How to auto-rotate digital photos to their proper orientation/exifautotran code

This code is from Gentoo Linux's patch to jpeg lib, an improved version of http://sylvana.net/jpegcrop/exifautotran.txt

#!/bin/sh
# exifautotran [list of files]
#
# Transforms JPEG files so that Exif Orientation becomes 1
#
for i
do
  case $i in
    -v|--version) echo "exifautotran"; exit 0;;
    -h|--help) 
      cat <<EOF
exifautotran [list of files]

Transforms JPEG files so that Exif Orientation becomes 1
EOF
    exit 0;;
  esac

  case `jpegexiforient -n "$i"` in
    1) transform="";;
    2) transform="-flip horizontal";;
    3) transform="-rotate 180";;
    4) transform="-flip vertical";;
    5) transform="-transpose";;
    6) transform="-rotate 90";;
    7) transform="-transverse";;
    8) transform="-rotate 270";;
    *) transform="";;
  esac

  if test -n "$transform"; then
    echo Executing: jpegtran -copy all $transform $i >&2
    jpegtran -copy all $transform "$i" > tempfile
    if test $? -ne 0; then
      echo Error while transforming $i - skipped. >&2
    else
      rm "$i"
      mv tempfile "$i"
      jpegexiforient -1 "$i" > /dev/null
    fi
  fi
done