df: do not print duplicate entries and rootfs by default

* src/df.c (struct devlist): Add new struct for storing already-
examined device numbers.
(devlist_head): Add new store of the above type.
(show_rootfs): Add new global boolean to not skip rootfs.
(dev_examined): Add new function to check if the device has
already been traversed.
(get_dev): Filter out rootfs unless "-t rootfs" or the -a
option is specified. Filter out duplicate entries by calling
the above new dev_examined unless the -a option is specified.
(main): Set the show_rootfs variable appropriately when the -t
option is specified for rootfs. Free device list (guarded by
IF_LINT).
* tests/df/skip-duplicates.sh: Add test to exercise the skipping
of duplicate entries.
* tests/df/skip-rootfs.sh: Add test to exercise the skipping
of the rootfs pseudo file system.
* tests/local.mk: Add the above new tests.
* NEWS (Changes in behavior): Mention the changes.
* doc/coreutils.texi (df invocation): Document df's behavior about
skipping rootfs and duplicate entries.

Co-authored-by: Bernhard Voelker.

1 files changed, 46 insertions, 0 deletions

diff --git a/tests/df/skip-rootfs.sh b/tests/df/skip-rootfs.sh
new file mode 100755
index 000000000..9ba2716b9
--- /dev/null
+++ b/tests/df/skip-rootfs.sh
@@ -0,0 +1,46 @@
+#!/bin/sh
+# Test df's behavior for skipping the pseudo "rootfs" file system.
+
+# 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=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ df
+
+df || skip_ "df fails"
+
+# Verify that rootfs is in mtab (and shown when the -a option is specified).
+df -a >out || fail=1
+grep '^rootfs' out || skip_ "no rootfs in mtab"
+
+# Ensure that rootfs is supressed when no options is specified.
+df >out || fail=1
+grep '^rootfs' out && { fail=1; cat out; }
+
+# Ensure that the rootfs is shown when explicitly specifying "-t rootfs".
+df -t rootfs >out || fail=1
+grep '^rootfs' out || { fail=1; cat out; }
+
+# Ensure that the rootfs is shown when explicitly specifying "-t rootfs",
+# even when the -a option is specified.
+df -t rootfs -a >out || fail=1
+grep '^rootfs' out || { fail=1; cat out; }
+
+# Ensure that the rootfs is omitted in all_fs mode when it is explicitly
+# black-listed.
+df -a -x rootfs >out || fail=1
+grep '^rootfs' out && { fail=1; cat out; }
+
+Exit $fail