extsort.bash

#!/bin/bash

# extsort.bash

# do some operations with lists in bash such as lists of file extensions or
# required binaries. demo for loop and regexp techniques


# extension lists
VIDEXTS="mkv mp4 avi flv webm wmv mpg ogv VOB wmv ts"
AUDEXTS="flac mp3 pcm mp2 mpa mpc ogg oga ape  m4a aac aiff au wma wav wv"
IMGEXTS="gif png jpg tiff xpm pcx svg"
DOCEXTS="doc txt ps pdf dvi asc conf html"

# requirement binaries list (example)
REQUIRES="bash du date tput diff ls" # these should be standard and present
#REQUIRES="joe dos2unix clickedit nopass" # these might fail (testing)

########################################################################
# FOR LOOP TECHNIQUE
# a function to see if we have all the binaries

check_requirements()
{
    local OUT=      # uninitialized
    L=("${1}")      # a local copy of a list turned into an array

    for R in ${L[@]}    # iterate through array
    do
    P=$(which "${R}")  #check for each binary in PATH

    if [[ ! "${P}" ]] ; then    # OOPS we are missing one
        OUT="${R}"              # which one
        break                   # bail
    fi
    done

    if [[ ! ${OUT} ]]; then   # nothing missing?
    echo "ALL"            # good
    else
    echo "${OUT}"         # bad. echo which binary was not found
    fi
} #check_req


REQS=$(check_requirements "${REQUIRES}")

if [ "X${REQS}" != "XALL" ] ; then
    (>&2 echo "${REQS} was not found in the the following paths:")
    (>&2 echo "${PATH}")
    exit 1
fi

#################################################################
# REGEXP TECHNIQUE
# operate on files we are interested in

let vcounter=0  # some integers for counting
let acounter=0
let icounter=0
let counter=0
let n=0

declare -a FileList  # define some string arrays
declare -a vext
declare -a aext
declare -a iext

declare -a vfiles
declare -a afiles
declare -a ifiles

FileList=( "$@" )      # make an array from the lists for iteration
vext=("${VIDEXTS}")
aext=("${AUDEXTS}")
iext=("${IMGEXTS}")

n=${#FileList[@]}           # number of elements in array

while (( counter < n ))     # arithmetic evaluation
do
    F=${FileList[counter]}  # array indexing

    ext="${F##*.}"          # regexp ( VAR##*. =  "everything after the last '.' ")

    # video or audio or image file?
    if [[ "${VIDEXTS}" =~ "${ext}" ]] ; then # (" does ext exist in VIDEXTS?" )
    vfiles+=( ${F} )
        vcounter=$((vcounter + 1))
    fi

    if [[ "${AUDEXTS}" =~ "${ext}" ]] ; then # (" does ext exist in AUDEXTS?" )
    afiles+=( ${F} )
        acounter=$((acounter + 1))
    fi


    if [[ "${IMGEXTS}" =~ "${ext}" ]] ; then # (" does ext exist in IMGEXTS?" )
    ifiles+=( ${F} )
        icounter=$((icounter + 1))
    fi

    counter=$((counter + 1))

done


# so we emerge with
#    video files sorted into vfiles array
echo "${vcounter} video files:  ${vfiles[@]}"

#    audio files sorted into afiles array
echo "${acounter} audio files:  ${afiles[@]}"

#    image files sorted into ifiles array
echo "${icounter} image files:  ${ifiles[@]}"

#END