common/common.c, include/common.h: introduce a common method for NUT …

…programs to print_banner_once() [networkupstools#2573]

Signed-off-by: Jim Klimov <[email protected]>

common/common.c

@@ -209,6 +209,26 @@ int banner_is_disabled(void)
 	return value;
 }
 
+int print_banner_once(const char *prog, int even_if_disabled)
+{
+	static int	printed = 0;
+	static int	ret = -1;
+
+	if (printed)
+		return ret;
+
+	if (!banner_is_disabled() || even_if_disabled) {
+		ret = printf("Network UPS Tools %s %s%s\n",
+			prog, UPS_VERSION,
+			even_if_disabled == 2 ? "\n" : "");
+		fflush(stdout);
+		if (ret > 0)
+			printed = 1;
+	}
+
+	return ret;
+}
+
 /* enable writing upslog_with_errno() and upslogx() type messages to
    the syslog */
 void syslogbit_set(void)

include/common.h

@@ -204,6 +204,18 @@ extern const char *UPS_VERSION;
  * hide the NUT tool name+version banners; show them by default */
 int banner_is_disabled(void);
 
+/* Some NUT programs have historically printed their banner at start-up
+ * always, and so did not print one in help()/usage() or handling `-V`
+ * like others did. Now that we have NUT_QUIET_INIT_BANNER, we need a
+ * way to print that banner (regardless of the flag in some cases).
+ * The "even_if_disabled" should be 0 for initial banner of those
+ * programs (so the envvar would hide it), 1 -V case and 2 in -h case
+ * (for a blank line after). As before, the banner is printed to stdout.
+ * Returns the result of printf() involved. Remembers to not print again
+ * if the earlier printf() was successful.
+ */
+int print_banner_once(const char *prog, int even_if_disabled);
+
 /* Normally we can (attempt to) use the syslog or Event Log (WIN32),
  * but environment variable NUT_DEBUG_SYSLOG allows to bypass it, and
  * perhaps keep daemons logging to stderr (e.g. in NUT Integration Test