native: set optional path with unix socket option

fixes #1045

boards/native/drivers/native-uart0.c

@@ -149,7 +149,13 @@ int init_unix_socket(void)
     }
 
     sa.sun_family = AF_UNIX;
+
+    if (_native_unix_socket_path != NULL) {
+        snprintf(sa.sun_path, sizeof(sa.sun_path), "%s", _native_unix_socket_path);
+    }
+    else {
         snprintf(sa.sun_path, sizeof(sa.sun_path), "/tmp/riot.tty.%d", _native_pid);
+    }
     unlink(sa.sun_path); /* remove stale socket */
     if (bind(s, (struct sockaddr *)&sa, SUN_LEN(&sa)) == -1) {
         err(EXIT_FAILURE, "init_unix_socket: bind");

cpu/native/include/native_internal.h

@@ -79,6 +79,7 @@ extern ucontext_t *_native_cur_ctx, *_native_isr_ctx;
 extern const char *_progname;
 extern char **_native_argv;
 extern pid_t _native_pid;
+extern const char *_native_unix_socket_path;
 
 #ifdef MODULE_UART0
 #include <sys/select.h>

cpu/native/startup.c

@@ -44,6 +44,7 @@ int _native_null_out_file;
 const char *_progname;
 char **_native_argv;
 pid_t _native_pid;
+const char *_native_unix_socket_path = NULL;
 
 /**
  * initialize _native_null_in_pipe to allow for reading from stdin
@@ -160,7 +161,7 @@ void usage_exit(void)
 #endif
 
 #ifdef MODULE_UART0
-    real_printf(" [-t <port>|-u]");
+    real_printf(" [-t <port>|-u [path]]");
 #endif
 
     real_printf(" [-d] [-e|-E] [-o]\n");
@@ -177,6 +178,7 @@ void usage_exit(void)
 #ifdef MODULE_UART0
     real_printf("\
 -u      redirect stdio to UNIX socket\n\
+        if no path is given /tmp/riot.tty.PID is used\n\
 -t      redirect stdio to TCP socket\n");
 #endif
 
@@ -272,6 +274,11 @@ __attribute__((constructor)) static void startup(int argc, char **argv)
             if (strcmp(stderrtype, "stdio") == 0) {
                 stderrtype = "null";
             }
+
+            /* parse optional path */
+            if ((argp + 1 < argc) && (argv[argp + 1][0] != '-')) {
+                _native_unix_socket_path = argv[++argp];
+            }
         }
 #endif
         else {