compress a file/directory using the best available algorithm/application (add/delete as applicable)

compress.sh

#!/bin/sh

FORMATS="xz lzip lzma bzip2 gzip lzop 7z rar zip"
LEVELS=$(seq 1 9)

if test -z "$1"
then
	echo "Usage: $(basename $0) <file/dir to compress> [format]"
	echo "Supported formats: $FORMATS"
	exit 1
fi

function format_to_ext()
{
	frmt=$1
	case $frmt in
		"bzip2") echo "bz2"   ;;
		"gzip")  echo "gz"    ;;
		"lzop")  echo "lzo"   ;;
		"lzip")  echo "lz"    ;;
		*)       echo "$frmt" ;;
	esac
}

function compress_file()
{
	file=$1
	xtra=$2
	frmt=$3
	levl=$4
	extn=$(format_to_ext $frmt)
	arch=$ctmp$xtra-$levl.$extn
	test $frmt = "rar" -a $levl -gt 5 && return
	case $frmt in
		"7z")  $frmt a -mx=$levl $arch $xtra >/dev/null 2>&1 ;;
		"rar") $frmt a -m$levl -idq $arch $xtra    ;;
		"zip") $frmt -r -$levl --quiet $arch $xtra ;;
		*)
			arch=$ctmp$file-$levl.$extn
			$frmt --stdout -$levl $file > $arch
			;;
	esac
	echo "$(stat $arch | grep Size | awk '{print $2}') $frmt $levl $arch"
}

function remove_larger()
{
	best=$1
	file=$(echo $2 | cut -d" " -f4)
	test $best != $file && unlink $file
}

function file_size()
{
	file=$1
	echo $(stat $file | grep Size | awk '{print $2}')
}


function compress_file_loop()
{
	ctmp="$(mktemp --directory)/"
	file=$1
	xtra=$2
	frmt=$3
	test -z "$frmt" && frmt=$FORMATS
	cpus=$(nproc)

	export ctmp
	export -f format_to_ext
	export -f compress_file
	export -f remove_larger
	list=$(parallel --bar --jobs $cpus compress_file $file $xtra {} {} ::: $frmt ::: $LEVELS)

	best=$(echo "$(echo "$list")" | sort | head -n1)
	size=$(echo $best | cut -d" " -f1)
	frmt=$(echo $best | cut -d" " -f2)
	levl=$(echo $best | cut -d" " -f3)
	name=$(echo $best | cut -d" " -f4)
	extn=$(format_to_ext $frmt)

	if test $(file_size $name) -gt $(file_size $file)
	then
		echo "Best left uncompressed"
		name="x"
	fi

	parallel --jobs $cpus remove_larger $name {} ::: "$list"

	arch=$file
	case $frmt in
		"7z")  arch=$xtra ;;
		"rar") arch=$xtra ;;
		"zip") arch=$xtra ;;
		*) ;;
	esac
	test $name != "x" && mv $name $arch.$extn
	rmdir $ctmp
}

function compress_directory()
{
	dir=$1
	fmt=$2
	tar --create --file $dir.tar $dir
	compress_file_loop $dir.tar $dir $fmt
	unlink $dir.tar
}


if test -n "$2"
then
	found=0
	for f in $FORMATS
	do
		test $f = $2 && found=1
	done
	if test $found -eq 0
	then
		echo "Unsupported archive format"
		exit 1
	fi
fi

if test -d $1
then
	compress_directory $1 $2
elif test -f $1
then
	compress_file_loop $1 $1 $2
else
	echo "Unsupported file type"
	exit 1
fi

exit 0