du: add -t SIZE, --threshold=SIZE option

* src/du.c (opt_threshold): Add variable to hold the value of
the --threshold option specified by the user.
(long_options): Add a required_argument entry for the new
--threshold option.
(usage): Add --threshold option.
(process_file): Elide printing the entry if its size does not
meet the value specified by the --threshold option.
(main): In the argument parsing loop, add a case for the new
-t option. Convert the given argument by permitting the
well-known suffixes for megabyte, gigabytes, etc.
Handle the special case "-0": give an error as this value is
not permitted.
* doc/coreutils.texi (du invocation): Add documentation for the
above new option.
* tests/du/threshold.sh: Add new test to exercise the new option.
* tests/local.mk (all_tests): Mention the above test.

Co-authored-by: Bernhard Voelker <mail@bernhard-voelker.de>

5 files changed, 431 insertions, 3 deletions

diff --git a/NEWS b/NEWS
index 754b2cf89..46d1abafd 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   to include in the output, or all available columns if the FIELD_LIST is
   omitted.  Note this enables df to output both block and inode fields together.
 
+  du now accepts the --threshold=SIZE option to restrict the output to entries
+  with such a minimum SIZE (or a maximum SIZE if it is negative).
+  du recognizes -t SIZE as equivalent, for compatibility with FreeBSD.
+
 ** Bug fixes
 
   cp --no-preserve=mode now no longer exits non-zero.
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 45a4b3d16..8d7eff764 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -11022,6 +11022,41 @@ With @option{--separate-dirs}, the size reported for a directory name,
 @var{d}, is merely the @code{stat.st_size}-derived size of the directory
 entry, @var{d}.
 
+@item -t @var{size}
+@item --threshold=@var{size}
+@opindex -t
+@opindex --threshold
+Exclude entries based on a given @var{size} (@pxref{Block size}).
+
+If @var{size} is positive, then @command{du} will only print entries with a size
+greater than or equal to that.
+
+If @var{size} is negative, then @command{du} will only print entries with a size
+smaller than or equal to that.
+
+Although GNU @command{find} can be used to find files of a certain size,
+@command{du}'s @option{--threshold} option can be used to also filter
+directories based on a given size.
+
+Please note that the @option{--threshold} option can be combined with the
+@option{--apparent-size} option, and in this case would elide entries based on
+its apparent size.
+
+Here's how you would use @option{--threshold} to find directories with a size
+greater than or equal to 200 megabytes:
+
+@example
+du --threshold=200MB
+@end example
+
+Here's how you would use @option{--threshold} to find directories and files -
+note the @option{-a} - with an apparent size smaller than or equal to 500 bytes:
+
+@example
+du -a -t -500 --apparent-size
+@end example
+
+
 @item --time
 @opindex --time
 @cindex last modified dates, displaying in @command{du}
diff --git a/src/du.c b/src/du.c
index 5d8acce58..9b7f8dec5 100644
--- a/src/du.c
+++ b/src/du.c
@@ -147,6 +147,10 @@ static bool opt_separate_dirs = false;
    is at level 0, so 'du --max-depth=0' is equivalent to 'du -s'.  */
 static size_t max_depth = SIZE_MAX;
 
+/* Only output entries with at least this SIZE if positive,
+   or at most if negative.  See --threshold option.  */
+static intmax_t opt_threshold = 0;
+
 /* Human-readable options for output.  */
 static int human_output_opts;
 
@@ -218,6 +222,7 @@ static struct option const long_options[] =
   {"separate-dirs", no_argument, NULL, 'S'},
   {"summarize", no_argument, NULL, 's'},
   {"total", no_argument, NULL, 'c'},
+  {"threshold", required_argument, NULL, 't'},
   {"time", optional_argument, NULL, TIME_OPTION},
   {"time-style", required_argument, NULL, TIME_STYLE_OPTION},
   {GETOPT_HELP_OPTION_DECL},
@@ -319,6 +324,8 @@ Mandatory arguments to long options are mandatory for short options too.\n\
                           only if it is N or fewer levels below the command\n\
                           line argument;  --max-depth=0 is the same as\n\
                           --summarize\n\
+  -t, --threshold=SIZE  exclude entries smaller than SIZE if positive,\n\
+                          or entries greater than SIZE if negative\n\
 "), stdout);
       fputs (_("\
       --time            show time of the last modification of any file in the\n\
@@ -579,8 +586,15 @@ process_file (FTS *fts, FTSENT *ent)
   duinfo_add (&tot_dui, &dui);
 
   if ((IS_DIR_TYPE (info) && level <= max_depth)
-      || ((opt_all && level <= max_depth) || level == 0))
-    print_size (&dui_to_print, file);
+      || (opt_all && level <= max_depth)
+      || level == 0)
+    {
+      /* Print or elide this entry according to the --threshold option.  */
+      if (opt_threshold < 0
+          ? dui_to_print.size <= -opt_threshold
+          : dui_to_print.size >= opt_threshold)
+        print_size (&dui_to_print, file);
+    }
 
   return ok;
 }
@@ -703,7 +717,7 @@ main (int argc, char **argv)
   while (true)
     {
       int oi = -1;
-      int c = getopt_long (argc, argv, "0abd:chHklmsxB:DLPSX:",
+      int c = getopt_long (argc, argv, "0abd:chHklmst:xB:DLPSX:",
                            long_options, &oi);
       if (c == -1)
         break;
@@ -784,6 +798,20 @@ main (int argc, char **argv)
           opt_summarize_only = true;
           break;
 
+        case 't':
+          {
+            enum strtol_error e;
+            e = xstrtoimax (optarg, NULL, 0, &opt_threshold, "kKmMGTPEZY0");
+            if (e != LONGINT_OK)
+              xstrtol_fatal (e, oi, c, long_options, optarg);
+            if (opt_threshold == 0 && *optarg == '-')
+              {
+                /* Do not allow -0, as this wouldn't make sense anyway.  */
+                error (EXIT_FAILURE, 0, _("invalid --threshold argument '-0'"));
+              }
+          }
+          break;
+
         case 'x':
           bit_flags |= FTS_XDEV;
           break;
diff --git a/tests/du/threshold.sh b/tests/du/threshold.sh
new file mode 100644
index 000000000..95e9aedf6
--- /dev/null
+++ b/tests/du/threshold.sh
@@ -0,0 +1,360 @@
+#!/bin/sh
+# Exercise du's --threshold option.
+
+# Copyright (C) 2013 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/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ du
+
+mkdir -p a/b a/c || framework_failure_
+
+touch            a/b/0 || framework_failure_
+printf '%1s' x > a/b/1 || framework_failure_
+printf '%2s' x > a/b/2 || framework_failure_
+printf '%3s' x > a/b/3 || framework_failure_
+
+Ba=$(stat --format="%B * %b" a     | xargs expr)
+Bb=$(stat --format="%B * %b" a/b   | xargs expr)
+Bc=$(stat --format="%B * %b" a/c   | xargs expr)
+B0=$(stat --format="%B * %b" a/b/0 | xargs expr)
+B1=$(stat --format="%B * %b" a/b/1 | xargs expr)
+B2=$(stat --format="%B * %b" a/b/2 | xargs expr)
+B3=$(stat --format="%B * %b" a/b/3 | xargs expr)
+
+Sa=$(stat --format=%s a    )
+Sb=$(stat --format=%s a/b  )
+Sc=$(stat --format=%s a/c  )
+S0=$(stat --format=%s a/b/0)
+S1=$(stat --format=%s a/b/1)
+S2=$(stat --format=%s a/b/2)
+S3=$(stat --format=%s a/b/3)
+
+Bb0123=$(expr $Bb + $B0 + $B1 + $B2 + $B3)
+Sb0123=$(expr $Sb + $S0 + $S1 + $S2 + $S3)
+
+Bab0123=$(expr $Ba + $Bc + $Bb0123)
+Sab0123=$(expr $Sa + $Sc + $Sb0123)
+
+# Sanity checks
+test $Ba -gt 4 || skip_ "block size of a directory is smaller than 4 bytes"
+test $Bc -gt 4 || skip_ "block size of an empty directory is smaller than 4 \
+bytes"
+test $Sa -gt 4 || skip_ "apparent size of a directory is smaller than 4 bytes"
+test $B1 -gt 4 || skip_ "block size of small file smaller than 4 bytes"
+test $S3 -eq 3 || framework_failure_
+test $S2 -eq 2 || framework_failure_
+test $S1 -eq 1 || framework_failure_
+test $S0 -eq 0 || framework_failure_
+test $B0 -eq 0 || skip_ "block size of an empty file unequal Zero"
+# block size of a/b/1 == a/b/2
+test $B1 -eq $B2 || framework_failure_
+# a is bigger than a/b.
+test $Sab0123 -gt $Sb0123 || framework_failure_
+test $Bab0123 -gt $Bb0123 || framework_failure_
+# a/b is bigger than empty a/c.
+test $Sb0123 -gt $Sc || framework_failure_
+test $Bb0123 -gt $Bc || framework_failure_
+
+# Exercise a bad argument: unparsable number.
+cat <<EOF > exp
+du: invalid --threshold argument 'SIZE'
+EOF
+du --threshold=SIZE a > out 2>&1 && fail=1
+compare exp out || fail=1
+
+cat <<EOF > exp
+du: invalid -t argument 'SIZE'
+EOF
+du -t SIZE a > out 2>&1 && fail=1
+compare exp out || fail=1
+
+# Exercise a bad argument: -0 is not valid.
+cat <<EOF > exp
+du: invalid --threshold argument '-0'
+EOF
+du --threshold=-0 a > out 2>&1 && fail=1
+compare exp out || fail=1
+
+du -t -0 a > out 2>&1 && fail=1
+compare exp out || fail=1
+
+du -t-0 a > out 2>&1 && fail=1
+compare exp out || fail=1
+
+# Exercise a bad argument: empty argument.
+cat <<EOF > exp
+du: invalid --threshold argument ''
+EOF
+du --threshold= a > out 2>&1 && fail=1
+compare exp out || fail=1
+
+# Exercise a bad argument: no argument.
+du --threshold > out 2>&1 && fail=1
+cat <<EOF > exp
+du: option '--threshold' requires an argument
+Try 'du --help' for more information.
+EOF
+compare exp out || fail=1
+rm -f out
+
+dutest ()
+{
+  args="$1"
+  exp="$2"
+
+  rm -f exp out
+
+  # Expected output.
+  if [ "$exp" = "" ] ; then
+    touch exp
+  else
+    printf "%s " $exp | tr ' ' "\n" > exp
+  fi
+
+  rc=0
+  du -B1 $args a > out1 2>&1 || { cat out1 ; rc=1 ; }
+
+  # Remove the size column and sort the output.
+  sed 's/^[0-9]*\t//' < out1 | LANG=C sort -o out || framework_failure_
+
+  compare exp out || { cat out1 ; rc=1 ; }
+  return $rc
+}
+
+# Check numbers around the total size of the main directory 'a'.
+# One byte greater than 'a'.
+s=$(expr $Sab0123 + 1)  # apparent size
+dutest "--app       -t $s"  ''                                  || fail=1
+dutest "--app -a    -t $s"  ''                                  || fail=1
+dutest "--app    -S -t $s"  ''                                  || fail=1
+dutest "--app -a -S -t $s"  ''                                  || fail=1
+dutest "--app       -t -$s" 'a a/b a/c'                         || fail=1
+dutest "--app -a    -t -$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+dutest "--app    -S -t -$s" 'a a/b a/c'                         || fail=1
+dutest "--app -a -S -t -$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+s=$(expr $Bab0123 + 1)  # block size
+dutest "            -t $s"  ''                                  || fail=1
+dutest "      -a    -t $s"  ''                                  || fail=1
+dutest "         -S -t $s"  ''                                  || fail=1
+dutest "      -a -S -t $s"  ''                                  || fail=1
+dutest "            -t -$s" 'a a/b a/c'                         || fail=1
+dutest "      -a    -t -$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+dutest "         -S -t -$s" 'a a/b a/c'                         || fail=1
+dutest "      -a -S -t -$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+
+# Exactly the size of 'a'.
+s=$Sab0123  # apparent size
+dutest "--app       --th=$s"  'a'                                 || fail=1
+dutest "--app -a    --th=$s"  'a'                                 || fail=1
+dutest "--app    -S --th=$s"  ''                                  || fail=1
+dutest "--app -a -S --th=$s"  ''                                  || fail=1
+dutest "--app       --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "--app -a    --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+dutest "--app    -S --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "--app -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+s=$Bab0123  # block size
+dutest "            --th=$s"  'a'                                 || fail=1
+dutest "      -a    --th=$s"  'a'                                 || fail=1
+dutest "         -S --th=$s"  ''                                  || fail=1
+dutest "      -a -S --th=$s"  ''                                  || fail=1
+dutest "            --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "      -a    --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+dutest "         -S --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "      -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+
+# One byte smaller than 'a'.
+s=$(expr $Sab0123 - 1)  # apparent size
+dutest "--app       --th=$s"  'a'                                 || fail=1
+dutest "--app -a    --th=$s"  'a'                                 || fail=1
+dutest "--app    -S --th=$s"  ''                                  || fail=1
+dutest "--app -a -S --th=$s"  ''                                  || fail=1
+dutest "--app       --th=-$s" 'a/b a/c'                           || fail=1
+dutest "--app -a    --th=-$s" 'a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'   || fail=1
+dutest "--app    -S --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "--app -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+s=$(expr $Bab0123 - 1)  # block size
+dutest "            --th=$s"  'a'                                 || fail=1
+dutest "      -a    --th=$s"  'a'                                 || fail=1
+dutest "         -S --th=$s"  ''                                  || fail=1
+dutest "      -a -S --th=$s"  ''                                  || fail=1
+dutest "            --th=-$s" 'a/b a/c'                           || fail=1
+dutest "      -a    --th=-$s" 'a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'   || fail=1
+dutest "         -S --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "      -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+
+
+# Check numbers around the total size of the sub directory 'a/b'.
+# One byte greater than 'a/b'.
+s=$(expr $Sb0123 + 1)  # apparent size
+dutest "--app       --th=$s"  'a'                                 || fail=1
+dutest "--app -a    --th=$s"  'a'                                 || fail=1
+dutest "--app    -S --th=$s"  ''                                  || fail=1
+dutest "--app -a -S --th=$s"  ''                                  || fail=1
+dutest "--app       --th=-$s" 'a/b a/c'                           || fail=1
+dutest "--app -a    --th=-$s" 'a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'   || fail=1
+dutest "--app    -S --th=-$s" 'a a/b a/c'                         || fail=1
+dutest "--app -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c' || fail=1
+s=$(expr $Bb0123 + 1)  # block size
+dutest "            --th=$s"  'a'                                  || fail=1
+dutest "      -a    --th=$s"  'a'                                  || fail=1
+dutest "         -S --th=$s"  ''                                   || fail=1
+dutest "      -a -S --th=$s"  ''                                   || fail=1
+dutest "            --th=-$s" 'a/b a/c'                            || fail=1
+dutest "      -a    --th=-$s" 'a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'    || fail=1
+dutest "         -S --th=-$s" 'a a/b a/c'                          || fail=1
+dutest "      -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+
+# Exactly the size of 'a/b'.
+s=$Sb0123  # apparent size
+dutest "--app       --th=$s"  'a a/b'                              || fail=1
+dutest "--app -a    --th=$s"  'a a/b'                              || fail=1
+dutest "--app    -S --th=$s"  'a/b'                                || fail=1
+dutest "--app -a -S --th=$s"  'a/b'                                || fail=1
+dutest "--app       --th=-$s" 'a/b a/c'                            || fail=1
+dutest "--app -a    --th=-$s" 'a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'    || fail=1
+dutest "--app    -S --th=-$s" 'a a/b a/c'                          || fail=1
+dutest "--app -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+s=$Bb0123  # block size
+dutest "            --th=$s"  'a a/b'                              || fail=1
+dutest "      -a    --th=$s"  'a a/b'                              || fail=1
+dutest "         -S --th=$s"  'a/b'                                || fail=1
+dutest "      -a -S --th=$s"  'a/b'                                || fail=1
+dutest "            --th=-$s" 'a/b a/c'                            || fail=1
+dutest "      -a    --th=-$s" 'a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'    || fail=1
+dutest "         -S --th=-$s" 'a a/b a/c'                          || fail=1
+dutest "      -a -S --th=-$s" 'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+
+# One byte smaller than 'a/b'.
+s=$(expr $Sb0123 - 1)  # apparent size
+dutest "--app       --th=$s"  'a a/b'                              || fail=1
+dutest "--app -a    --th=$s"  'a a/b'                              || fail=1
+dutest "--app    -S --th=$s"  'a/b'                                || fail=1
+dutest "--app -a -S --th=$s"  'a/b'                                || fail=1
+dutest "--app       --th=-$s" 'a/c'                                || fail=1
+dutest "--app -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "--app    -S --th=-$s" 'a a/c'                              || fail=1
+dutest "--app -a -S --th=-$s" 'a a/b/0 a/b/1 a/b/2 a/b/3 a/c'      || fail=1
+s=$(expr $Bb0123 - 1)  # block size
+dutest "            --th=$s"  'a a/b'                              || fail=1
+dutest "      -a    --th=$s"  'a a/b'                              || fail=1
+dutest "         -S --th=$s"  'a/b'                                || fail=1
+dutest "      -a -S --th=$s"  'a/b'                                || fail=1
+dutest "            --th=-$s" 'a/c'                                || fail=1
+dutest "      -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=-$s" 'a a/c'                              || fail=1
+dutest "      -a -S --th=-$s" 'a a/b/0 a/b/1 a/b/2 a/b/3 a/c'      || fail=1
+
+
+# Check numbers around the total size of the files a/b/[0123]'.
+echo One byte greater than 'a/b/3'.
+s=$(expr $S3 + 1)  # apparent size
+dutest "--app       --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a    --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app    -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app       --th=-$s" ''                                   || fail=1
+dutest "--app -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3'            || fail=1
+dutest "--app    -S --th=-$s" ''                                   || fail=1
+dutest "--app -a -S --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3'            || fail=1
+s=$(expr $B3 + 1)  # block size
+dutest "            --th=$s"  'a a/b'                              || fail=1
+dutest "      -a    --th=$s"  'a a/b'                              || fail=1
+dutest "         -S --th=$s"  'a/b'                                || fail=1
+dutest "      -a -S --th=$s"  'a/b'                                || fail=1
+dutest "            --th=-$s" 'a/c'                                || fail=1
+dutest "      -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=-$s" 'a a/c'                              || fail=1
+dutest "      -a -S --th=-$s" 'a a/b/0 a/b/1 a/b/2 a/b/3 a/c'      || fail=1
+
+# Exactly the size of 'a/b/3'.
+echo Exactly the size of 'a/b/3'.
+s=$S3  # apparent size
+dutest "--app       --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a    --th=$s"  'a a/b a/b/3 a/c'                    || fail=1
+dutest "--app    -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a -S --th=$s"  'a a/b a/b/3 a/c'                    || fail=1
+dutest "--app       --th=-$s" ''                                   || fail=1
+dutest "--app -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3'            || fail=1
+dutest "--app    -S --th=-$s" ''                                   || fail=1
+dutest "--app -a -S --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3'            || fail=1
+s=$B3  # block size
+dutest "            --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a    --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a -S --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "            --th=-$s" 'a/c'                                || fail=1
+dutest "      -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=-$s" 'a a/c'                              || fail=1
+dutest "      -a -S --th=-$s" 'a a/b/0 a/b/1 a/b/2 a/b/3 a/c'      || fail=1
+
+# Exactly the size of 'a/b/2'.
+echo Exactly the size of 'a/b/2'.
+s=$S2  # apparent size
+dutest "--app       --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a    --th=$s"  'a a/b a/b/2 a/b/3 a/c'              || fail=1
+dutest "--app    -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a -S --th=$s"  'a a/b a/b/2 a/b/3 a/c'              || fail=1
+dutest "--app       --th=-$s" ''                                   || fail=1
+dutest "--app -a    --th=-$s" 'a/b/0 a/b/1 a/b/2'                  || fail=1
+dutest "--app    -S --th=-$s" ''                                   || fail=1
+dutest "--app -a -S --th=-$s" 'a/b/0 a/b/1 a/b/2'                  || fail=1
+s=$B2  # block size
+dutest "            --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a    --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a -S --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "            --th=-$s" 'a/c'                                || fail=1
+dutest "      -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=-$s" 'a a/c'                              || fail=1
+dutest "      -a -S --th=-$s" 'a a/b/0 a/b/1 a/b/2 a/b/3 a/c'      || fail=1
+
+# Exactly the size of 'a/b/1'.
+echo Exactly the size of 'a/b/1'.
+s=$S1  # apparent size
+dutest "--app       --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a    --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "--app    -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a -S --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "--app       --th=-$s" ''                                   || fail=1
+dutest "--app -a    --th=-$s" 'a/b/0 a/b/1'                        || fail=1
+dutest "--app    -S --th=-$s" ''                                   || fail=1
+dutest "--app -a -S --th=-$s" 'a/b/0 a/b/1'                        || fail=1
+s=$B1  # block size
+dutest "            --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a    --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a -S --th=$s"  'a a/b a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "            --th=-$s" 'a/c'                                || fail=1
+dutest "      -a    --th=-$s" 'a/b/0 a/b/1 a/b/2 a/b/3 a/c'        || fail=1
+dutest "         -S --th=-$s" 'a a/c'                              || fail=1
+dutest "      -a -S --th=-$s" 'a a/b/0 a/b/1 a/b/2 a/b/3 a/c'      || fail=1
+
+# Exactly the size of 'a/b/0'.
+echo Exactly the size of 'a/b/0'.
+s=$S0  # apparent size
+dutest "--app       --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a    --th=$s"  'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+dutest "--app    -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "--app -a -S --th=$s"  'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+# (maximum tests (-0) not possible).
+s=$B0  # block size
+dutest "            --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a    --th=$s"  'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+dutest "         -S --th=$s"  'a a/b a/c'                          || fail=1
+dutest "      -a -S --th=$s"  'a a/b a/b/0 a/b/1 a/b/2 a/b/3 a/c'  || fail=1
+# (maximum tests (-0) not possible).
+
+Exit $fail
diff --git a/tests/local.mk b/tests/local.mk
index 02d1c087c..82daee5cd 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -497,6 +497,7 @@ all_tests =					\
   tests/du/one-file-system.sh			\
   tests/du/restore-wd.sh			\
   tests/du/slash.sh				\
+  tests/du/threshold.sh				\
   tests/du/trailing-slash.sh			\
   tests/du/two-args.sh				\
   tests/id/gnu-zero-uids.sh			\