df: fix exit code and error messages with --total

When the combination of the file system options with given files or
devices does not lead to output, "df --total" would exit successfully
although it should not.

Examples:
  $ df --total --type=xfs /          # when / is not an XFS file system
  $ df --total --local -t nfs  DIR   # nfs is remote per se ...
  $ df --total -t qwerty /dev/sdb5   # typo in file system type

Furthermore, "df --total" would not print the error message "no file
systems processed" when the file argument does not exist or is otherwise
not accessible.

Example:
  $ df --total __not_exist__

These 2 bugs are present since --total was added by commit
v6.12-166-gea2887b.

* src/df.c (get_dev): Do not set file_systems_processed to true when
force_fsu is true, i.e. when the row for the "total" line is processed.
(main): Don't print totals unless we've processed a file system.
Also only print the "no FS processed" message if there was no
preceding diagnostic.
* tests/df/total-unprocessed: Add a new test.
* tests/Makefile.am: Reference the new test.
* NEWS: Mention the fix.

Improved-by: Jim Meyering

NEWS

@@ -18,6 +18,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   lines output by df, can work reliably.
   [This bug was present in "the beginning".]
 
+  df --total now exits with an appropriate diagnostic and error code, when
+  file system --type options do not lead to a processed file system.
+  [This bug dates back to when --total was added in coreutils-7.0]
+
   head --lines=-N (-n-N) now resets the read pointer of a seekable input file.
   This means that "head -n-3" no longer consumes all of its input, and lines
   not output by head may be processed by other programs.  For example, this

src/df.c

@@ -515,7 +515,8 @@ get_dev (char const *disk, char const *mount_point,
 
   if (! file_systems_processed)
     {
-      file_systems_processed = true;
+      if (! force_fsu)
+        file_systems_processed = true;
       get_header ();
     }
 
@@ -1124,7 +1125,7 @@ main (int argc, char **argv)
   else
     get_all_entries ();
 
-  if (print_grand_total)
+  if (print_grand_total && file_systems_processed)
     {
       if (inode_format)
         grand_fsu.fsu_blocks = 1;
@@ -1133,7 +1134,9 @@ main (int argc, char **argv)
 
   print_table ();
 
-  if (! file_systems_processed)
+  /* Print the "no FS processed" diagnostic only if there was no preceding
+     diagnostic, e.g., if all have been excluded.  */
+  if (exit_status == EXIT_SUCCESS && ! file_systems_processed)
     error (EXIT_FAILURE, 0, _("no file systems processed"));
 
   exit (exit_status);

tests/Makefile.am

@@ -375,6 +375,7 @@ TESTS =						\
   df/header					\
   df/df-P					\
   df/unreadable					\
+  df/total-unprocessed				\
   dd/direct					\
   dd/misc					\
   dd/nocache					\

tests/df/total-unprocessed

@@ -0,0 +1,41 @@
+#!/bin/sh
+# Ensure that df exits non-Zero and writes an error message when
+# --total is used but no file system has been processed.
+
+# Copyright (C) 2012 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+print_ver_ df
+
+cat <<\EOF > exp || framework_failure_
+df: no file systems processed
+EOF
+
+# The following simply finds no match for the combination
+# of the options --local and FS-type nfs together with the
+# argument ".". It must exit non-Zero nonetheless.
+df --local -t nfs --total "." 2>out && fail=1
+compare exp out || fail=1
+
+cat <<\EOF > exp || framework_failure_
+df: '_does_not_exist_': No such file or directory
+EOF
+
+# Ensure that df writes the error message also in the following case.
+df --total _does_not_exist_ 2>out && fail=1
+compare exp out || fail=1
+
+Exit $fail