From 1ddcd24d52afbe9af1d7d8712674eed2221cef97 Mon Sep 17 00:00:00 2001
From: Janne Snabb <snabb@epipe.com>
Date: Mon, 6 Feb 2017 23:15:42 -0800
Subject: tail: fix output of redundant headers when resuming

* src/tail.c (check_fspec): Only enable printing of the file header
if we've actually read some data and this is a new file.  Also
move printing of the file header to...
(dump_remainder): ...here, to allow printing only when data read.
* tests/tail-2/overlay-headers.sh: A new test for suspension
and resumption of tail.
* tests/local.mk: Reference the new test.
* NEWS: Mention the fix.
Fixes http://bugs.gnu.org/23539
---
 tests/tail-2/overlay-headers.sh | 81 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100755 tests/tail-2/overlay-headers.sh

(limited to 'tests/tail-2/overlay-headers.sh')

diff --git a/tests/tail-2/overlay-headers.sh b/tests/tail-2/overlay-headers.sh
new file mode 100755
index 000000000..cc4f78968
--- /dev/null
+++ b/tests/tail-2/overlay-headers.sh
@@ -0,0 +1,81 @@
+#!/bin/sh
+# inotify-based tail would output redundant headers for
+# overlapping inotify events while it was suspended
+
+# Copyright (C) 2017 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_ tail sleep
+
+# Function to count number of lines from tail
+# while ignoring transient errors due to resource limits
+countlines_ ()
+{
+  grep -Ev 'inotify (resources exhausted|cannot be used)' out | wc -l
+}
+
+# Function to check the expected line count in 'out'.
+# Called via retry_delay_().  Sleep some time - see retry_delay_() - if the
+# line count is still smaller than expected.
+wait4lines_ ()
+{
+  local delay=$1
+  local elc=$2   # Expected line count.
+  [ "$(countlines_)" -ge "$elc" ] || { sleep $delay; return 1; }
+}
+
+# Speedup the non inotify case
+fastpoll='---dis -s.1 --max-unchanged-stats=1'
+
+# Terminate any background tail process
+cleanup_() {
+  kill $pid 2>/dev/null && wait $pid;
+  kill $sleep 2>/dev/null && wait $sleep
+}
+
+echo start > file1 || framework_failure_
+echo start > file2 || framework_failure_
+
+# Use this as a way to gracefully terminate tail
+env sleep 20 & sleep=$!
+
+tail $fastpoll --pid=$sleep -f file1 file2 > out & pid=$!
+
+kill -0 $pid || fail=1
+
+# Wait for 5 initial lines
+retry_delay_ wait4lines_ .1 6 5 || fail=1
+
+# Suspend tail so single read() caters for multiple inotify events
+kill -STOP $pid || fail=1
+
+# Interleave writes to files to generate overlapping inotify events
+echo line >> file1 || framework_failure_
+echo line >> file2 || framework_failure_
+echo line >> file1 || framework_failure_
+echo line >> file2 || framework_failure_
+
+# Resume tail processing
+kill -CONT $pid || fail=1
+
+# Wait for 8 more lines
+retry_delay_ wait4lines_ .1 6 13 || fail=1
+
+kill $sleep && wait || framework_failure_
+
+test "$(countlines_)" = 13 || fail=1
+
+Exit $fail
-- 
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