wc: line-buffer the printed counts

* src/wc.c (main): Set stdout to line buffered mode
to ensure parallel running instances don't intersperse
their output.  This adds 6.5% to the run time in the worst case
of many zero length files, but has neglible impact for
standard sized files.
* tests/misc/wc-parallel: New test for atomic output.
* tests/Makefile.am: Reference it.
* NEWS: Mention the fix
This is similar to commit 710fe413, 20-10-2009,
"md5sum, sha*sum, sum: line-buffer the printed checksums"

1 files changed, 37 insertions, 0 deletions

diff --git a/tests/misc/wc-parallel b/tests/misc/wc-parallel
new file mode 100755
index 000000000..7c74c5518
--- /dev/null
+++ b/tests/misc/wc-parallel
@@ -0,0 +1,37 @@
+#!/bin/sh
+# Ensure that wc prints counts atomically
+# so that concurrent processes don't intersperse their output
+
+# 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/>.
+
+. $srcdir/test-lib.sh
+
+if test "$VERBOSE" = yes; then
+  set -x
+  md5sum --version
+fi
+
+
+(mkdir tmp && cd tmp && seq 2000 | xargs touch)
+
+# This will output at least 16KiB per process
+# and start 3 processes, with 2 running concurrently,
+# which triggers often on Fedora 11 at least.
+(find tmp tmp tmp -type f | xargs -n2000 -P2 wc) |
+sed -n '/0 0 0 /!p' |
+grep . > /dev/null && fail=1
+
+Exit $fail