mktemp implemented in .sh, understands 2 parameters tmpdir and suffix

gistfile1.txt

#!/bin/sh

tmpdir=/tmp
unset suffix

while [ -n "$1" ]; do
 case $1 in
  --tmpdir=*)
   tmpdir=${1#*=}
   ;;
  --suffix=*)
   suffix=${1#*=}
   ;;
  *)
   echo 'bad parameter' 1>&2
   exit 1
 esac
 shift
done

while [ 1 ] ; do
 f=$tmpdir/"$$"-${RANDOM}$suffix
 [ -f $f ] && continue
 >$f ||
  (
   echo "failed to create file %f" 1>&2
   exit 1
  )
 echo $f
 exit 0
done