diff --git a/src/_h5ai/client/js/scripts.js b/src/_h5ai/client/js/scripts.js
index 494679e4..2cd41816 100644
--- a/src/_h5ai/client/js/scripts.js
+++ b/src/_h5ai/client/js/scripts.js
@@ -30,6 +30,7 @@
 
 	var	$ = jQuery,
 		module = $('script[data-module]').data('module'),
+		data = {action: 'get', setup: true, options: true, types: true, theme: true, langs: true},
 		url;
 
 	if ($('html').hasClass('no-browser')) {
@@ -39,6 +40,7 @@
 	if (module === 'main') {
 		url = '.';
 	} else if (module === 'info') {
+		data.updatecmds = true;
 		url = 'server/php/index.php';
 	} else {
 		return;
@@ -46,7 +48,7 @@
 
 	$.ajax({
 		url: url,
-		data: {action: 'get', setup: true, options: true, types: true, theme: true, langs: true},
+		data: data,
 		type: 'POST',
 		dataType: 'json'
 	}).done(function (config) {
diff --git a/src/_h5ai/server/php/inc/setup.php b/src/_h5ai/server/php/inc/setup.php
index 3d22abc8..4056f281 100644
--- a/src/_h5ai/server/php/inc/setup.php
+++ b/src/_h5ai/server/php/inc/setup.php
@@ -81,18 +81,29 @@ function setup() {
 	define("CACHE_HREF", normalize_path(APP_HREF . "/cache", true));
 	define("CACHE_PATH", normalize_path(APP_PATH . "/cache", false));
 	define("HAS_WRITABLE_CACHE", @is_writable(CACHE_PATH));
+	define("CMDS_PATH", normalize_path(CACHE_PATH . "/cmds.json", false));
 
 
 	// EXTERNAL COMMANDS
-	// todo: cache all cmd tests
-	$cmd = false;
-	if (!$cmd && exec_0("command -v command")) {
-		$cmd = "command -v";
+	$cmds = load_commented_json(CMDS_PATH);
+	if (sizeof($cmds) === 0 || has_request_param("updatecmds")) {
+		$cmds["command"] = exec_0("command -v command");
+		$cmds["which"] = exec_0("which which");
+
+		$cmd = false;
+		if ($cmds["command"]) {
+			$cmd = "command -v";
+		} else if ($cmds["which"]) {
+			$cmd = "which";
+		}
+
+		foreach (array("tar", "zip", "convert", "ffmpeg", "avconv", "du") as $c) {
+			$cmds[$c] = ($cmd !== false) && exec_0($cmd . " " . $c);
+		}
+
+		safe_json(CMDS_PATH, $cmds);
 	}
-	if (!$cmd && exec_0("which which")) {
-		$cmd = "which";
-	}
-	foreach (array("tar", "zip", "convert", "ffmpeg", "avconv", "du") as $c) {
-		define("HAS_CMD_" . strtoupper($c), ($cmd !== false) && exec_0($cmd . " " . $c));
+	foreach ($cmds as $c => $has) {
+		define("HAS_CMD_" . strtoupper($c), $has);
 	}
 }
diff --git a/src/_h5ai/server/php/inc/util.php b/src/_h5ai/server/php/inc/util.php
index 4672bea8..338a9332 100644
--- a/src/_h5ai/server/php/inc/util.php
+++ b/src/_h5ai/server/php/inc/util.php
@@ -74,6 +74,13 @@ function load_commented_json($path) {
 }
 
 
+function safe_json($path, $obj) {
+
+	$json = json_encode($obj);
+	return file_put_contents($path, $json) !== false;
+}
+
+
 function passthru_cmd($cmd) {
 
 	$rc = null;