Rename all file in the current directory according to their file creation date For jpegs the file date will be set according to its EXIF data e.g. "20130628_014218.txt" not renamed "test.TXT" => "20130628_002938.txt" file extensions will be lower case

rename_to_date.sh

#!/usr/bin/env sh

# Rename all file in the current directory according to their file creation date
# For jpegs the file date will be set according to its EXIF data
# e.g. 
#     "20130628_014218.txt" not renamed
#     "test.TXT" => "20130628_002938.txt"
# file extensions will be lower case

jhead -ft -dt -autorot -exonly -n%Y%m%d_%H%M%S *.[Jj][Pp][Gg]

find . -maxdepth 1 -type f -printf '%f\t%TY%Tm%Td_%TH%TM%TS\n' | awk '
  BEGIN { _ord_init(); suf = "" }
  function _ord_init(    low, high, i, t) {
    low = sprintf("%c", 7)
    if (low == "\a") {
      low = 0
      high = 127
    } else if (sprintf("%c", 128 + 7) == "\a") {
      low = 128
      high = 255
    } else {
      low = 0
      high = 255
    }
    
    for (i = low; i <= high; i++) {
      t = sprintf("%c", i)
      _ord_[t] = i
    }
  }
  function ord(str, c) {
    c = substr(str, 1, 1)
    return _ord_[c]
  }
  function chr(c) {
    return sprintf("%c", c + 0)
  }
 {
  a=$0;
  split(a, arr, "\t")
  old_name = arr[1]

  ext = arr[1]
  gsub(/^.*\./, "", ext)

  sub(/\..*$/, "", arr[2])
  new_name = arr[2]

  if (old_name == new_name"."tolower(ext)) {
    print "\""arr[1]"\" not renamed"
  } else {
    #print system("ls "old_name)
    suf = ""
    while (system("ls "sprintf("%s%s%s", new_name, suf,"."tolower(ext))" > /dev/null 2>&1") == 0) {
       print sprintf("%s%s%s", new_name, suf,"."tolower(ext))" already exists"
       last = substr(suf, length(suf), length(suf)+1)
       if (last == "") {
         suf = "a"
       } else {
         if(last == "z") {
           suf = suf"a"
         } else {
           suf = substr(suf, 1, length(suf)-1)chr(ord(last) + 1)
         }
       }
    }
    new_name = sprintf("%s%s%s", new_name, suf,"."tolower(ext))
    
    print "\""arr[1]"\" => \""new_name"\""
    system("mv \""arr[1]"\" "new_name)
  }
}'

Mac:

brew install jhead
brew install findutils --with-default-names