#!/bin/sh -
#
#   Copyright (C) 2007 by Oliver Fromme <olli@fromme.com> <olli@secnetix.de>
#
#   adjtouch -- modify the mtime of files, similar to touch(1).
#               However, in contrast to touch(1), the existing
#               mtime is adjusted by a given amount.
#               Please refer to description of the "-v" option
#               of date(1), because this script uses it!
#
#   Example:  "adjtouch -v +1H *"  increases the mtime of all
#   files in the current directory by one hour.
#
#   Important:  This script uses FreeBSD-specific features, so
#   it works only on FreeBSD.
#

Usage()
{
	echo "Usage:  ${0##*/} -v <adjust> ... <file> ..." >&2
	echo "Please read the date(1) manual page for details on the -v option." >&2
	exit 1
}

while :; do
	case "$1" in
		-v)
			ADJ_ARGS="$ADJ_ARGS -v $2"
			shift 2
			;;
		-v*)
			ADJ_ARGS="$ADJ_ARGS $1"
			shift
			;;
		--)
			shift
			break
			;;
		-)
			Usage
			;;
		*)
			break
			;;
	esac
done

if [ $# -lt 1 ]; then
	Usage
fi

#   The following shell code looks unnecessarily complicated,
#   but it's written this way for a reason!
#   We don't use a "while read" loop because it would break
#   for file names that contain spaces or tabs.  On the other
#   hand, we don't have to use xargs(1) for the stat(1) call
#   because the arguments will always fit, because this shell
#   script was called with the same arguments after all.

stat -f%m "$@" \
| for n in "$@"; do
	read t
	d=$(date -r $t $ADJ_ARGS +"%Y%m%d%H%M.%S") \
	    || break
	touch -t $d "$n"
done

#--