df: don't output control characters in a mount point name

It's awkward to read and problematic for scripts when
control characters like '\n' are output.

Note other fields are already handled with mbsalign,
which converts non printable chars to the replacement char.
A caveat to note with that, is the replacement char takes
a place in the field and so possibly truncates the field
if it was the widest field in the records.

Note a more general replacement function, that
handles all printable, or non white space characters,
would require more sophisticated support for various
encodings, and the complexity vs benefit was not
deemed beneficial enough at present.
Perhaps in future a more general replacement function
could be shared between the various utilities.

Note <space> is unaffected in any field,
which could impact scripts processing the output.
However any of the number fields at least could have
spaces considering `LANG=fr_FR df -B\'1`, so it's
probably best to leave spaces, which also allows
scripts to handle mount points with spaces without change.

* src/df.c (hide_problematic_chars): Replace control chars with '?'.
* tests/df/problematic-chars: Add a new root only test.
* tests/Makefile.am: Reference the new test.
* NEWS: Mention the fix.

diff --git a/NEWS b/NEWS
index b8d3cbbbd58b660442f813fc13d07f4e9021d2de..113b30a02093ac6784408033d07d2d640aaa5849 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -13,6 +13,11 @@ GNU coreutils NEWS                                    -*- outline -*-
   date: invalid date '\260'
   [This bug was present in "the beginning".]
 
+  df no longer outputs control characters present in the mount point name.
+  Such characters are replaced with '?', so for example, scripts consuming
+  lines output by df, can work reliably.
+  [This bug was present in "the beginning".]
+
   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

diff --git a/src/df.c b/src/df.c
index 7e30d57f7768b718c64a1d49de2e2a2910cbb4a5..5dc3d2dd0ca72b88e41cea1ba25c3fbff73e4a00 100644 (file)
--- a/src/df.c
+++ b/src/df.c
@@ -192,6 +192,23 @@ static struct option const long_options[] =
   {NULL, 0, NULL, 0}
 };
 
+/* Replace problematic chars with '?'.
+   Since only control characters are currently considered,
+   this should work in all encodings.  */
+
+static char*
+hide_problematic_chars (char *cell)
+{
+  char *p = cell;
+  while (*p)
+    {
+      if (iscntrl (to_uchar (*p)))
+        *p = '?';
+      p++;
+    }
+  return cell;
+}
+
 /* Dynamically allocate a row of pointers in TABLE, which
    can then be accessed with standard 2D array notation.  */
 
@@ -315,6 +332,8 @@ get_header (void)
       if (!cell)
         xalloc_die ();
 
+      hide_problematic_chars (cell);
+
       table[nrows-1][field] = cell;
 
       widths[field] = MAX (widths[field], mbswidth (cell, 0));
@@ -661,7 +680,10 @@ get_dev (char const *disk, char const *mount_point,
         }
 
       if (cell)
-        widths[field] = MAX (widths[field], mbswidth (cell, 0));
+        {
+          hide_problematic_chars (cell);
+          widths[field] = MAX (widths[field], mbswidth (cell, 0));
+        }
       table[nrows-1][field] = cell;
     }
 }

diff --git a/tests/Makefile.am b/tests/Makefile.am
index dfac9a0f3eeca68cc70cc1c5cc71498e68b53eb2..944c7d2e15770a0335da66133582b1d6f2832ebb 100644 (file)
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -31,6 +31,7 @@ root_tests =                                  \
   cp/capability                                        \
   cp/sparse-fiemap                             \
   dd/skip-seek-past-dev                                \
+  df/problematic-chars                         \
   install/install-C-root                       \
   ls/capability                                        \
   ls/nameless-uid                              \

diff --git a/tests/df/problematic-chars b/tests/df/problematic-chars
new file mode 100755 (executable)
index 0000000..801c4d9
--- /dev/null
+++ b/tests/df/problematic-chars
@@ -0,0 +1,44 @@
+#!/bin/sh
+# Ensure that df outputs one line per entry
+
+# 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/>.
+
+. "${srcdir=.}/init.sh"; path_prepend_ ../src
+print_ver_ df
+require_root_
+
+mnt='mount
+point'
+
+cwd=$(pwd)
+cleanup_() { cd /; umount "$cwd/$mnt"; }
+
+skip=0
+# Create a file system, then mount it.
+dd if=/dev/zero of=blob bs=8192 count=200 > /dev/null 2>&1 \
+                                             || skip=1
+mkdir "$mnt"                                 || skip=1
+mkfs -t ext2 -F blob \
+  || skip_ "failed to create ext2 file system"
+
+mount -oloop blob "$mnt"                     || skip=1
+
+test $skip = 1 \
+  && skip_ "insufficient mount/ext2 support"
+
+test $(df "$mnt" | wc -l) = 2 || fail=1
+
+Exit $fail