tests: add another sort/nmerge test

* tests/Makefile.am (TESTS): Add sort-merge-fdlimit.
* tests/misc/sort-merge-fdlimit: New file.
* doc/coreutils.texi (sort invocation): Document that we now silently
lower nmerge if necessary.
Patch by Paul Eggert, Nima Nikzad, Max Chang, Alexander Nguyen,
Sahil Amoli, and Nick Graham.

2 files changed, 55 insertions, 0 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index 2fb01c461..3a15a8781 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -204,6 +204,7 @@ TESTS =						\
   misc/sort-continue				\
   misc/sort-files0-from				\
   misc/sort-merge				\
+  misc/sort-merge-fdlimit			\
   misc/sort-rand				\
   misc/sort-version				\
   misc/split-a					\
diff --git a/tests/misc/sort-merge-fdlimit b/tests/misc/sort-merge-fdlimit
new file mode 100755
index 000000000..82305be41
--- /dev/null
+++ b/tests/misc/sort-merge-fdlimit
@@ -0,0 +1,54 @@
+#!/bin/sh
+# Test whether sort avoids opening more file descriptors than it is
+# allowed when merging files.
+
+# Copyright (C) 2009 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/>.
+
+if test "$VERBOSE" = yes; then
+  set -x
+  sort --version
+fi
+
+. $srcdir/test-lib.sh
+require_ulimit_
+
+mkdir in err || framework_failure
+
+fail=0
+
+for i in `seq 17`; do
+  echo $i >in/$i
+done
+
+# When these tests are run inside the automated testing framework, they
+# have one less available file descriptor than when run outside the
+# automated testing framework. If a test with a batch size of b fails
+# inside the ATF, then the same test with batch size b+1 may pass outside
+# the ATF but fail inside it.
+
+# The default batch size (nmerge) is 16.
+(ulimit -n 19 \
+   && sort -m --batch-size=16 in/* 2>err/merge-default-err \
+   || ! grep "open failed" err/merge-default-err) || fail=1
+
+# If sort opens a file (/dev/urandom) to sort by random hashes of keys,
+# it needs to consider this file against its limit on open file
+# descriptors.
+(ulimit -n 20 \
+   && sort -mR --batch-size=16 in/* 2>err/merge-random-err \
+   || ! grep "open failed" err/merge-random-err) || fail=1
+
+Exit $fail