#!/bin/sh
#
# $Id: msort,v 1.2 1996/10/21 19:48:06 vogelke Exp $

PATH=/bin:/usr/bin:/usr/local/bin
export PATH

USAGE='
   msort:   sorts multiline records of varying lengths.
            Author:  Susan Andarmani, January 91 UnixWorld.

   Usage:  msort [-r line] [file]
           msort [-rline] [file]

   Where:  "line"  is the record number in each group of
                   records on which the sort is to be done.
                   Each group of records is delimited by a
                   blank line.  "line" defaults to 1.

           "file"  is the file to be sorted.  If no file is
                   entered, stdin is used.

   Examples:       msort -r 4 file
                   msort -r3 file
                   cat file | msort -r1
'

#
# Handle command line options.
# Sort on the first line by default.
#

SORTLINE=1

while :
do
    case "$1" in
        --)  shift; break ;;
        -r)  SORTLINE="$2"; shift; shift ;;
        -r*) SORTLINE=`echo "$1" | sed 's/^..//'`; shift ;;
        -*)  echo "$USAGE" >& 2; exit 1 ;;
        *)   break ;;
    esac
done

#
# Handle remaining arguments.
#

case "$#" in
    0)  INFILE="" ;;
    1)  INFILE="$1" ;;
    *)  echo "$USAGE" >& 2; exit 1 ;;
esac

#
# Convert the sort line to a field number, and process the data.
#

SORTFIELD=`expr $SORTLINE - 1`

(cat $INFILE; echo) | sed -n '
1 {
/^$/d
}
: top
N
s/\n\(..*\)/@\1/g
t top
s/\n/@/p' | sort -t@ +$SORTFIELD | tr '@' '\012'
 
exit 0