Rename Filename Loop Bash

gistfile1.sh

#!/bin/bash

# Rename files in dir to slide_##.pdf with two numerals
# Exampe filename: UMB_AR App_AN_041515_FA.33.pdf

foo = 0

for f in *.pdf
do

  NEW_NAME="$(echo "$f" | sed 's/\UMB_AR App_AN_041515_FA.//g')"

  #Find names with 1 char number
  if [ ${#NEW_NAME} -eq 5 ];
  then
    zero=0
    foo=$zero$NEW_NAME
  else
    foo=$NEW_NAME
  fi

  STR1=slide_
  FINAL=$STR1$foo
  echo $FINAL

  mv "$f" "$FINAL"

done

gistfile2.sh

#!/bin/bash
# Rename files in dir
# Filename example slide_slide_30.pdf
# Need to remove the first slide_

for f in *.pdf
do

  echo $f | sed 's/^slide_//'
  foo="$(echo "$f" | sed 's/^slide_//')"
  echo $foo
  mv "$f" "$foo"
done

gistfile3.sh

#!/bin/bash
# Rename files in dir by subtracting their numerical names
#ie 01.pdf will become 0.pdf, 02.pdf will become 1.pdf

one=1

for f in *.pdf
do

 file=$(basename "$f")
 extension=${f##*.}
 number=${file%.*}
 #echo $number

 num=`expr $number - $one`
 name=$num.pdf

 echo $name
 mv "$f" "$name"
 
done