Choose among multiple similar commands in bash script

command_choices.sh

#!/bin/bash

# If the functionality of a GNU command (vs BSD) is needed, instead of checking for $OSTYPE, check if command is installed.
# This method isn't perfect, because you could have the case where the preferred command isn't installed when you expect it to be
# (e.g. Mac has no gdate installed). Perhaps in combination with $OSTYPE for better coverage.

# This checks if gdate is installed (likely beacuse running in a Mac environment). If not, use the normal date command.
DATE=$(type -p gdate date | head -n 1)

# Execute the command
$DATE +%Y%m%d