su-with-args

#!/bin/sh -e
# SPDX-License-Identifier: WTFPL

usage () {
	cat <<- EOF
		usage: $0 USER COMMAND [ARGS…]

		Calls \`su\` to run COMMAND ARGS… under USER.
		Handles commands and args with spaces.
		Example: su-with-args root cat /etc/passwd

		Why isn't \`su -c "COMMAND ARGS"\` enough?
		Because of spaces and to pass extra args, e.g. with \`rsync --rsh\`.

		Note: passes --pty and --login options to \`su\`.
		Note: uses COMMAND as command name (like \$0 but purely informational).
	EOF
}

if [ $# -lt 2 ]
then
	usage >&2
	exit 64  # EX_USAGE
fi

user=$1
shift

exec su --pty - "$user" -- -c '"$@"' "$1" "$@"