From 079373281d9db7f0dd7fc6a53fcabc773ac95e4c Mon Sep 17 00:00:00 2001
From: David Vazgenovich Shakaryan <dvshakaryan@gmail.com>
Date: Mon, 9 Feb 2026 23:03:21 -0800
Subject: use AWK to prefilter and sort input

For the two-array deletion loop, it is vital that the output sort order
be the reverse of the input sort order. It's unlikely to matter given
the generated directory names, but using AWK for both is safer than
using `sort' for the input.
---
 backomp | 40 ++++++++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 10 deletions(-)

diff --git a/backomp b/backomp
index 0580750..c56396e 100755
--- a/backomp
+++ b/backomp
@@ -2,7 +2,19 @@
 
 set -e
 
-! read -rd '' FILTER_AWK <<'EOF'
+! read -rd '' AWK_PREFILTER <<'EOF'
+/(\/|^)[0-9]{4}-[0-9]{2}-[0-9]{2}-[0-9]{6}$/ {
+	a[$0]
+}
+
+END {
+	n = asorti(a)
+	for (i = n; i >= 1; --i)
+		print a[i]
+}
+EOF
+
+! read -rd '' AWK_FILTER <<'EOF'
 function flr(n, s) {
 	return int(n / s) * s
 }
@@ -31,12 +43,16 @@ BEGIN {
 }
 
 NR == 1 {
-	++keep[$1]
+	++keep[$0]
 }
 
 {
-	t = mktime(gensub(/(.*\/|^)(.+)-(..)-(..)-(..)(..)(..)/,
+	t = mktime(gensub(/(.*\/|^)(.+)-(..)-(..)-(..)(..)(..)$/,
 		"\\2 \\3 \\4 \\5 \\6 \\7", 1), 1)
+	if (t < 0) {
+		++keep[$0]
+		next
+	}
 
 	bt["h"] = flr(t, 60*60)
 	bt["d"] = flr(t, 24*60*60)
@@ -60,7 +76,7 @@ NR == 1 {
 			next
 
 		if ((b, bt[b]) in bkeep || ret[b] == "*" || bc[b]++ < ret[b])
-			bkeep[b, bt[b]] = $1
+			bkeep[b, bt[b]] = $0
 
 		for (j in buckets)
 			last[b, buckets[j]] = bt[buckets[j]]
@@ -90,19 +106,23 @@ backup() {
 
 	[[ "$((dcount++))" -ne 0 ]] && echo
 	echo "[${dcount}] [${retain}] ${src_path} => ${dest_dir}"
-	mapfile -t snaps < <(shopt -s nullglob;
-		printf '%s\n' "${dest_dir}/"* | sort -r | head -c -1)
+	mapfile -td $'\0' snaps < <(shopt -s nullglob;
+		printf '%s\0' "${dest_dir}/"* | awk -v 'RS=\0' -v 'ORS=\0' \
+			-- "${AWK_PREFILTER}")
 
 	dest_path="${dest_dir}/$(date -u '+%Y-%m-%d-%H%M%S')"
 	run rsync -ac --mkpath ${snaps[0]:+"--link-dest=${snaps[0]}"} \
 		"${src_path}" "${dest_path}"
-	snaps=("${dest_path}" "${snaps[@]}")
+	snaps+=("${dest_path}")
+	mapfile -td $'\0' snaps < <(
+		printf '%s\0' "${snaps[@]}" | awk -v 'RS=\0' -v 'ORS=\0' \
+			-- "${AWK_PREFILTER}")
 
-	mapfile -t keep < <(
-		awk \
+	mapfile -td $'\0' keep < <(
+		printf '%s\0' "${snaps[@]}" | awk -v 'RS=\0' -v 'ORS=\0' \
 			-v "opt_retain=${retain}" \
 			-v "opt_week_start=${week_start}" \
-			-- "${FILTER_AWK}" < <(printf '%s\n' "${snaps[@]}"))
+			-- "${AWK_FILTER}")
 	if [[ -z "${keep}" ]]; then
 		echo "WARNING: dirs to keep shouldn't be empty; skipping" >&2
 		return
-- 
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