Transfer int using pipe between N number of process - c

Question

I want to transfer data between multiple child process using pipe() like that :
And that need to work for any number of child process. I want to see child process print the read pipe value and increment this value by one and transfers this values to the next process.
But for now, I have 3 problems :
My child function was call multiple time with the same parameter
Because of that, the file descriptor change and I don't want that.
Every process except the first one get Bad file descriptor with errno
Everything seams to work for the first one because it receives the value from father and have no error when write to the writePipe.
When I run my program, this is my console output
id:0 pipeRead:5 PipeWrite:8
id:0 res:4 value:500
id:1 pipeRead:9 PipeWrite:12
id:2 pipeRead:13 PipeWrite:16
id:1 pipeRead:3 PipeWrite:6
id:2 pipeRead:7 PipeWrite:10
id:1 res:-1 value:0
id:2 pipeRead:3 PipeWrite:6
id:2 res:-1 value:0
Read Error: Bad file descriptor
Read Error: Bad file descriptor
So, here my code attempt
int execChild(int appID, int pipeRead[2], int pipeWrite[2]){
//Before start process, I close read/write that not used here
//Close write of read pipe
close(pipeRead[1]);
//Close read of write pipe
close(pipeWrite[0]);
printf("id:%d pipeRead:%d PipeWrite:%d\n",appID,pipeRead[0],pipeWrite[1]);
int buff=0;
long int res;
res = read(pipeRead[0],&buff,sizeof(int));
if (res==-1) perror("Read Error");
//Close read pipe after used
close(pipeRead[0]);
printf("id:%d res:%ld value:%d\n",appID,res,buff);
//Increment value
buff += 1;
res = write(pipeWrite[1],&buff,sizeof(int));
if(res==-1)perror("Write Error");
//Close write pipe after used
close(pipeWrite[1]);
return 0;
}
int main(int argc, char *argv[]) {
int nbFis = 3;
//Init array of pipeArray with malloc
int* pipeArr[nbFis];
for (int i = 0; i < nbFis; i++)
pipeArr[i] = (int*)malloc(2 * sizeof(int));
for (int i = 0; i < nbFis; i++) // Generate n child
{
//Here we open every inter child pipe
//If the process is 0 we need to open the last pipe of the array
//Else we open the last pipe
if(i==0){
pipe(pipeArr[nbFis-1]);//Open Read Pipe
//To test I inject an int value here to child 0
int value = 500;
write(pipeArr[nbFis-1][1],&value,sizeof(int));//Write value in the pipe
}else{
pipe(pipeArr[i-1]);//Open Read Pipe
}
pipe(pipeArr[i]);//Open Write Pipe
if (fork() == 0) {
//If it's the first child we send the last pipe in the array as read pipe and current pipe as write pipe
//Else we send the previous pipe in the list as read pipe and current pipe as write pipe
if(i==0){
execChild(i,pipeArr[nbFis-1],pipeArr[i]);
}else{
execChild(i,pipeArr[i-1],pipeArr[i]);
}
}
}
//Wait for the end of process and free memory
for (int i = 0; i < nbFis; i++) {
free(pipeArr[i]);
wait(NULL);
}
return 0;
}