Punt is_function in favour of POSIX shell builtin command, thanks to Harald van Dijk for the idea.

sh/runscript.sh.in

@@ -94,7 +94,7 @@ unset _f
 
 # If we have a default command then supply a default start function
 if [ -n "${command}" ]; then
-	if ! is_function start; then
+	if ! [ "$(command -v start)" != "start" ]; then
 		start() {
 			local _background=
 			ebegin "Starting ${name:-${RC_SVCNAME}}"
@@ -126,7 +126,7 @@ fi
 # If we have a default command, procname or pidfile then supply a default stop 
 # function
 if [ -n "${command}" -o -n "${procname}" -o -n "${pidfile}" ]; then
-	if ! is_function stop; then
+	if ! [ "$(command -v stop)" != "stop" ]; then
 		stop() {
 			ebegin "Stopping ${name:-${RC_SVCNAME}}"
 			start-stop-daemon --stop \
@@ -143,7 +143,7 @@ while [ -n "$1" ]; do
 	for _cmd in describe start stop ${extra_commands:-${opts}} \
 		${extra_started_commands}; do
 		if [ "${_cmd}" = "$1" ]; then
-			if is_function "$1"; then
+			if [ "$(command -v "$1")" = "$1" ]; then
 				# If we're in the background, we may wish to
 				# fake some commands. We do this so we can
 				# "start" ourselves from inactive which then
@@ -168,11 +168,11 @@ while [ -n "$1" ]; do
 					fi
 				done
 				unset _cmd
-				if is_function "$1"_pre >/dev/null 2>&1; then
+				if [ "$(command -v "$1_pre")" = "$1_pre" ]; then
 					"$1"_pre || exit $?
 				fi
 				"$1" || exit $?
-				if is_function "$1"_post >/dev/null 2>&1; then
+				if [ "$(command -v "$1_post")" = "$1_post" ]; then
 					"$1"_post || exit $?
 				fi
 				shift