#!/bin/sh
#
# Archive a log file in a separate archival area.
#	- Cameron Simpson <cs@zip.com.au> 19nov97
#

archdir=
archname=current

cmd=`basename "$0"`
usage="Usage: $cmd [-n archname] -d archdir logfile
	-d archdir	Directory in which to keep the archived data.
	-n archname	What file within the directory to append to.
			Default: $archname"

badopts=
while :
do
    case $1 in
	-d)	archdir=$2; shift ;;
	-n)	archname=$2; shift ;;
	--)	shift; break ;;
	-?*)	echo "$cmd: unrecognised option: $1" >&2; badopts=1 ;;
	*)	break ;;
    esac
    shift
done

case "$archname" in
    /*)	archdir=`basename "$archname"` ;;
    *)	if [ -n "$archdir" ]
	then  archname=$archdir/$archname
	else  echo "$cmd: missing archdir" >&2; badopts=1
	fi
	;;
esac

if [ $# = 0 ]
then  echo "$cmd: missing logfile" >&2; badopts=1
else
      logfile=$1; shift
      case $logfile in -*) logfile=./$logfile ;; esac
      [ $# = 0 ] || { echo "$cmd: extra arguments: $*" >&2; badopts=1; }
fi

# catch bad options
[ $badopts ] && { echo "$usage" >&2; exit 2; }

[ -r "$logfile" ] || { echo "$cmd: no readable file \"$logfile\"" >&2
		       badopts=1
		     }

[ -d "$archdir" ] || { echo "$cmd: no directory \"$archdir\"" >&2
		       badopts=1
		     }

# catch bad setup - give usage anyway, as a reminder
[ $badopts ] && { echo "$usage" >&2; exit 1; }

[ -s "$logfile" ] || exit 0	# nothing to save

logbase=`basename "$logfile"`
wk=.$cmd.$logbase.$$

# snapshot the log
# XXX - race condition here
cp "$logfile" "$wk" && { >"$logfile"; }

# save data - if ok, remove snapshot
{ tee -a "$archname" <"$wk" >/dev/null && rm "$wk"; } \
	|| { echo "$cmd: can't save to \"$archname, data left in $wk" >&2
	     exit 1
	   }