awk '
BEGIN {
pos='$1'
lon='$2'
ref='$3'+0
}
{
n=substr($0,pos,lon)+0
if ( n == ref )
   {
    printf "\t%s\n", $0
    net++
   }
}
END {
printf "\n\t Etoiles selectionnees: %3d\n\n", net
} '