gistfile1.txt

#~/bin/bash
shopt -s extglob

# usage ./.partition <$1 path to directory taht contains image files to be converted to pdf> <$2 number of images converted in a lap> <$3 scale "x y" optional> >
# ./.partition path/to/directory 10 "0.9 0.9"

# dependencies: pdftk and cpdf 


cd "$1"
i=0
ff=""
# natural order
for fn in $(ls -vw0 *.jpg); do
    # comcatenate filenames
    ff="${ff} ${fn}"
    # increment
    let i=$i+1
    if ((i % $2 ==  0)); then
        echo "convert $ff $i.pdf"
        convert $ff $i.pdf
        # reset concatenated
        ff=""
    fi
done
# exiting from for cycle left some work to be done
if [ ! -z "${ff}" ]; then
    echo "convert $ff $i.pdf"
    convert $ff $i.pdf
fi

chars=abcd1234ABCD
rnd=""
for i in {1..8} ; do
    rnd="${rnd}${chars:RANDOM%${#chars}:1}"
done
random_name="${rnd}.pdf"
# concatenate
pdftk $(ls -vw0 *.pdf) cat output $random_name

# remove all individual pdf if concatenation succeeded
status=$?
if [ $status -eq 0 ]; then
    echo "removing individual pdf file"
    rm !("$rnd").pdf
fi

# scale if requested
status=$?
if [[ $status -eq 0 && ! -z $3 ]]; then
    echo "scaling pdf file"
    cpdf -scale-page="$3" "$random_name" -o "${random_name}.scale"
    mv "${random_name}.scale" "$random_name"  
fi