recase - convert input (filename or standard input) to all upper-/lower-case

recase.sh

#!/bin/bash
#
#  Re-case the input to all upper- / lower-case based on the name of the symlink
#  that points to this script
#
#  Author:    Kevin Ernst <ernstki -at- mail.uc.edu>
#  Date:      27 June 2018
#

ME=$(basename "$BASH_SOURCE")
INFILE=

# if a filename argument is given, feed it to tr's stdin
[ -f "$1" ] && INFILE="<'$1'"

case $ME in
    u*)
        # e.g., 'uppercase' or 'ucase'
        # translate lower-case to upper-case
        TRANS="'a-z' 'A-Z'" ;;
    l*|d*)
        # e.g., 'downcase' or 'lowercase'
        # do a lower-case translation instead
        TRANS="'A-Z' 'a-z'" ;;
    *)
        echo >&2
        echo "OH NOES!" >&2
        echo "========" >&2
        echo >&2
        echo "You called this script by a weird name I don't understand!" >&2
        echo >&2
        echo "Try creating a symlink with a name like 'lcase' or 'ucase'." >&2
        echo >&2
        exit 1 ;;
esac

eval "tr $TRANS $INFILE"