/* parent */
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>

int flag;

void sigusr1_handler( int sig )
{
  printf( "caught sigusr1! terminating!\n" );
  flag = 0;
}

int main()
{
  flag = 1;
  signal( SIGUSR1, sigusr1_handler );
  if( fork() == 0 ) execve( "./bin2", NULL, NULL );
  while( flag );
}

/* child */
#include <stdio.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <assert.h>

void sigusr1_handler( int sig )
{
  printf( "sending signal to parent return: %d\n", kill( getppid(), SIGUSR1 ) );
  exit( 0 );
}


int main( int argc, char **argv )
{
  errno = 0;
  signal( SIGUSR1, sigusr1_handler );
  assert( errno == 0 );
  while( 1 );
}