#!/bin/ksh
#
# $Id: keep,v 1.2 2002/02/05 22:05:55 vogelke Exp $
#
# NAME:
#    keep
#
# SYNOPSIS:
#    keep [-hv] count dir [regex]
#
# DESCRIPTION:
#    Preserves the last "count" files under directory "dir"
#    which match optional regular expression "regex".
#
# OPTIONS:
#    -h, --help       print this message
#    -v, --version    print the version and exit
#
# AUTHOR:
#    Based on Free Software Foundation configure scripts.
#
#    Karl Vogel <vogelke@dnaco.net>
#    Sumaria Systems, Inc.

PATH=/bin:/usr/sbin:/usr/bin
export PATH
umask 022
tag=`basename $0`

# ======================== FUNCTIONS =============================
# die: prints an optional argument to stderr and exits.
#    A common use for "die" is with a test:
#         test -f /etc/passwd || die "no passwd file"
#    This works in subshells and loops, but may not exit with
#    a code other than 0.

die () {
    echo "$tag: error: $*" 1>&2
    exit 1
}

# usage: prints an optional string plus part of the comment
#   header (if any) to stderr, and exits with code 1.

usage () {
    lines=`egrep -n '^# (NAME|AUTHOR)' $0 | sed -e 's/:.*//'`

    (
        case "$#" in
            0)  ;;
            *)  echo "usage error: $*"; echo ;;
        esac

        case "$lines" in
            "") ;;

            *)  set `echo $lines | sed -e 's/ /,/'`
                sed -n ${1}p $0 | sed -e 's/^#//g' |
                    egrep -v AUTHOR:
                ;;
        esac
    ) 1>&2

    exit 1
}

# version: prints the current version to stdout.

version () {
    lsedscr='s/RCSfile: //
    s/.Date: //
    s/,v . .Revision: /  v/
    s/\$//g'

    lrevno='$RCSfile: keep,v $ $Revision: 1.2 $'
    lrevdate='$Date: 2002/02/05 22:05:55 $'
    echo "$lrevno $lrevdate" | sed -e "$lsedscr"
    exit 0
}

# ======================== MAIN PROGRAM ==========================

# Defaults:
ac_invalid="invalid option; use --help to show usage"
count=
dir=
regex='.'
k=0

for ac_option
do
    case "$ac_option" in
        -h | -help | --help | --hel | --he)
            usage ;;
    
        -v | -version | --version | --versio |\
        --versi | --vers)
            version ;;
    
        -*) die "$ac_option: $ac_invalid" ;;

        *)  k=`expr $k + 1`
	    case "$k" in
	        1)  count="$ac_option" ;;
	        2)  dir="$ac_option" ;;
	        3)  regex="$ac_option" ;;
                *)  usage "too many args" ;;
	    esac
	    ;;
    esac
done

#
# Real work starts here.
#

case "$count" in
    "")     usage "no file count entered" ;;
    [1-9]*) count=`expr $count + 1`;;
    *)      usage "file count must be a number" ;;
esac

case "$dir" in
    "") usage "no directory entered" ;;
    *)  ;;
esac

test -d "$dir" || die "$dir: not a directory"
cd $dir

set X `ls -1t 2> /dev/null | grep "$regex" | tail +"$count"`
shift
case "$#" in
    0)  ;;
    *)  rm $* ;;
esac

exit 0