Converts DSC_NNNN.JPG to something like 2008.Jan.01_NNNN.jpg, where the date prefix is derived from the file modification date

dsc_convert.sh

#!/bin/bash

###############################################################################
# Nikon image filename conversion, e.g. (DSC_NNNN.JPG to 2008.Jan.01_NNNN.jpg) 
###############################################################################

# change any spaces to underscores
for i in * ; do
  if [ -f "$i" ] ; then
    echo mv \"$i\" ${i// /_}
  fi
done

# lowercase the extension
for i in `ls -1 *.JPG` ; do echo mv $i ${i%.*}.jpg | sh ; done

# change DSC prefix to date prefix
for i in `ls -1 DSC*` ; do prefix=`ls -lT $i | awk '{print $9"."$6"."$7}'` ; suffix=`echo ${i#*_}` ; echo mv {DSC,$prefix}"_"$suffix | sh ; done