#!/bin/bash
# mssrnm: simple script to mass rename files.
# This script is quite trivial, so there's no need to cover it with a license.
# Just use the code as you see fit.

if [[ $1 == "-h" || $1 == "--help" ]]; then
    echo "    This script mass renames files."
    echo "
    First parameter is the number of ciphers to be used.
    Specifying \"5\" will rename the files in the following order:
      some_pic\$ssuffix => 00000\$esuffix
      anotheri\$ssuffix => 00001\$esuffix
      vacation\$ssuffix => 00002\$esuffix
      speakers\$ssuffix => 00003\$esuffix
      ...
      blahblah\$ssuffix => 04798\$esuffix
    etc.
    The default is \"3\".
    \$ssuffix is determined by the second parameter. The default is \".JPG\".
    \$esuffix is determined by the third parameter. The default is \".jpg\".

    Example:
      $ mssrnm 4 .JPG .jpg
    This will rename all *.JPG files into 0000.jpg, 0001.jpg, 0002.jpg, etc.
"
exit
elif [ ! $1 ]; then
    glen=3
else
    glen="$1"
fi

if [ ! $2 ]; then
    ssuffix=".JPG"
else
    ssuffix="$2"
fi

if [ ! $3 ]; then
    esuffix=".jpg"
else
    esuffix="$3"
fi

i="0"
for file in *"$ssuffix"; do
    len=${#i}
    rlen=`expr $glen - $len`
    name=$i
    for ((ii=0;ii<$rlen;ii+=1)); do
        name=0"$name"
    done
    name="$name$esuffix"
    echo "$file => $name"
    mv "$file" "$name"
    i=`expr $i + 1`
done