example_range.cpp

#include <unistd.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <fcntl.h>  /* values for fchmodat */

#include <limits>
#include <ctime>
#include <cassert>
#include <fstream>

using TimeSpec = struct ::timespec;

const int MaxNanoseconds = 100'000'000;

TimeSpec const MaxTS = {std::numeric_limits<std::time_t>::max(), MaxNanoseconds - 1};
TimeSpec const MinTS = {std::numeric_limits<std::time_t>::min(), 0};

bool operator==(TimeSpec const& L, TimeSpec const& R) {
  return L.tv_sec == R.tv_sec && L.tv_nsec == R.tv_nsec;
}

bool set_last_write_time(const char* file, TimeSpec const& TS) {
  TimeSpec tbuf[2];
  tbuf[0].tv_sec = 0;
  tbuf[0].tv_nsec = UTIME_OMIT;
  tbuf[1] = TS;
  return (::utimensat(AT_FDCWD, file, tbuf, 0) != -1);
}

TimeSpec get_last_write_time(const char* file) {
  struct ::stat st;
  int exit_code = ::stat(file, &st);
  assert(exit_code == 0);
  return st.st_mtim;
}

int main() {
  const char* filename = "/tmp/foo";
  std::ofstream out(filename);
  out.close();
  assert(set_last_write_time(filename, MaxTS));
  assert(get_last_write_time(filename) == MaxTS);
  assert(set_last_write_time(filename, MinTS));
  assert(get_last_write_time(filename) == MinTS);
}