cryptsetup: add a terse help

diff --git a/src/cryptsetup.c b/src/cryptsetup.c
index 506ce9b5c9086bf3d4fec4cd0431affc5bc139ba..989734be1bc44badb3ca130ea14daaece34d1afd 100644 (file)
--- a/src/cryptsetup.c
+++ b/src/cryptsetup.c
@@ -207,6 +207,17 @@ finish:
         return mp;
 }
 
+static int help(void) {
+
+        printf("%s attach VOLUME SOURCEDEVICE [PASSWORD] [OPTIONS]\n"
+               "%s detach VOLUME\n\n"
+               "Attaches or detaches an encrypted block device.\n",
+               program_invocation_short_name,
+               program_invocation_short_name);
+
+        return 0;
+}
+
 int main(int argc, char *argv[]) {
         int r = EXIT_FAILURE;
         struct crypt_device *cd = NULL;
@@ -214,6 +225,11 @@ int main(int argc, char *argv[]) {
         const char *cipher = NULL, *cipher_mode = NULL, *hash = NULL, *name = NULL;
         char *description = NULL, *name_buffer = NULL, *mount_point = NULL;
 
+        if (argc <= 1) {
+                help();
+                return EXIT_SUCCESS;
+        }
+
         if (argc < 3) {
                 log_error("This program requires at least two arguments.");
                 return EXIT_FAILURE;