8.16.c

#include <errno.h>
#include <sys/time.h>
#include "apue.h"

#if defined(SOLARIS)
#include <limits.h>
#elif defined(BSD)
#include <sys/param.h>
#endif

unsigned long long count;
struct timeval end;

void checktime(char *str) {
  struct timeval tv;

  gettimeofday(&tv, NULL);
  if (tv.tv_sec >= end.tv_sec && tv.tv_usec >= end.tv_usec) {
    printf("%s count = %lld\n", str, count);
    exit(0);
  }
}

int main(int argc, char *argv[]) {
  pid_t pid;
  char *s;
  int nzero, ret;
  int adj = 0;
  setbuf(stdout, NULL);
#if defined(NZERO)
  nzero = NZERO;
#elif defined(_SC_NZERO)
  nzero = sysconf(_SC_NZERO);
#else
#error NZERO undefined
#endif
  printf("NZERO = %d\n", nzero);
  if (argc == 2) {
    adj = strtol(argv[1], NULL, 10);
  }
  gettimeofday(&end, NULL);
  end.tv_sec += 10;

  if ((pid = fork()) < 0) {
    err_sys("fork failed");
  } else if (pid == 0) {
    s = "child";
    printf("current nice value in child is %d, adjusting by %d\n",
           nice(0) + nzero, adj);
    errno = 0;
    if ((ret = nice(adj)) == -1 && errno != 0) {
      err_sys("child set scheduling priority");
    }
    printf("now child nice value is %d\n", nice(0) + nzero);
  } else {
    s = "parent";
    printf("current nice value in parent is %d\n", nice(0) + nzero);
  }
  for (;;) {
    if (++count == 0) {
      err_quit("%s counter wrap", s);
    }
    checktime(s);
  }
}