alarming: make native nagios support to dhcpd-pools

This commit makes integrating the command with nagios much easier.

$ dhcpd-pools -c dhcpd.conf -l dhcpd.leases --critical 80 --warning 75
CRITICAL: dhcpd-pools: Ranges; crit: 14 warn: 22 ok: 220 Shared nets; crit: 1 warn: 0 ok: 4

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

src/other.c

@@ -136,6 +136,28 @@ char *safe_strdup(const char *restrict str)
 	return ret;
 }
 
+/* Return percentage value */
+double strtod_or_err(const char *str, const char *errmesg)
+{
+	double num;
+	char *end = NULL;
+
+	if (str == NULL || *str == '\0')
+		goto err;
+	errno = 0;
+	num = strtod(str, &end);
+
+	if (errno || str == end || (end && *end))
+		goto err;
+
+	return num;
+ err:
+	if (errno)
+		err(EXIT_FAILURE, "%s: '%s'", errmesg, str);
+
+	errx(EXIT_FAILURE, "%s: '%s'", errmesg, str);
+}
+
 void flip_ranges(struct range_t *restrict ranges, struct range_t *restrict tmp_ranges)
 {
 	unsigned int i = num_ranges - 1, j;
@@ -237,6 +259,9 @@ This is ISC dhcpd pools usage analyzer.\n\
   -o, --output=FILE      output into a file\n\
   -L, --limit=NR         output limit mask 77 - 00\n");
 	fprintf(out, "\
+      --warning=PERC     set warning alarming limit\n\
+      --critical=PERC    set critical alarming limit\n");
+	fprintf(out, "\
   -v, --version          version information\n\
   -h, --help             this screen\n\
 \n\