From e39fdea1257a3addca1c6c20860c82dfa98ad7cc Mon Sep 17 00:00:00 2001
From: David Vazgenovich Shakaryan <dvshakaryan@gmail.com>
Date: Sat, 3 Oct 2026 00:48:59 -0700
Subject: add interval offset option

---
 backomp | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/backomp b/backomp
index 022665d..af44f77 100755
--- a/backomp
+++ b/backomp
@@ -160,11 +160,11 @@ ssh_run() {
 	fi
 }
 
-current() {
-	local str="${1}" interval="${2}"
-	local s=0 val d
+parse_duration() {
+	local str="${1}"
+	local s=0 val
 
-	while [[ "${interval}" =~ ([0-9]+)(.?) ]]; do
+	while [[ "${str}" =~ ([0-9]+)(.?) ]]; do
 		val="${BASH_REMATCH[1]}"
 		case "${BASH_REMATCH[2]}" in
 			d) ((s += val * 24*60*60)) ;;
@@ -173,12 +173,21 @@ current() {
 			*) ((s += val)) ;;
 		esac
 
-		interval="${interval#*"${BASH_REMATCH[0]}"}"
+		str="${str#*"${BASH_REMATCH[0]}"}"
 	done
+	echo "${s}"
+}
+
+current() {
+	local str="${1}" interval="${2}" offset="${3}"
+	local s o d
+
+	s="$(parse_duration "${interval}")"
 	((s < 1)) && return 1
+	o="$(parse_duration "${offset}")"
 
 	d="${str:0:10} ${str:11:2}:${str:13:2}:${str:15:2}"
-	(($(date -u +%s) / s == $(date -ud "${d}" +%s) / s))
+	((($(date -u +%s) - o) / s == ($(date -ud "${d}" +%s) - o) / s))
 }
 
 exists() {
@@ -354,8 +363,8 @@ prune() {
 
 backup() {
 	local src_path="${1}" dest_dir="${2}"
-	local retain="${3}" interval="${4}" week_start="${5}"
-	local rsync_flags="${6}" rclone_flags="${7}" ssh_flags="${8}"
+	local retain="${3}" interval="${4}" offset="${5}" week_start="${6}"
+	local rsync_flags="${7}" rclone_flags="${8}" ssh_flags="${9}"
 	local dest_path snaps keep
 
 	if ((!NO_BACKUP)) && [[ ! -e "${src_path}" ]]; then
@@ -371,7 +380,8 @@ backup() {
 		|| return 1
 
 	if ((!NO_BACKUP)) && ( [[ -z "${snaps}" ]] ||
-			! current "${snaps[0]##*/}" "${interval}" ); then
+			! current "${snaps[0]##*/}" "${interval}" \
+				"${offset}" ); then
 		dest_path="${dest_dir}/$(date -u '+%Y-%m-%d-%H%M%S')"
 		copy "${src_path}" "${dest_path}" "${snaps[0]}" || return 1
 		snaps+=("${dest_path}")
@@ -402,6 +412,7 @@ backup() {
 declare -A def_opts=(
 	['retain']= # e.g. *h or 24h7d4w12M5y or 24^h10d*M
 	['interval']='0'
+	['offset']='0'
 	['week_start']='mon' # empty value aligns weeks to 1st of each month
 	['rsync_flags']='-a'
 	['rclone_flags']='--sftp-copy-is-hardlink'
@@ -537,6 +548,7 @@ while IFS= read -r line; do
 	backup "${src}" "${dest}" \
 		"${opts['retain']}" \
 		"${opts['interval']}" \
+		"${opts['offset']}" \
 		"${opts['week_start']}" \
 		"${opts['rsync_flags']}" \
 		"${opts['rclone_flags']}" \
-- 
cgit v1.3.1