!convert
 convert -geometry 100 foo.jpg foo2.jpg # (width)
 convert -geometry x100 foo.jpg foo2.jpg # (height)
 $ for i in *.JPG; do convert -geometry 100 $i t/$i; done

!EXIF (identify)
http://www.imagemagick.org/script/command-line-options.php#format

 identify -format "%[EXIF:*]" foo.jpg
 identify -format "%[EXIF:DateTimeOriginal]" foo.jpg