Create 1x versions of all images in the CWD.

unretinify.sh

#!/bin/sh

#
# Create 1x versions of all images in the CWD.
#

IFS=$'\n'
for file in `ls *@2x*`
do
  new_file=`echo $file|sed 's/@2x//g'`

  size=`identify "$file" 2>/dev/null|cut -d ' ' -f3`
  width=`echo $size|cut -dx -f-1`
  new_width=`expr $width / 2`
  height=`echo $size|cut -dx -f2-`
  new_height=`expr $height / 2`
  
  convert "$file" -resize ${new_width}x$new_height "$new_file" 2>/dev/null
done

Shell programming, how does it even work?