shellTube/gendl

#!/bin/sh
##############################
# name: gendl
# lisc: gnu gplv3
# desc: download to stdout or
#       file, independent of
#       a specific downloader.
#       ftp/wget/curl support.
# main: jadedctrl
##############################

# usage: gendl [-o output] url



#---------------------------------------
# backend bits

# NIL --> STRING
# return the download program you're using
function download_program
{
	programs="ftp curl wget"
	current=""

	for program in $programs
	do
		if whereis $program > /dev/null
		then
			current=$program
		fi
	done

	if uname -s | grep -e "LibertyBSD" -e "OpenBSD" > /dev/null
	then
		current="ftp"
	fi

	echo "$current"
}

# STRING PATH --> NIL
# download URL $1 to stdout
function download_stdout
{
	program=$(download_program)
	url=$1

	case "$program" in
		"ftp")
			output="$(ftp -VMo- $url)"
			;;
		"curl")
			output="$(curl $url)"
			;;
		"wget")
			output="$(wget --quiet -O $url)"
			;;
	esac

	return_code=$?

	echo "$output"
	return $return_code
}

# STRING PATH --> NIL
# download URL $1 to path $2
function download_file
{
	program=$(download_program)
	url=$1
	path=$2

	case "$program" in
		"ftp")
			ftp -VMU "." -o $path $url
			;;
		"curl")
			curl -o $path $url
			;;
		"wget")
			wget --quiet -O $path $url
			;;
	esac

	return_code=$?

	if test $return_code -ne 0
	then
		rm $path 2> /dev/null
		# for consistency in behavior; wget saves 404s anyway, whereas
		# ftp doesn't save anything from 404s, etc.
	fi

	return $return_code
}



# --------------------------------------
# front-end string-manip

# STRING --> STRING
# return the last word in a string
function last_word
{
	string="$1"

	echo "$string" \
	| rev \
	| sed 's% .*%%' \
	| rev
}

function usage
{
	echo "usage: gendl [-o output] URL"
}



# --------------------------------------
# invocation

args="$(getopt o: $*)"
if test $? -ne 0 || test -z "$@"
then
	usage
	exit 2
fi


set -- $args
while test $# -ne 0
do
	case "$1"
	in
		-o)
			download_path="$2"; shift; shift;;
		--)
			shift; break;;
	esac
done


url="$(last_word "$@")"


if test -n "$download_path"
then
	download_file $url $download_path
else
	download_stdout "$url"
fi