Linux receive signal break for ttycontrol program

Question

I would like to receive SIGINT if my process controlling /dev/ttyS2 receives BREAK on a serial port. I run this program from a shell. From what I discovered only "the terminal is the controlling terminal of a foreground process group, it will cause a SIGINT to be sent to this foreground process group" I tried make process making controller of terminal but it fails.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h> 
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#include <string.h>

#define BAUDRATE B115200
#define MODEMDEVICE "/dev/ttyS2"
#define _POSIX_SOURCE 1 /* POSIX compliant source */
#define FALSE 0
#define TRUE 1


__sighandler_t sighandle(int signum, __sighandler_t h) { 
    fprintf(stderr, "BREAK DETECTED\n"); 
    signal(SIGINT, (__sighandler_t) sighandle); 
    return SIG_IGN; 
}
volatile int STOP=FALSE; 

int    main()
{
    int fd,c, res;
    struct termios oldtio,newtio;
    char buf[255];
    pid_t  pid; 
    signal(SIGINT, (__sighandler_t) sighandle);

    fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY ); 
    if (fd <0) {perror(MODEMDEVICE); return (-1); }


    tcgetattr(fd,&oldtio); /* save current port settings */

    memset(&newtio, 0,sizeof(newtio));
    newtio.c_cflag |= BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD | BRKINT;
    newtio.c_iflag &= ~IGNBRK ;
    newtio.c_oflag = 0;

    /* set input mode (non-canonical, no echo,...) */
    newtio.c_lflag = 0;

    newtio.c_cc[VTIME]    = 0;   /* inter-character timer unused */
    newtio.c_cc[VMIN]     = 1;   /* blocking read until 5 chars received */

    tcflush(fd, TCIFLUSH);
    tcsetattr(fd,TCSANOW,&newtio);

    if( ioctl(fd, TIOCSCTTY, 1) <0 )
    {
        printf("Error number: %d\n", errno);
    }
   if ( tcsetpgrp(fd, tcgetpgrp(0) ) < 0 )
   {
   syslog(LOG_PERROR,"tcsetpgrp failed: %d " ,errno);
   syslog(LOG_PERROR,"EBADF is %d " ,EBADF);    
   syslog(LOG_PERROR,"EINVAL is %d " ,EINVAL);
   syslog(LOG_PERROR,"ENOTTY is %d " ,ENOTTY);    
   syslog(LOG_PERROR,"EPERM is %d " ,EPERM);  
   }
    while (STOP==FALSE) {       /* loop for input */
        res = read(fd,buf,255);   /* returns after 5 chars have been input */
        buf[res]=0;               /* so we can printf... */

        printf(":%s:%d\n", buf, res);
        if (buf[0]=='z') {STOP=TRUE;}
    }
    tcsetattr(fd,TCSANOW,&oldtio);
    return 0;
}

Answer 1

#define _POSIX_SOURCE 1 has no effect unless it precedes the #includes.

With a C99 compiler, you may #include <stdbool.h> instead of #define your own TRUE and FALSE.

/* from signal.h, */
typedef void(*sighandler_t)(int);
/* which means the handler must be declared thusly */
void sighandle(int);
/* as a result, no casting is necessary */
sighandler_t p_sighandle = &sighandle;

The foreground process group is set by tcsetpgrp, which you appear to be missing.

Answer 2

I finally found answer to my problem. I am using custom board so it don't have to work always but when serial port is configured correctly user can get number of breaks by serial port by cat /proc/tty/device/serial, that kind of functionality I was hoping to get