is_sourced.sh

#!/bin/bash
script_name=$( basename ${0#-} ) #- needed if sourced no path
this_script=$( basename ${BASH_SOURCE} )
if [[ ${script_name} = ${this_script} ]] ; then
    echo "running me directly"
else
    echo "sourced from ${script_name}"
fi 
echo '----------'
if [ "$(basename $0)" = "$(basename $BASH_SOURCE)" ]; then
    echo "running directly"
else
    echo "sourced from $0"
fi
echo '----------'
if [ ${#BASH_SOURCE[@]} -eq 1 ]; then echo "running directly"; else echo "sourced from $0"; fi

echo '----------'

# USE THIS ONE!
# check to see if this file is being run or sourced from another script
function _is_sourced() {
    # See also https://unix.stackexchange.com/a/215279
    # macos bash source check OR { linux shell check }
    [[ "${#BASH_SOURCE[@]}" -eq 0 ]] || { [ "${#FUNCNAME[@]}" -ge 2 ]  && [ "${FUNCNAME[0]}" = '_is_sourced' ] && [ "${FUNCNAME[1]}" = 'source' ]; }
}
if ! _is_sourced; then echo "direct"; else echo "sourced $0"; fi