How to make three processes work in C/C++ -

i have make 3 processes a, b , c use shared memory. , b write 100 integers in shared memory, , c reads them , writes them binary file. made, doesn't work properly. include <stdio.h>, <math.h>, <fcntl.h> , <time.h>. how make work?

struct sync {     int n;     int lock;     int generated;     char process; } *b;  int testandset(int* lockptr) {     int oldvalue = *lockptr;      return 0 != oldvalue; }  int main() {     struct sync buff;     int pid, ppid, fp, i;      srand(time(null));      b = (struct sync*)malloc(666);     b->n = 0;     b->lock = 0;     b->generated = 0;      = 0;      printf("generating numbers\n");      pid = fork();      if (0 == pid)     {         while (100 >= b->generated)         {             while (testandset(&(b->lock)))             {              }              buff.n = rand() % 1001;             buff.process = 'a';              fp = open("db", o_rdwr | o_append);              if (-1 == fp)                 fp = open("db", o_creat);              write(fp, &buff, sizeof(struct sync));                    close(fp);              b->generated++;             b->lock = 0;         }     }      if (0 < pid)     {         ppid = fork();          if (0 == ppid)          {             while (100 >= b->generated)             {                 while (testandset(&(b->lock)))                 {                  }                  buff.n = rand() % 1001;                 buff.process = 'b';                  printf("no: %d %d \n", ++i, buff.n);                  fp = open( "db", o_rdwr | o_append );                  if (-1 == fp)                     fp = open("db", o_creat);                  write(fp, &buff, sizeof(struct sync));                        close(fp);                  b->generated++;                 b->lock = 0;             }         }          if (0 < ppid)         {             wait();              = 0;              fp = open("db", o_rdonly, 0755);              printf("reading file\n");              while (read(fp, &buff, sizeof(struct sync)))             {                 if ('a' == buff.process)                     i++;             }              close(fp);              int vals[i];              = 0;              fp = open("db", o_rdonly, 0666);              while (read(fp, &buff, sizeof(struct sync)))             {                 if ('a' == buff.process)                     vals[i++] = buff.n;             }              close(fp);              fp = open("db", o_rdonly, 0455);              int i;              for(i = 0; < i; i++)                 write((const void*) &vals[i],sizeof(int),1,fp);         }          wait();     }      return 0; } 

files not reliable mutliprocess sharing information (and editing @ same time), you'd rather use real database in transaction mode or use ipc http://www.cs.cf.ac.uk/dave/c/node27.html. or maybe re-design , use threads , mutex.