#!/bin/bash

###
#
# Run this from within the target directory. For ease of use, you
# may want to put this in ~/bin/ if that is in your $PATH variable.
#
# Start numbering at 1
# ./even-odd-pages.sh *
#
# Start numbering at 2
# ./even-odd-pages.sh 2 *
#
###


# If the first parameter is a number use that as starting position
if [[ $1 =~ ^[0-9]*$ ]]; then START=$1; shift; else START=1; fi

# If file input is not given quit, else continue
if [[ ! $1 ]]; then
  echo -e "\nFile input is required\n"; exit;

else

# Initialize counter to the start value
i=$START

# Loop through as sorted list of input files and rename them
for x in $@; do echo $x; done | sort -n\
 | while read FILENAME; do

  # Assuming .jpg since this is for images/pages.
  mv -v $FILENAME ${i}.jpg;

  # Increment counter
  ((i+=2))

done

fi