From 1eaeadf7c8cdf74f1d8edf6e892e408f4d98662d Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Wed, 10 Jun 2020 22:22:22 +0200
Subject: update

---
 bin/backup-clean | 40 ++++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 16 deletions(-)

(limited to 'bin/backup-clean')

diff --git a/bin/backup-clean b/bin/backup-clean
index 5034c44..fba4279 100755
--- a/bin/backup-clean
+++ b/bin/backup-clean
@@ -1,32 +1,40 @@
 #!/bin/sh
 # backup garbage collector
-# keep:
-#   1 backup per year the previous years
-hd=3600		# hour duration:  60s * 60
-h12=43200	# 12h
-dd=86400	# day duration:   hd * 24
-wd=604800	# week duration:  dd * 7
-md=2592000	# month duration: dd * 30
-yd=31557600	# year duration:  dd * 365.25
+[ "$USER" = root ] || exec sudo "$0" "$@"
+
+# Durations, in number of seconds.
+hd=3600	    # hour duration:  60s * 60
+h12=43200   # 12h: hd * 12
+dd=86400    # day duration:   hd * 24
+wd=604800   # week duration:  dd * 7
+md=2592000  # month duration: dd * 30
+yd=31557600 # year duration:  dd * 365.25
 
 now=$(date +'%Y%m%d_%H%M%S')
 
+# The following works only for busybox date, not coreutils
+# Kept for reference only.
 #date2ts() { d=${1%_*} t=${1#*_}; date -d "$d${t%??}" +%s; }
+
+# Convert date to timestamp, using date from GNU coreutils,
+# works also with busybox date.
 date2ts() {
-	t=$1; r=${t#????}; Y=${t%$r}
-	t=$r; r=${t#??}; m=${t%$r}
-	t=$r; r=${t#??}; d=${t%$r}
-	t=${r#_}; r=${t#??}; H=${t%$r}
-	t=$r; r=${t#??}; M=${t%$r}
-	S=${t#??}
+	t=$1; r=${t#????}; Y=${t%$r}   # Year (with century)
+	t=$r; r=${t#??}; m=${t%$r}     # Month
+	t=$r; r=${t#??}; d=${t%$r}     # Day
+	t=${r#_}; r=${t#??}; H=${t%$r} # Hour
+	t=$r; r=${t#??}; M=${t%$r}     # Minute
+	S=${t#??}                      # Second
 	date -d "$Y-$m-$d $H:$M:$S" +%s
+	#date -jf "%Y-%m-%d %H:%M:%S" "$Y-$m-$d $H:$M:$S" +%s  # BSD, MacOSX
 }
 
 ts2date() { date -d "@$1" +'%Y%m%d_%H%M%S'; }
 
 tsn=$(date2ts "$now")
 
-# minimal retention delay, according to backup age
+# Minimal retention delay in seconds, according to backup age,
+# implemented using POSIX shell arithmetic.
 retention_delay() {
 	d=$((tsn - $1))
 	if [ $((d < h12)) = 1 ]; then
@@ -54,7 +62,7 @@ while getopts :nv opt; do
 done
 shift $((OPTIND - 1))
 
-# sorted list of backups, most recent first
+# Sorted list of backups, most recent first
 dest=${1:-/.history}
 lbu=$(ls -rv "$dest")
 for d in $lbu; do
-- 
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