* NEWS: Mention that df exits with nonzero status if it generates

no output.  This change was in 6.0 but inadvertently unmentioned.
* doc/coreutils.texi (df invocation): df exits nonzero if it outpus
nothing.
* src/df.c (file_systems_processed): Renamed from n_valid_args, and now
a boolean.
(show_dev): Don't set it until we actually output something.
Print the header if this is the first output.
(main): Don't print a header, as that is now show_dev's job.
* tests/misc/Makefile.am (TESTS): Add df.
* tests/misc/df: New file.

1 files changed, 10 insertions, 4 deletions

diff --git a/NEWS b/NEWS
index fc9043157..766dfb978 100644
--- a/NEWS
+++ b/NEWS
@@ -59,10 +59,16 @@ GNU coreutils NEWS                                    -*- outline -*-
   date: a command like date -d '2006-04-23 21 days ago' would print
   the wrong date in some time zones.  (see the test for an example)
 
-  df now considers "none" and "proc" file systems to be dummies and
-  therefore does not normally display them.  Also, inaccessible file
-  systems (which can be caused by shadowed mount points or by chrooted
-  bind mounts) are now dummies, too.
+  df changes:
+
+    df now considers "none" and "proc" file systems to be dummies and
+    therefore does not normally display them.  Also, inaccessible file
+    systems (which can be caused by shadowed mount points or by
+    chrooted bind mounts) are now dummies, too.
+
+    df now fails if it generates no output, so you can inspect the
+    exit status of a command like "df -t ext3 -t reiserfs DIR" to test
+    whether DIR is on a file system of type "ext3" or "reiserfs".
 
   expr no longer complains about leading ^ in a regular expression
   (the anchor is ignored), or about regular expressions like A** (the