Shell Programming and Scripting

#! /usr/bin/ksh

##  r-r--s
##  r-r--t

longset="[acdefghiklmnpqrstvyz]"
pattern="r${longset}r${longset}${longset}[ts]"

pos=1
linen=0
IFS=""
while read input ; do
        ((linen=linen+1))
        preamble="Line: ${linen} At position"
        input="${save4next}${input}"
        save4next=""
        orig="${input}"
        matches=0
        while ((${#input})) ; do
                if [[ $input = *(?)${pattern}*(?) ]] ; then
                        ((matches=matches+1))
                        leftover=${input#*${pattern}}
                        temp=${input%${leftover}}
                        lead=${temp%${pattern}}
                        this=${temp#${lead}}
                        input="${leftover}"
                        ((pos=pos+${#lead}))
                        echo $preamble $pos MATCH: $this
                        ((pos=pos+${#this}))
                else
                        ((pos=pos+${#input}))
                        if (( ${#input} < 5 )) ; then
                                save4next="${input}"
                        else
                                temp="${input%?????}"
                                save4next="${input#$temp}"
                        fi
                        ((pos=pos-${#save4next}))
                        input=""
                fi
        done
done
exit 0

Line: 20 At position 953 MATCH: rrrgds
Line: 26 At position 1248 MATCH: rgrfvt
Line: 49 At position 2440 MATCH: rhrars