[andreyv]

In C, and many other languages, the file stream error state is saved after each operation, so you can skip error checking on every output line and only do

  if (fflush(stdout) != 0 || ferror(stdout) != 0)
  {
    perror("stdout");
    return EXIT_FAILURE;
  }

at the end of the program. The same should be done for stderr as well.

In GNU programs you can use atexit(close_stdout) to do this automatically.

[Asooka]

I wish this post were higher up, since it shows the idiomatic way to deal with that problem, unlike the article. Obviously the designers of the Unix i/o interface thought about this and provided for a simple way of handling it.

[PennRobotics]

Would perror() return the first/oldest error or the last?

[andreyv]

Right — ferror() does not set errno, and so perror() is not appropriate here. fprintf(stderr, ...) would be better.