diff -r 8b5e8f1e172d -r a03b6dac5398 thermferm/lock.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/thermferm/lock.c	Sun May 25 22:06:56 2014 +0200
@@ -0,0 +1,132 @@
+/*****************************************************************************
+ * Copyright (C) 2014
+ *   
+ * Michiel Broek <mbroek at mbse dot eu>
+ *
+ * This file is part of the mbsePi-apps
+ *
+ * This 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, or (at your option) any
+ * later version.
+ *
+ * mbsePi-apps 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 EC-65K; see the file COPYING.  If not, write to the Free
+ * Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *****************************************************************************/
+
+#include "thermferm.h"
+
+/*
+ *  Put a lock on this program.
+ */
+int lockprog(char *name)
+{
+    char    *tempfile, *lockfile;
+    FILE    *fp;
+    pid_t   oldpid;
+
+    tempfile = calloc(PATH_MAX, sizeof(char));
+    lockfile = calloc(PATH_MAX, sizeof(char));
+
+    snprintf(tempfile, PATH_MAX, "/var/run/%s.tmp", name);
+    snprintf(lockfile, PATH_MAX, "/var/run/%s.pid", name);
+
+    if ((fp = fopen(tempfile, "w")) == NULL) {
+	perror(name);
+	printf("Can't create lockfile \"%s\"\n", tempfile);
+	free(tempfile);
+	free(lockfile);
+	return 1;
+    }
+    fprintf(fp, "%10u\n", getpid());
+    fclose(fp);
+
+    while (TRUE) {
+	if (link(tempfile, lockfile) == 0) {
+	    unlink(tempfile);
+	    free(tempfile);
+	    free(lockfile);
+	    return 0;
+	}
+	if ((fp = fopen(lockfile, "r")) == NULL) {
+	    perror(name);
+	    printf("Can't open lockfile \"%s\"\n", tempfile);
+	    unlink(tempfile);
+	    free(tempfile);
+	    free(lockfile);
+	    return 1;
+	}
+	if (fscanf(fp, "%u", &oldpid) != 1) {
+	    perror(name);
+	    printf("Can't read old pid from \"%s\"\n", tempfile);
+	    fclose(fp);
+	    unlink(tempfile);
+	    free(tempfile);
+	    free(lockfile);
+	    return 1;
+	}
+	fclose(fp);
+	if (kill(oldpid,0) == -1) {
+	    if (errno == ESRCH) {
+		printf("Stale lock found for pid %u\n", oldpid);
+		unlink(lockfile);
+		/* no return, try lock again */  
+	    } else {
+		perror(name);
+		printf("Kill for %u failed\n",oldpid);
+		unlink(tempfile);
+		free(tempfile);
+		free(lockfile);
+		return 1;
+	    }
+	} else {
+	    printf("Another %s is already running, pid=%u\n", name, oldpid);
+	    unlink(tempfile);
+	    free(tempfile);
+	    free(lockfile);
+	    return 1;
+	}
+    }
+}
+
+
+
+void ulockprog(char *name)
+{
+    char	    *lockfile;
+    pid_t	    oldpid;
+    FILE	    *fp;
+
+    lockfile = calloc(PATH_MAX, sizeof(char));
+    snprintf(lockfile, PATH_MAX, "/var/run/%s.pid", name);
+
+    if ((fp = fopen(lockfile, "r")) == NULL) {
+	syslog(LOG_NOTICE, "Can't open lockfile \"%s\"", lockfile);
+	free(lockfile);
+	return;
+    }
+
+    if (fscanf(fp, "%u", &oldpid) != 1) {
+	syslog(LOG_NOTICE, "Can't read old pid from \"%s\"", lockfile);
+	fclose(fp);
+	unlink(lockfile);
+	free(lockfile);
+	return;
+    }
+
+    fclose(fp);
+
+    if (oldpid == getpid()) {
+	(void)unlink(lockfile);
+    }
+
+    free(lockfile);
+}
+
+