From ef98fc7fa2c51cd97b5aa4708a55dfa79ea2d128 Mon Sep 17 00:00:00 2001
From: Martin Lund <martin.lund@keep-it-simple.com>
Date: Thu, 12 May 2016 15:44:59 +0200
Subject: [PATCH] Introduced lock on device file

Tio will now test for and obtain an advisory lock on the tty device file
to prevent starting multiple sessions on the same tty device.
---
 src/tty.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/tty.c b/src/tty.c
index a8a7cf8..7618666 100644
--- a/src/tty.c
+++ b/src/tty.c
@@ -27,6 +27,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/param.h>
+#include <sys/file.h>
 #include <fcntl.h>
 #include <termios.h>
 #include <stdbool.h>
@@ -146,6 +147,7 @@ void disconnect_tty(void)
     if (connected)
     {
         color_printf("[tio %s] Disconnected", current_time());
+        flock(fd, LOCK_UN);
         close(fd);
         connected = false;
     }
@@ -184,6 +186,14 @@ int connect_tty(void)
         goto error_isatty;
     }
 
+    /* Lock device file */
+    status = flock(fd, LOCK_EX | LOCK_NB);
+    if ((status == -1) && (errno == EWOULDBLOCK))
+    {
+        printf("Error: Device file is locked by another process\r\n");
+        exit(EXIT_FAILURE);
+    }
+
     /* Flush stale I/O data (if any) */
     tcflush(fd, TCIOFLUSH);