nano arbitrary-baud.c
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <linux/termios.h>

int ioctl(int d, int request, ...);

int main(int argc, char *argv[])
{
 struct termios2 t;
 int fd,baud;

 if (argc != 3)
   {
     fprintf(stderr,"usage: %s <device> <baud>\n", argv[0]);
     return 1;
   }

 fd = open(argv[1], O_RDWR | O_NOCTTY | O_NDELAY);

 if (fd == -1)
     {
       fprintf(stderr, "error opening %s: %s", argv[1], strerror(errno));
       return 2;
     }

 baud = atoi(argv[2]);

 if (ioctl(fd, TCGETS2, &t))
   {
     perror("TCGETS2");
     return 3;
   }

 t.c_cflag &= ~CBAUD;
 t.c_cflag |= BOTHER;
 t.c_ispeed = baud;
 t.c_ospeed = baud;

 if (ioctl(fd, TCSETS2, &t))
   {
     perror("TCSETS2");
     return 4;
   }

 if (ioctl(fd, TCGETS2, &t))
   {
     perror("TCGETS2");
     return 5;
   }

 printf("actual speed reported %d\n", t.c_ospeed);
 return 0;
}
gcc -o arbitrary-baud arbitrary-baud.c

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