Exit process if we cannot write to outfile.

This lets process exit when pipe is closed, for instance when piping
output of iperf3 to a script for post processing.

Signed-off-by: Ben Greear <greearb@candelatech.com>

src/iperf_api.c

@@ -4035,31 +4035,41 @@ iperf_printf(struct iperf_test *test, const char* format, ...)
      * easily exceed the size of the line buffer, but which don't need
      * to be buffered up anyway.
      */
+    int rv;
     if (test->role == 'c') {
 	if (test->title)
 	    fprintf(test->outfile, "%s:  ", test->title);
 	va_start(argp, format);
 	r = vfprintf(test->outfile, format, argp);
+        rv = r;
 	va_end(argp);
     }
     else if (test->role == 's') {
 	char linebuffer[1024];
 	va_start(argp, format);
 	r = vsnprintf(linebuffer, sizeof(linebuffer), format, argp);
 	va_end(argp);
-	fprintf(test->outfile, "%s", linebuffer);
+	rv = fprintf(test->outfile, "%s", linebuffer);
 
 	if (test->role == 's' && iperf_get_test_get_server_output(test)) {
 	    struct iperf_textline *l = (struct iperf_textline *) malloc(sizeof(struct iperf_textline));
 	    l->line = strdup(linebuffer);
 	    TAILQ_INSERT_TAIL(&(test->server_output_list), l, textlineentries);
 	}
     }
+
+    if (rv < 0) {
+        /* If printing output fails, go ahead and exit, probably broken pipe */
+        exit(1);
+    }
     return r;
 }
 
 int
 iflush(struct iperf_test *test)
 {
-    return fflush(test->outfile);
+    int rv = fflush(test->outfile);
+    if (rv < 0) {
+        exit(2);
+    }
 }