Thread: Keep getting -1 from waitpid

I'm trying to work with foreground/background processes, but seem to keep getting -1 from waitpid and I'm not sure why

Code:

void handleSignal(int signal) {
    printf("terminated by signal %d", signal);
    fflush(stdout);
    exit(signal);
}

struct sigaction sigAct;
    sigAct.sa_handler = handleSignal;
    sigAct.sa_flags = 0;
    sigfillset(&(sigAct.sa_mask));

pid_t spawnpid = -5;
        int childStatus;
        spawnpid = fork();
        
  while(1) {
if (spawnpid == -1) {
//            perror("ERROR: fork()\n");
            printf("failed to start child process\n");
            status = 1;
            fflush(stdout);
            continue;
        } else if (spawnpid == 0) {
            /*
             * inside the child process
             */
            printf("inside child process\n");
        
            sigaction(SIGINT, &sigAct, NULL);
            
            // execute the command
            execvp(command->cmdArgs[0], command->cmdArgs);

            // if reach here then execvp failed
            printf("command not found");
            fflush(stdout);
            status = 1;
        } else if (spawnpid > 1) {
            /*
             * inside the parent process
             */
            printf("inside parent process\n");
            sigaction(SIGINT, &sigAct, NULL);
            
            if (command->background) {
                printf("background pid is %d", spawnpid);
                fflush(stdout);
            } else {
                // wait for child process to finish
                pid_t childpid = waitpid(spawnpid, &childStatus, 0);
                if (childpid == -1) {
                    perror("ERROR: waitpid()\n");
                    status = 1;
                    continue;
                }
                ...
                
                fflush(stdout);
            }
        }
    }
}

The output I keep getting is something like this:

Code:

: ls
inside parent process
inside child process
csXXX_proj3
ERROR: waitpid()
: Interrupted system call
:

The reason I have that while(1) loop is because I want to keep asking the user for input (sort of like a shell). I'm confused about the interrupted system call. I thought that waitpid waits for the child process to finish, and the sigaction was suppose to allow the parent process to do other things while the child process does its own thing.