watchdog: allow millisecond spec (-t 250ms)

function                                             old     new   delta
packed_usage                                       23069   23113     +44
static.suffixes                                        -      24     +24
watchdog_main                                        147     160     +13
static.V                                               -       1      +1
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 2/0 up/down: 82/0)               Total: 82 bytes

2 files changed, 22 insertions, 14 deletions

diff --git a/include/usage.h b/include/usage.h
index e062c0c02..6a88b6cf1 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -3843,7 +3843,7 @@ USE_FEATURE_RUN_PARTS_FANCY("\n	-l	Prints names of all matching files even when
 #define watch_full_usage \
        "Execute a program periodically" \
        "\n\nOptions:\n" \
-       "        -n      Loop period in seconds - default is 2\n" \
+       "        -n      Loop period in seconds (default 2)\n" \
        "        -t      Don't print header"
 #define watch_example_usage \
        "$ watch date\n" \
@@ -3852,12 +3852,14 @@ USE_FEATURE_RUN_PARTS_FANCY("\n	-l	Prints names of all matching files even when
        "Mon Dec 17 10:31:44 GMT 2000"
 
 #define watchdog_trivial_usage \
-       "[-t seconds] [-F] DEV"
+       "[-t N[ms]] [-F] DEV"
 #define watchdog_full_usage \
        "Periodically write to watchdog device DEV" \
-       "\n\nOptions:\n" \
-       "        -t      Timer period in seconds - default is 30\n" \
-       "        -F      Stay in the foreground and don't fork"
+       "\n\nOptions:" \
+     "\n        -t N    Timer period (default 30)" \
+     "\n        -F      Stay in the foreground and don't fork" \
+     "\n" \
+     "\nUse -t 500ms to specify period in milliseconds"
 
 #define wc_trivial_usage \
        "[OPTION]... [FILE]..."
diff --git a/miscutils/watchdog.c b/miscutils/watchdog.c
index aa367d5ab..14bd44f48 100644
--- a/miscutils/watchdog.c
+++ b/miscutils/watchdog.c
@@ -16,7 +16,9 @@
 static void watchdog_shutdown(int ATTRIBUTE_UNUSED sig) ATTRIBUTE_NORETURN;
 static void watchdog_shutdown(int ATTRIBUTE_UNUSED sig)
 {
-        write(3, "V", 1);       /* Magic, see watchdog-api.txt in kernel */
+        static const char V = 'V';
+
+        write(3, &V, 1);        /* Magic, see watchdog-api.txt in kernel */
         if (ENABLE_FEATURE_CLEAN_UP)
                 close(3);
         exit(0);
@@ -26,14 +28,20 @@ int watchdog_main(int argc, char **argv);
 int watchdog_main(int argc, char **argv)
 {
         unsigned opts;
-        unsigned timer_duration = 30; /* Userspace timer duration, in seconds */
+        unsigned timer_duration = 30000; /* Userspace timer duration, in milliseconds */
         char *t_arg;
 
         opt_complementary = "=1"; /* must have 1 argument */
         opts = getopt32(argv, "Ft:", &t_arg);
 
-        if (opts & OPT_TIMER)
-                timer_duration = xatou(t_arg);
+        if (opts & OPT_TIMER) {
+                static const struct suffix_mult suffixes[] = {
+                        { "ms", 1 },
+                        { "", 1000 },
+                        { }
+                };
+                timer_duration = xatou_sfx(t_arg, suffixes);
+        }
 
         if (!(opts & OPT_FOREGROUND)) {
                 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
@@ -50,10 +58,8 @@ int watchdog_main(int argc, char **argv)
                  * Make sure we clear the counter before sleeping, as the counter value
                  * is undefined at this point -- PFM
                  */
-                write(3, "", 1);
-                sleep(timer_duration);
+                write(3, "", 1); /* write zero byte */
+                usleep(timer_duration * 1000L);
         }
-
-        watchdog_shutdown(0);
-        /* return EXIT_SUCCESS; */
+        return EXIT_SUCCESS; /* - not reached, but gcc 4.2.1 is too dumb! */
 }