tail: display file headers correctly with inotify

* src/tail.c (tail_forever_inotify): Use the fspec pointer to
distinguish previously output files, rather than a descriptor
from the inotify event.  That event descriptor was that of
the parent directory when files were created or renamed etc.
(check_fspec): Adjust for the new comparison.  Also show the
header when the file is truncated, since we show data
in this case also.
* tests/tail-2/F-headers.sh: A new test case.
* tests/local.mk: Reference the new test.
* NEWS: Mention the bug fix.

1 files changed, 59 insertions, 0 deletions

diff --git a/tests/tail-2/F-headers.sh b/tests/tail-2/F-headers.sh
new file mode 100755
index 000000000..31d0fa6b1
--- /dev/null
+++ b/tests/tail-2/F-headers.sh
@@ -0,0 +1,59 @@
+#!/bin/sh
+# Ensure tail -F distinguishes output with the correct headers
+# Between coreutils 7.5 and 8.23 inclusive, 'tail -F ...' would
+# not output headers for or created/renamed files in certain cases.
+
+# Copyright (C) 2015 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
+
+check_tail_output()
+{
+  local delay="$1"
+  grep "$tail_re" out ||
+    { sleep $delay; return 1; }
+}
+
+# Terminate any background tail process
+cleanup_() { kill $pid 2>/dev/null && wait $pid; }
+
+# Speedup the non inotify case
+fastpoll='-s.1 --max-unchanged-stats=1'
+
+for mode in '' '---disable-inotify'; do
+  rm -f a b out
+
+  tail $mode -F $fastpoll a b > out 2>&1 & pid=$!
+
+  # Wait up to 12.7s for tail to start.
+  tail_re="cannot open 'b'" retry_delay_ check_tail_output .1 7 ||
+    { cat out; fail=1; }
+
+  echo x > a
+  # Wait up to 12.7s for a's header to appear in the output:
+  tail_re='==> a <==' retry_delay_ check_tail_output .1 7 ||
+    { echo "$0: a: unexpected delay?"; cat out; fail=1; }
+
+  echo y > b
+  # Wait up to 12.7s for b's header to appear in the output:
+  tail_re='==> b <==' retry_delay_ check_tail_output .1 7 ||
+    { echo "$0: b: unexpected delay?"; cat out; fail=1; }
+
+  cleanup_
+done
+
+Exit $fail