Bad output passing integers from parent to child - c

Question

My assignment is to pass integers entered on the command line and pass them through a pipe from parent to child where the integers can be added together and returned to the parent via reaping. All of my integers turn into the number 4 in the child, and the reaped value for sum always returns as the number 1.
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
static int toChild[2];
static int toParent[2];
static int input;
static int output;
int main(int argc, char **argv)
{
pid_t pid;
int status;
int nInts = argc;
// set up pipe
pipe(toChild);
pipe(toParent);
// call fork()
pid = fork();
if (pid == 0) {
close(toChild[1]);
close(toParent[0]);
// -- running in child process --
int sum = 0;
// Receive characters from parent process via pipe
// one at a time, and count them.
// Return sum of numbers.
for (int i=1; i < nInts; i++) {
output = read(toChild[0], &input, sizeof(input));
sum += output;
}
return sum;
close(toChild[0]);
close(toParent[1]);
}
else {
close(toChild[0]);
close(toParent[1]);
// -- running in parent process --
// Send numbers (datatype: int, 4 bytes) from command line arguments
// starting with argv[1] one at a time through pipe to child process.
for (int i=1; i < nInts; i++) {
input = atoi(argv[i]);
write(toChild[1], &input, sizeof(input));
}
waitpid(pid, &status, 0);
if(WIFEXITED(status)){
// Wait for child process to return. Reap child process.
// Receive sum of numbers via the value returned when
// the child process is reaped.
printf("sum = %d\n", WIFEXITED(status));
}
close(toParent[0]);
close(toChild[1]);
return 0;
}
}

Answer 1

output = read(toChild[0], &input, sizeof(input));
sum += output;
You are assigning the return value of read to output. This is the number of bytes read, i.e. sizeof(input) which is 4 on your platform. So you are always increasing sum by 4.
You want:
ssize_t bytes_read = read(toChild[0], &input, sizeof(input));
//check that bytes_read == sizeof(input) here
sum += input;
Also:
printf("sum = %d\n", WIFEXITED(status));
WIFEXITED just says whether the process exited. Use WEXITSTATUS to get the exit status.