Original file script.sh:
#!/usr/bin/env bash
echo "foo"
Create other.sh
$ echo '#!/usr/bin/env bash' > other.sh
$ echo "echo '$(base64 script.sh)' | base64 -d | sh" >> other.sh
$ chmod +x other.sh
Result (cat other.sh):
#!/usr/bin/env bash
echo 'IyEvdXNyL2Jpbi9lbnYgYmFzaAplY2hvICJmb28iCg==' | base64 -d | sh
Try:
$ ./other.sh
foo