Add option --no-tty-restore / -N that omits tty_restore() call #334

On exit, do not reset the tty device settings to the state they were in
before the program started.
This is effective when sending characters at a low baud rate and then
immediately exiting, to ensure that the last character is output
correctly.

README.md

@@ -122,6 +122,7 @@ Options:
       --exclude-drivers <pattern>        Exclude drivers by pattern
       --exclude-tids <pattern>           Exclude topology IDs by pattern
   -n, --no-reconnect                     Do not reconnect
+  -N, --no-tty-restore                   Do not restore initial TTY device settings
   -e, --local-echo                       Enable local echo
       --input-mode normal|hex|line       Select input mode (default: normal)
       --output-mode normal|hex|hexN      Select output mode (default: normal)

examples/config/config

@@ -19,6 +19,7 @@ output-delay = 0
 output-line-delay = 0
 auto-connect = direct
 no-reconnect = false
+no-tty-restore = false
 local-echo = false
 input-mode = normal
 output-mode = normal

man/tio.1.in

@@ -123,6 +123,14 @@ Do not reconnect.
 This means that tio will exit if it fails to connect to device or an
 established connection is lost.
 
+.TP
+.BR \-n ", " \-\-no\-tty\-restore
+
+Do not restore initial TTY device settings.
+
+This means that tio will exit without trying to restore TTY device
+settings that existed when tio was started.
+
 .TP
 .BR \-e ", " "\-\-local\-echo
 

man/tio.1.txt

@@ -94,6 +94,12 @@ OPTIONS
 
               This means that tio will exit if it fails to connect to device or an established connection is lost.
 
+       -N, --no-tty-restore
+
+              Do not restore initial TTY device settings.
+
+              This means that tio will exit without trying to restore TTY device settings that existed when tio was started.
+
        -e, --local-echo
 
               Enable local echo.

src/bash-completion/tio.in

@@ -23,6 +23,7 @@ _tio()
              --exclude-drivers \
              --exclude-tids \
           -n --no-reconnect \
+          -N --no-tty-restore \
           -e --local-echo \
           -l --log \
              --log-file \

src/configfile.c

@@ -196,6 +196,7 @@ static void config_parse_keys(GKeyFile *key_file, char *group)
     config_get_string(key_file, group, "exclude-drivers", &option.exclude_devices, NULL);
     config_get_string(key_file, group, "exclude-tids", &option.exclude_devices, NULL);
     config_get_bool(key_file, group, "no-reconnect", &option.no_reconnect);
+    config_get_bool(key_file, group, "no-tty-restore", &option.no_tty_restore);
     config_get_bool(key_file, group, "local-echo", &option.local_echo);
     config_get_string(key_file, group, "input-mode", &string, "normal", "hex", "line", NULL);
     if (string != NULL)

src/options.c

@@ -82,6 +82,7 @@ struct option_t option =
     .dcd_pulse_duration = 100,
     .ri_pulse_duration = 100,
     .no_reconnect = false,
+    .no_tty_restore = false,
     .auto_connect = AUTO_CONNECT_DIRECT,
     .log = false,
     .log_append = false,
@@ -153,6 +154,7 @@ void option_print_help(char *argv[])
     printf("      --exclude-drivers <pattern>        Exclude drivers by pattern\n");
     printf("      --exclude-tids <pattern>           Exclude topology IDs by pattern\n");
     printf("  -n, --no-reconnect                     Do not reconnect\n");
+    printf("  -N, --no-tty-restore                   Do not restore initial TTY device settings\n");
     printf("  -e, --local-echo                       Enable local echo\n");
     printf("      --input-mode normal|hex|line       Select input mode (default: normal)\n");
     printf("      --output-mode normal|hex|hexN      Select output mode (default: normal)\n");
@@ -844,6 +846,7 @@ void option_parse_mappings(const char *map)
 
 void options_print()
 {
+    /* note: negative true/false settings are rephrased as affirmative no/yes. */
     tio_printf(" Device: %s", device_name);
     tio_printf(" Baudrate: %u", option.baudrate);
     tio_printf(" Databits: %d", option.databits);
@@ -858,6 +861,7 @@ void options_print()
     tio_printf(" Output line delay char: %s", option.output_line_delay_char == '\r' ? "cr" : "lf");
     tio_printf(" Automatic connect strategy: %s", option_auto_connect_state_to_string(option.auto_connect));
     tio_printf(" Automatic reconnect: %s", option.no_reconnect ? "true" : "false");
+    tio_printf(" TTY device settings restore: %s", option.no_tty_restore ? "true" : "false");
     // clang-format off
     tio_printf(" Pulse duration: DTR=%d RTS=%d CTS=%d DSR=%d DCD=%d RI=%d", option.dtr_pulse_duration,
                                                                             option.rts_pulse_duration,
@@ -933,6 +937,7 @@ void options_parse(int argc, char *argv[])
             {"exclude-drivers",      required_argument, 0, OPT_EXCLUDE_DRIVERS     },
             {"exclude-tids",         required_argument, 0, OPT_EXCLUDE_TIDS        },
             {"no-reconnect",         no_argument,       0, 'n'                     },
+            {"no-tty-restore",       no_argument,       0, 'N'                     },
             {"local-echo",           no_argument,       0, 'e'                     },
             {"timestamp",            no_argument,       0, 't'                     },
             {"timestamp-format",     required_argument, 0, OPT_TIMESTAMP_FORMAT    },
@@ -967,7 +972,7 @@ void options_parse(int argc, char *argv[])
         int option_index = 0;
 
         /* Parse argument using getopt_long */
-        c = getopt_long(argc, argv, "b:d:f:s:p:o:O:a:netLlS:m:c:xrvh", long_options, &option_index);
+        c = getopt_long(argc, argv, "b:d:f:s:p:o:O:a:nNetLlS:m:c:xrvh", long_options, &option_index);
 
         /* Detect the end of the options */
         if (c == -1)
@@ -1041,6 +1046,10 @@ void options_parse(int argc, char *argv[])
                 option.no_reconnect = true;
                 break;
 
+            case 'N':
+                option.no_tty_restore = true;
+                break;
+
             case 'e':
                 option.local_echo = true;
                 break;

src/options.h

@@ -62,6 +62,7 @@ struct option_t
     int dcd_pulse_duration;
     int ri_pulse_duration;
     bool no_reconnect;
+    bool no_tty_restore;
     auto_connect_t auto_connect;
     bool log;
     bool log_append;

src/tty.c

@@ -2706,10 +2706,13 @@ int tty_connect(void)
         rs485_mode_enable(device_fd);
     }
 
-    /* Make sure we restore tty settings on exit */
+    /* Make sure we restore tty settings on exit unless ordered to keep current settings */
     if (first)
+    {
+        if (option.no_tty_restore == false)
         {
             atexit(&tty_restore);
+        }
         first = false;
     }