cd /tmp
cat > foo.sh <<EOT
#!/bin/sh
echo Relative path
./bar.sh
echo Absolute path
/tmp/bar.sh
echo No path
bar.sh
EOT
cat > bar.sh <<EOT
#!/bin/sh
echo bar running as \$0
EOT
chmod 0755 foo.sh bar.sh
sudo chown root bar.sh
sudo cp -p bar.sh /usr/local/bin
./foo.sh