6623 iostat -exrn has missing comma (field separator) in header
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>

@@ -27,10 +27,11 @@
  * rewritten from SunOS 4.1 SID 1.18 89/10/06
  */
 /*
  * Copyright (c) 2012 by Delphix. All rights reserved.
  * Copyright 2015 Nexenta Systems, Inc. All rights reserved.
+ * Copyright 2016 James S. Blachly, MD. All rights reserved.
  */
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>

@@ -1268,11 +1269,11 @@
  */
 
 void
 do_format(void)
 {
-        char    header[SMALL_SCRATCH_BUFLEN];
+        char    header[SMALL_SCRATCH_BUFLEN] = {0};
         char    ch;
         char    iosz;
         const char    *fstr;
 
         disk_header[0] = 0;

@@ -1281,12 +1282,11 @@
         if (do_disk & DISK_ERRORS) {
                 if (do_raw == 0) {
                         (void) sprintf(header, "s/w h/w trn tot ");
                 } else
                         (void) sprintf(header, "s/w,h/w,trn,tot");
-        } else
-                *header = NULL;
+        }
         switch (do_disk & DISK_IO_MASK) {
                 case DISK_OLD:
                         if (do_raw == 0)
                                 fstr = "%cp%c tp%c serv  ";
                         else

@@ -1319,12 +1319,19 @@
                                         /* with -r option */
                                         (void) snprintf(disk_header,
                                             sizeof (disk_header),
                                             "device,r/%c,w/%c,%cr/%c,%cw/%c,"
                                             "wait,actv,svc_t,%%%%w,"
-                                            "%%%%b,%s",
-                                            ch, ch, iosz, ch, iosz, ch, header);
+                                            "%%%%b%s%s",
+                                            ch, ch, iosz, ch, iosz, ch,
+                                            *header == '\0' ? "" : ",",
+                                            header);
+                                        /*
+                                         * if no -e flag, header == '\0...'
+                                         * Ternary operator above is to prevent
+                                         * trailing comma in full disk_header
+                                         */
                                 }
                         } else {
                                 /* with -n option */
                                 if (do_raw == 0) {
                                         fstr = "    r/%c    w/%c   %cr/%c   "

@@ -1332,10 +1339,22 @@
                                             "%%%%w  %%%%b %sdevice";
                                 } else {
                                         fstr = "r/%c,w/%c,%cr/%c,%cw/%c,"
                                             "wait,actv,wsvc_t,asvc_t,"
                                             "%%%%w,%%%%b,%sdevice";
+                                        /*
+                                         * if -rnxe, "tot" (from -e) and
+                                         * "device" are run together
+                                         * due to lack of trailing comma
+                                         * in 'header'. However, adding
+                                         * trailing comma to header at
+                                         * its definition leads to prob-
+                                         * lems elsewhere so it's added
+                                         * here in this edge case -rnxe
+                                         */
+                                        if (*header != '\0')
+                                                (void) strcat(header, ",");
                                 }
                                 (void) snprintf(disk_header,
                                     sizeof (disk_header),
                                     fstr, ch, ch, iosz, ch, iosz,
                                     ch, header);