//multiply a[2][3] * b[3][4] = c[2][4]
//with fork
//each child completes one c[2][4]'s row

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>

main()
{
  int a[2][3]={1,2,3, 
	       4,5,6};
  int b[3][4]={1,2,3,4,
	       5,6,7,8,
	       9,10,11,12};
  int c[2][4];
  int i,j;
  int m[4];	//for the calculation
  int n;	//common 3
  int pid;	//fork
  int pipefd[2];
  int w,r;
  char buff[100];
  char str[100+1]={'\0'};
  int temp;
   
  for(i=0;i<2;i++)
  {
    pipe(pipefd);
      if(pipefd<0)
	printf("Pipe error\n");
    pid=fork();
    if(pid==-1)
    {
      printf("Can't fork\n");
    }
    if(pid==0)//child
    {
      for(n=0;n<3;n++){m[n]=0;}	//initialize m[4]
      for(j=0;j<4;j++)
      {
	for(n=0;n<3;n++)
	{
	  temp=temp+a[i][n]*b[n][j];
	}
	m[j]=temp;
	sprintf(str,"%d ",m[j]);
	w=write(pipefd[1],str,sizeof(str));
	if(w!=sizeof(str))
	  printf("\nWrite error");
      }
      exit(0);
    }
    if(pid>0)//parent
    {
      wait(0);
      r=read(pipefd[0], buff, sizeof(buff));
      if(r<=0)
	printf("\nRead Error");
      for(n=0;n<3;n++)
      {
	sscanf(m[n],"%s",buff);	//or otherwise
	c[i][n]=m[n];	//give to c each time a row
      }
    }
    
  }
  printf("C:\n");
  for(i=0;i<2;i++)
  {
    for(j=0;j<4;j++)
    {
      printf("%d\t",c[i][j]);
    }
    printf("\n");
  }	       
}

example.c: In function ‘main’:
example.c:61:2: warning: passing argument 1 of ‘sscanf’ makes pointer from integer without a cast [enabled by default]
/usr/include/stdio.h:450:12: note: expected ‘const char * __restrict__’ but argument is of type ‘int’