Fix prototypes for ifctrstat(-linux)

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

cmd/ifctrstat-linux.c

@@ -17,7 +17,8 @@
 #include <limits.h>
 #include <stdio.h>
 #include <string.h>
-#include "multicall.h"
+#include "cmd/multicall.h"
+#include "cmd/ifctrstat-linux.h"
 
 struct counter_desc {
 	const char *name;
@@ -41,7 +42,7 @@ counter_compare(const void *key, const void *candidate)
 	return strcasecmp((const char *)key, ((struct counter_desc *)candidate)->name);
 }
 
-char *
+const char *
 read_counter(const char *interface, const char *counter)
 {
 	FILE *fp;

cmd/ifctrstat-linux.h

@@ -0,0 +1,22 @@
+/*
+ * cmd/ifctrstat-linux.c
+ * Purpose: Implement ifctrstat system-specific routines for Linux
+ *
+ * Copyright (c) 2021 Maximilian Wilhelm <max@sdn.clinic>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+
+#ifndef IFUPDOWN_IFCTRSTAT_LINUX__H__GUARD
+#define IFUPDOWN_IFCTRSTAT_LINUX__H__GUARD
+
+extern const char * read_counter(const char *interface, const char *counter);
+
+#endif

cmd/ifctrstat.c

@@ -20,12 +20,11 @@
 #include <string.h>
 #include "libifupdown/libifupdown.h"
 #include "cmd/multicall.h"
+#include "cmd/ifctrstat-linux.h"
 
 extern struct counter_desc { const char *name; const void *data; } avail_counters[];
 extern int avail_counters_count;
 
-extern const char *read_counter(const char *interface, const char *counter);
-
 static bool show_label = true;
 
 static bool
@@ -96,7 +95,7 @@ ifctrstat_set_nolabel(const char *opt_arg)
 	show_label = false;
 }
 
-int
+static int
 ifctrstat_main(int argc, char *argv[])
 {
 	if (optind >= argc)