add osysmon_file.c for reading/monitoring files (like sysfs)
diff --git a/osysmon_file.c b/osysmon_file.c
new file mode 100644
index 0000000..6f826b4
--- /dev/null
+++ b/osysmon_file.c
@@ -0,0 +1,160 @@
+/* Simple Osmocom System Monitor (osysmon): Support for monitoring files */
+
+/* (C) 2018 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+#include <string.h>
+#include <sys/sysinfo.h>
+
+#include <osmocom/vty/vty.h>
+#include <osmocom/vty/command.h>
+
+#include "osysmon.h"
+#include "value_node.h"
+
+/***********************************************************************
+ * Data model
+ ***********************************************************************/
+
+struct osysmon_file {
+ struct llist_head list;
+ struct {
+ const char *name;
+ const char *path;
+ } cfg;
+};
+
+static struct osysmon_file *osysmon_file_find(const char *name)
+{
+ struct osysmon_file *of;
+
+ llist_for_each_entry(of, &g_oss->files, list) {
+ if (!strcmp(of->cfg.name, name))
+ return of;
+ }
+ return NULL;
+}
+
+static struct osysmon_file *osysmon_file_add(const char *name, const char *path)
+{
+ struct osysmon_file *of;
+
+ if (osysmon_file_find(name))
+ return NULL;
+
+ of = talloc_zero(g_oss, struct osysmon_file);
+ OSMO_ASSERT(of);
+ of->cfg.name = talloc_strdup(of, name);
+ of->cfg.path = talloc_strdup(of, path);
+ llist_add_tail(&of->list, &g_oss->files);
+ return of;
+}
+
+static void osysmon_file_destroy(struct osysmon_file *of)
+{
+ llist_del(&of->list);
+ talloc_free(of);
+}
+
+static void osysmon_file_read(struct osysmon_file *of, struct value_node *parent)
+{
+ char buf[512];
+ char *nl;
+ FILE *f;
+
+ f = fopen(of->cfg.path, "r");
+ if (!f) {
+ value_node_add(parent, parent, of->cfg.name, "<NOTFOUND>");
+ return;
+ }
+ if (fgets(buf, sizeof(buf), f) == NULL) {
+ value_node_add(parent, parent, of->cfg.name, "<EMPTY>");
+ return;
+ }
+ buf[sizeof(buf)-1] = '\0';
+ while ((nl = strrchr(buf, '\n')))
+ *nl = '\0';
+ value_node_add(parent, parent, of->cfg.name, buf);
+}
+
+/***********************************************************************
+ * VTY
+ ***********************************************************************/
+
+#define FILE_STR "Configure a file to be monitored/watched\n"
+DEFUN(cfg_file, cfg_file_cmd,
+ "file NAME PATH",
+ FILE_STR "Name of this file-watcher\n" "Path of file in filesystem\n")
+{
+ struct osysmon_file *of;
+ of = osysmon_file_add(argv[0], argv[1]);
+ if (!of) {
+ vty_out(vty, "Couldn't add file-watcher, maybe it exists?%s", VTY_NEWLINE);
+ return CMD_WARNING;
+ }
+ return CMD_SUCCESS;
+}
+
+DEFUN(cfg_no_file, cfg_no_file_cmd,
+ "no file NAME",
+ NO_STR FILE_STR "Name of this file-watcher\n")
+{
+ struct osysmon_file *of;
+ of = osysmon_file_find(argv[0]);
+ if (!of) {
+ vty_out(vty, "Cannot find file-watcher for '%s'%s", argv[0], VTY_NEWLINE);
+ return CMD_WARNING;
+ }
+ osysmon_file_destroy(of);
+ return CMD_SUCCESS;
+}
+
+
+static void osysmon_file_vty_init(void)
+{
+ install_element(CONFIG_NODE, &cfg_file_cmd);
+ install_element(CONFIG_NODE, &cfg_no_file_cmd);
+}
+
+/***********************************************************************
+ * Runtime Code
+ ***********************************************************************/
+
+/* called once on startup before config file parsing */
+int osysmon_file_init()
+{
+ osysmon_file_vty_init();
+ return 0;
+}
+
+/* called periodically */
+int osysmon_file_poll(struct value_node *parent)
+{
+ struct value_node *vn_file;
+ struct osysmon_file *of;
+
+ vn_file = value_node_add(parent, parent, "file", NULL);
+
+ llist_for_each_entry(of, &g_oss->files, list)
+ osysmon_file_read(of, vn_file);
+
+ return 0;
+}