Find GNU coreutils executable (portable)

check-coreutils.sh

#!/bin/sh

is_gnu() {
	command -v "$1" >/dev/null \
		&& "$1" --help 2>&1 | grep "@gnu.org" >/dev/null
}

get_gnu() {
	if is_gnu "$1"; then
    # is regular name
		echo "$1"
	elif is_gnu "g$1"; then
    # is g<name> (homebrew coreutils)
		echo "g$1"
	else
    # not found
		echo "Error: no gnu coreutils utility found for '$1'" >&2
		exit 1
	fi
}

# either verify yourself...
grep="$(get_gnu "grep")"
if [ ! "$grep" ]; then exit 1; fi
echo "hello world" | "$grep" -P "^hello"

# ...or set -e (exit immediately if a command exits with a non-zero status)
set -e
grep="$(get_gnu "grep")"
echo "hello world" | "$grep" -P "^hello"