapsed



# ----------------------------------------------------------------------------------
# Main function.
# ----------------------------------------------------------------------------------
function main() 
 parseArgs $@

 local todayDatetime=$(date +$DATE_FORMAT.$HOUR_FORMAT)

 if createBackUp $todayDatetime; then
 updateLatestLinks

 local daysElapsed=$(calculateDaysFromBackupOfSameSet)
 local expiredDay=$(date -d "$daysElapsed days ago" +$DATE_FORMAT)
 $cmdPrefix rm -frv "$dstDir/$expiredDay."*
 fi


main $@