Test to share variables within two script.

callee.sh

#!/bin/sh
echo "  #${0} begin"
echo "  echo \$WORKING_DIR"
echo "  ${WORKING_DIR}"
echo "  #${0} end"

caller.sh

#!/bin/sh
echo "#${0} begin"
echo "WORKING_DIR=\$(cd \$(dirname "\${0}"); pwd)"
WORKING_DIR=$(cd $(dirname "${0}"); pwd)
echo "./callee.sh"
./callee.sh  # Run in subshell. The variable not shared.
echo "source callee.sh"
source callee.sh  # The variable shared.
# . callee.sh  # Same as source
echo "#${0} end"