example_n_useful/utils/ttywrite.c

   1 /*
   2  * Writes the command line arguments (or standard input) to a tty using
   3  * the TIOCSTI ioctl. This will typically require root access, the
   4  * setuid bit set on this binary (danger!), or on Linux the appropriate
   5  * capability granted. The bytes will be written as given, except on the
   6  * command line a space will be written between each argument, and a
   7  * final newline written if the -N option is set.
   8  *
   9  * Notable codes (via ttytest.c testing on Mac OS X) include:
  10  *
  11  *   sudo ttywrite $(tty) $'\003'   # SIGINT
  12  *   sudo ttywrite $(tty) $'\004'   # EOF
  13  *   sudo ttywrite $(tty) $'\014'   # clear (control+l)
  14  *   sudo ttywrite $(tty) $'\020'   # SIGINFO
  15  *   sudo ttywrite $(tty) $'\020'   # SIGTSTP
  16  *   sudo ttywrite $(tty) $'\020'   # SIGQUIT
  17  */
  18
  19 #include <sys/ioctl.h>
  20 #include <sys/stat.h>
  21 #if defined(__FreeBSD__) || defined(__OpenBSD__)
  22 #include <sys/ttycom.h>
  23 #endif
  24
  25 #include <err.h>
  26 #include <fcntl.h>
  27 #include <getopt.h>
  28 #include <stdbool.h>
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <sysexits.h>
  32 #include <unistd.h>
  33
  34 // https://github.com/thrig/goptfoo
  35 #include <goptfoo.h>
  36
  37 void emit_help(void);
  38 void tty_write(int fd, int argc, char *argv[], useconds_t delay);
  39
  40 useconds_t Flag_Delay = 0;      // -d delay in milliseconds
  41 bool Flag_Newline = false;      // -N
  42
  43 int main(int argc, char *argv[])
  44 {
  45     int ch, fd;
  46
  47     while ((ch = getopt(argc, argv, "d:h?N")) != -1) {
  48         switch (ch) {
  49         case 'd':
  50             /* KLUGE useconds_t is "unsigned int" on *BSD at time of
  51              * writing so assume that as max for usleep(3) */
  52             Flag_Delay = (useconds_t)
  53                 flagtoul(ch, optarg, 0UL,
  54                          (unsigned long) UINT_MAX / 1000) * 1000;
  55             break;
  56         case 'N':
  57             Flag_Newline = true;
  58             break;
  59         case 'h':
  60         case '?':
  61         default:
  62             emit_help();
  63             /* NOTREACHED */
  64         }
  65     }
  66     argc -= optind;
  67     argv += optind;
  68
  69     if (argc < 1)
  70         emit_help();
  71
  72     if ((fd = open(*argv, O_WRONLY)) == -1)
  73         err(EX_IOERR, "could not open '%s'", *argv);
  74     tty_write(fd, --argc, ++argv, Flag_Delay);
  75     close(fd);
  76
  77     exit(EXIT_SUCCESS);
  78 }
  79
  80 void emit_help(void)
  81 {
  82     fprintf(stderr, "Usage: ttywrite [-d delayms] [-N] dev [command...|-]\n");
  83     exit(EX_USAGE);
  84 }
  85
  86 void tty_write(int fd, int argc, char *argv[], useconds_t delay)
  87 {
  88     int c;
  89
  90     if (argc == 0 || ((*argv)[0] == '-' && (*argv)[1] == '\0')) {
  91         while ((c = getchar()) != EOF) {
  92             ioctl(fd, TIOCSTI, &c);
  93             if (delay)
  94                 usleep(delay);
  95         }
  96         if (ferror(stdin)) {
  97             err(EX_IOERR, "error reading from standard input");
  98         }
  99         return;
 100     }
 101
 102     while (*argv) {
 103         while (**argv != '\0') {
 104             ioctl(fd, TIOCSTI, (*argv)++);
 105             if (delay)
 106                 usleep(delay);
 107         }
 108         ioctl(fd, TIOCSTI, " ");
 109         argv++;
 110     }
 111
 112     if (Flag_Newline)
 113         ioctl(fd, TIOCSTI, "\n");
 114 }