How to loop over a directory of files in Linux and perform a command on each file in turn. Examples below are using Ubuntu 12.04.

A quick one-liner for the impatient that will print out all .JPG files in the current directory

for f in *.jpg; do echo $f; done

It’s easier to read and understand when written out over multiple lines

for f in *.jpg
do
  echo $f
done

Inside the loop $f is the name of the file, you could change your loop to use ImageMagick to convert the JPEG from using CMYK to RGB colorspace

for f in *.jpg
do
  convert $f -colorspace RGB $f
done