Don't assume that file binary exists on *nix OS

teohhanhui · teohhanhui · commit ad148d7b9a0e · 2018-04-12T16:37:59.000+02:00
Certain lightweight distributions such as Alpine Linux (popular for smaller Docker images) do not include it by default.
diff --git a/src/Symfony/Component/HttpFoundation/File/MimeType/FileBinaryMimeTypeGuesser.php b/src/Symfony/Component/HttpFoundation/File/MimeType/FileBinaryMimeTypeGuesser.php
@@ -43,7 +43,7 @@ public function __construct($cmd = 'file -b --mime %s 2>/dev/null')
      */
     public static function isSupported()
     {
-        return '\\' !== DIRECTORY_SEPARATOR && function_exists('passthru') && function_exists('escapeshellarg');
+        return '\\' !== DIRECTORY_SEPARATOR && function_exists('passthru') && function_exists('escapeshellarg') && self::hasFileBinary();
     }
 
     /**
@@ -82,4 +82,34 @@ public function guess($path)
 
         return $match[1];
     }
+
+    /**
+     * @return bool
+     */
+    private static function hasFileBinary()
+    {
+        static $exists;
+
+        if (isset($exists)) {
+            return $exists;
+        }
+
+        ob_start();
+
+        passthru('command -v file', $return);
+        if ($return > 0) {
+            ob_end_clean();
+
+            return $exists = false;
+        }
+
+        $binPath = trim(ob_get_clean());
+
+        if (!preg_match('#^(?:/[^\0/])+#', $binPath)) {
+            // it's not a bin path, but an error message
+            return $exists = false;
+        }
+
+        return $exists = true;
+    }
 }
