filenuminc.sh

#!/bin/bash
#
## @file filenuminc.sh
## @brief Convenience script to rename files beginning with a track number
## @author Ronald Joe Record (rr at ronrecord dot com)
## @copyright Copyright (c) 2014, Ronald Joe Record, all rights reserved.
## @version 1.0.1
##
## The filenuminc script renames files beginning with a track number
## after increasing the number by some previously ripped number of tracks.
## For example, the command "filenuminc 11" would rename "04 My Song.mp3"
## to "15 My Song.mp3".

## @fn usage()
## @brief Display command line usage options
## @param none
##
## Exit the program after displaying the usage message and example invocations
usage() {
    echo "Usage: filenuminc <number>"
    echo "Where <number> is a two digit number between 01 and 99"
    exit 1
}

## @fn is_all_digits()
## @brief Returns false if any of the characters in the argument is not a digit
## @param param1 string to check for digits
is_all_digits() {
    case $1 in *[!0-9]*) false;; esac
}

[ "$1" ] || usage

INC=$1

is_all_digits $INC || usage

for i in *.mp3
do
    [ "$i" = "*.mp3" ] && continue
    num="${i:0:2}"
    newnum=`expr $num + $INC`
    j=`echo $i | sed -e "s/$num/$newnum/"`
    [ "$i" = "$j" ] || mv "$i" "$j"
done