lib: add fileutils file with stream error checking facility

The close_stream() is copied from GNU lib. Inspiration to do this
is talk by Jim Meyering - Goodbye World! The perils of relying on
output streams in C.

Reference: http://www.irill.org/events/ghm-gnu-hackers-meeting/videos/jim-meyering-goodbye-world-the-perils-of-relying-on-output-streams-in-c
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

lib/fileutils.c

@@ -0,0 +1,43 @@
+#include <errno.h>
+#include <error.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "nls.h"
+
+int close_stream(FILE * stream)
+{
+	const int some_pending = (__fpending(stream) != 0);
+	const int prev_fail = (ferror(stream) != 0);
+	const int fclose_fail = (fclose(stream) != 0);
+	if (prev_fail || (fclose_fail && (some_pending || errno != EBADF))) {
+		if (!fclose_fail)
+			errno = 0;
+		return EOF;
+	}
+	return 0;
+}
+
+/* Use atexit(); */
+void close_stdout(void)
+{
+	if (close_stream(stdout) != 0 && !(errno == EPIPE)) {
+		char const *write_error = _("write error");
+		error(0, errno, "%s", write_error);
+		_exit(EXIT_FAILURE);
+	}
+
+	if (close_stream(stderr) != 0)
+		_exit(EXIT_FAILURE);
+}
+
+#ifdef TEST_PROGRAM
+#include <stdio.h>
+int main(int argc, char *argv[])
+{
+	atexit(close_stdout);
+	printf("Hello, World!\n");
+	return EXIT_SUCCESS;
+}
+#endif				/* TEST_PROGRAM */