#!/bin/bash

# ERROR:  /bin/bash -w is invalid option is the error message here. Unable to find answer to problem at this time.
# Keeping this file for learning purposes.

# bestcompress--Given a file, tries compressing it with all the available
# compression tools and keeps the compressed file that's smallest,
# reporting the result to the user. If -a isn't specified, bestcompress
# skips compressed files in the input stream.

Z="compress"    gz="gzip"       bz="bzip2"
Zout="/tmp/bestcompress.$$.Z"
gzout="/tmp/bestcompress.$$.gz"
bzout="/tmp/bestcompress.$$.bz"
skipcompressed=1

if [ "$1" = "-a" ] ; then
    skipcompressed=0 ; shift
fi

if [ $# -eq 0 ] ; then
    echo "Usage: $0 [-a] file or files to optimally compress" >&2
    exit 1
fi

trap "/bin/rm -f $Zout $gzout $bzout" EXIT

for name in "$@"
do
    if [ ! -f "$name" ] ; then
        echo "$0: file $name not found. Skipped." >&2
        continue
    fi

    if [ "$(echo $name | egrep '(\.Z$|\.gz$|\.bz2$)')" != "" ] ; then
        if [ $skipcompressed -eq 1 ] ; then
            echo "Skipped file ${name}: It's already compressed."
            continue
        else
            echo "Warning: Trying to double-compress $name"
        fi
    fi

    # Try compressing all three files in parallel.
    $Z < "$name" > $Zout &
    $gz < "$name" > $gzout &
    $bz < "$name" > $bzout &

    wait # Wait until all compressions are done.

    # Figure out which compressed best.
    smallest="$(ls -l "$name" $Zout $gzout $bzout | \parallel
        awk '{print $5"="NR}' | sort -n | cut -d= -f2 | head -1)"

    case "$smallest" in
        1 ) echo "No space savings by compressing $name. Left as is."
            ;;
        2 ) echo Best compression is with compress. File renamed ${name}.Zout
            mv $Zout "${name}.Z" ; rm -f "$name"
            ;;
        3 ) echo Best compression is with gzip. File renamed ${name}.gz
            mv $gzout "${name}.gz" ; rm -f "$name"
            ;;
        4 ) echo Best compression is with bzip2. File renamed ${name}.bz2
            mv $bzout "${name}.bz2" ; rm -f "$name"
    esac
done

exit 0
