lsump

# lsump
#
# read (and parse) the ls -l output
#
# -rwxr-xr-x  1 chetharrison  staff    895 Oct 14 08:47 arg
# -rwxr-xr-x  1 chetharrison  staff    203 Oct  9 10:12 fc
#
# options:
# -a - print an average file size
# -c - print a file count
# -t - print a total file size
# -u user - only count files for this user

while getopts "actu:" FLAG  # define flags in alphabetical order by convention. Note the `u:` option means it takes an arg.
do
	case $FLAG in
	a) AFLAG=set  # set is an arbitrary value that simple means the AFLAG is not null.
		;;
	c) CFLAG=set
		;;
	t) TFLAG=set
		;;
	u) UVAL="$OPTARG"  # UFLAG is set to the associated argument value here
		;;
	*) echo "usage: ${0##*/} [-a] [-c] [-t] [-u username]"
	   echo "example: ${0##} -ac -u user"
	   exit 1
	   	;;
	esac
done >&2  # sending stderr to stdout is good practice

declare -i COUNT=0

ls -l | { while read PERM LN USR GRP SIZ MON DAY YRTM FILENM  # start of subshell block
do
	if [[ ! $FILENM ]] ; then continue ; fi
	if [[ ! "$UVAL" && "$USR" != "$UVAL" ]] ; then continue ; fi
	COUNT+=1
	[[ $VFLAG ]] && echo "File: '$FILENM' IS $SIZ bytes long."
	(( TOTAL += SIZ ))
done
[[ $CFLAG ]] && echo $COUNT files.  # this is an if statment hack
[[ $TFLAG && $TOTAL ]] && echo $TOTAL bytes total.
if [[ $AFLAG && (( COUNT > 0 )) ]]
then
	let "AVG=($TOTAL+($COUNT/2))/$COUNT"
	printf "%d bytes per file on average\n" $AVG
fi
} # end of sub shell block