#!/bin/bash
pname="`basename $0`"
pblan="`echo $pname|sed -e 's/./ /g'`"
prob=1
TOP=1000000

function usage {
    echo "$pname usage:"
    echo ""
    echo "    $pname [--help|--probability=F|--one-file] [--] file..."
    echo ""
    echo "F begin a number between 0.0 and 1.0,"
    echo ""
    echo "With --one-file, prints one of the files, selected with "
    echo "equiprobability. Tgis is the default."
    echo ""
    echo "With --probability=F, prints a selection of files, each file having "
    echo "probability F of being selected (which means that a mean "
    echo "of F*{nb of files} files are printed).  Only one --probability is "
    echo "taken into account (the last)."
    echo ""
}

allfile=0
onefile=1
nfile=0

for arg ; do
    case "$arg" in
    --help|-h)
        usage
        exit 0
        ;;
    --one-file)
        onefile=1
        ;;
    --probability=[01].[0-9]*)
        onefile=0
        number="`echo $arg|sed -e 's/--probability=//'`"
        prob=`echo $number $TOP \* p | dc | sed -e 's/\..*//'`
        if [ $TOP -le $prob ] ; then
            echo "${pname}: number too big: $number"
            usage
            echo 2        
        fi
        ;;
    --probability=*)
        number="`echo $arg|sed -e 's/--probability=//'`"
        echo "${pname}: invalid number: $number"
        usage
        echo 2        
        ;;
    --)
        allfiles=1
        ;;
    -*)
        if [ $allfiles -ne 0 ] ; then
            files[$nfile]="$arg"
            nfile=$(( $nfile + 1 ))
        else
            echo "${pname}: invalid option: $arg"
            usage
            echo 1
        fi
        ;;
    *)
        files[$nfile]="$arg"
        nfile=$(( $nfile + 1 ))
        ;;
    esac
done

# echo ${nfile}
# echo ${files[@]}
if [ $onefile -ne 0 ] ; then
    echo ${files[$(( 1 + $( ~/bin/random  ${#files[@]} ) ))]}
else
    for arg in "${files[@]}" ; do
        if [ `random $TOP` -le $prob ] ; then
            echo $arg
        fi
    done
fi

exit 0