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#!/bin/sh
# Exercise tail's behavior regarding missing files with/without --retry.
# Copyright (C) 2013-2026 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 <https://www.gnu.org/licenses/>.
. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
print_ver_ tail
# 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; }
}
# Terminate any background tail process
cleanup_() { kill $pid 2>/dev/null && wait $pid; }
# Speedup the non inotify case
fastpoll='-s.1 --max-unchanged-stats=1'
# === Test:
# Retry without --follow results in a warning.
touch file
tail --retry file > out 2>&1 || fail=1
[ "$(countlines_)" = 1 ] || { cat out; fail=1; }
grep -F 'tail: warning: --retry ignored' out || { cat out; fail=1; }
# === Test:
# The same with a missing file: expect error message and exit 1.
returns_ 1 tail --retry missing > out 2>&1 || fail=1
[ "$(countlines_)" = 2 ] || { cat out; fail=1; }
grep -F 'tail: warning: --retry ignored' out || { cat out; fail=1; }
for mode in '' '---disable-inotify'; do
# === Test:
# Ensure that "tail --retry --follow=name" waits for the file to appear.
# Clear 'out' so that we can check its contents without races
>out || framework_failure_
timeout 10 \
tail $mode $fastpoll --follow=name --retry missing >out 2>&1 & pid=$!
# Wait for "cannot open" error.
retry_delay_ wait4lines_ .1 6 1 || { cat out; fail=1; }
echo "X" > missing || framework_failure_
# Wait for the expected output.
retry_delay_ wait4lines_ .1 6 3 || { cat out; fail=1; }
cleanup_
# Expect 3 lines in the output file.
[ "$(countlines_)" = 3 ] || { fail=1; cat out; }
grep -F 'cannot open' out || { fail=1; cat out; }
grep -F 'has appeared' out || { fail=1; cat out; }
grep '^X$' out || { fail=1; cat out; }
rm -f missing out || framework_failure_
# === Test:
# Ensure that "tail --retry --follow=descriptor" waits for the file to appear.
# tail-8.21 failed at this (since the implementation of the inotify support).
timeout 10 \
tail $mode $fastpoll --follow=descriptor --retry missing >out 2>&1 & pid=$!
# Wait for "cannot open" error.
retry_delay_ wait4lines_ .1 6 2 || { cat out; fail=1; }
echo "X1" > missing || framework_failure_
# Wait for the expected output.
retry_delay_ wait4lines_ .1 6 4 || { cat out; fail=1; }
# Ensure truncation is detected
# tail-8.25 failed at this (as assumed non file and went into blocking mode)
echo "X" > missing || framework_failure_
retry_delay_ wait4lines_ .1 6 6 || { cat out; fail=1; }
cleanup_
[ "$(countlines_)" = 6 ] || { fail=1; cat out; }
grep -F 'retry only effective for the initial open' out \
|| { fail=1; cat out; }
grep -F 'cannot open' out || { fail=1; cat out; }
grep -F 'has appeared' out || { fail=1; cat out; }
grep '^X1$' out || { fail=1; cat out; }
grep -F 'file truncated' out || { fail=1; cat out; }
grep '^X$' out || { fail=1; cat out; }
rm -f missing out || framework_failure_
# === Test:
# Ensure that tail --follow=descriptor --retry exits when the file appears
# untailable. Expect exit status 1.
timeout 10 \
tail $mode $fastpoll --follow=descriptor --retry missing >out 2>&1 & pid=$!
# Wait for "cannot open" error.
retry_delay_ wait4lines_ .1 6 2 || { cat out; fail=1; }
mkdir missing || framework_failure_ # Create untailable
# Wait for the expected output.
retry_delay_ wait4lines_ .1 6 4 || { cat out; fail=1; }
wait $pid
rc=$?
[ "$(countlines_)" = 4 ] || { fail=1; cat out; }
grep -F 'retry only effective for the initial open' out \
|| { fail=1; cat out; }
grep -F 'cannot open' out || { fail=1; cat out; }
grep -F 'replaced with an untailable file' out || { fail=1; cat out; }
grep -F 'no files remaining' out || { fail=1; cat out; }
[ $rc = 1 ] || { fail=1; cat out; }
rm -fd missing out || framework_failure_
# === Test:
# Ensure that --follow=descriptor (without --retry) does *not* try
# to open a file after an initial fail, even when there are other
# tailable files. This was an issue in <= 8.25.
touch existing || framework_failure_
tail $mode $fastpoll --follow=descriptor missing existing >out 2>&1 & pid=$!
retry_delay_ wait4lines_ .1 6 2 || { cat out; fail=1; }
[ "$(countlines_)" = 2 ] || { fail=1; cat out; }
grep -F 'cannot open' out || { fail=1; cat out; }
echo "Y" > missing || framework_failure_
echo "X" > existing || framework_failure_
retry_delay_ wait4lines_ .1 6 3 || { cat out; fail=1; }
[ "$(countlines_)" = 3 ] || { fail=1; cat out; }
grep '^X$' out || { fail=1; cat out; }
grep '^Y$' out && { fail=1; cat out; }
cleanup_
rm -f missing out existing || framework_failure_
# === Test:
# Ensure that --follow=descriptor (without --retry) does *not wait* for the
# file to appear. Expect 2 lines in the output file ("cannot open" +
# "no files remaining") and exit status 1.
returns_ 1 tail $mode --follow=descriptor missing >out 2>&1 || fail=1
[ "$(countlines_)" = 2 ] || { fail=1; cat out; }
grep -F 'cannot open' out || { fail=1; cat out; }
grep -F 'no files remaining' out || { fail=1; cat out; }
rm -f out || framework_failure_
# === Test:
# Likewise for --follow=name (without --retry).
returns_ 1 tail $mode --follow=name missing >out 2>&1 || fail=1
[ "$(countlines_)" = 2 ] || { fail=1; cat out; }
grep -F 'cannot open' out || { fail=1; cat out; }
grep -F 'no files remaining' out || { fail=1; cat out; }
rm -f out || framework_failure_
# === Test:
# Ensure that tail -F retries when the file is initially untailable.
if ! cat . >/dev/null; then
mkdir untailable || framework_failure_
timeout 10 \
tail $mode $fastpoll -F untailable >out 2>&1 & pid=$!
# Wait for "cannot follow" error.
retry_delay_ wait4lines_ .1 6 2 || { cat out; fail=1; }
{ rmdir untailable; echo foo > untailable; } || framework_failure_
# Wait for the expected output.
retry_delay_ wait4lines_ .1 6 4 || { cat out; fail=1; }
cleanup_
[ "$(countlines_)" = 4 ] || { fail=1; cat out; }
grep -F 'cannot follow' out || { fail=1; cat out; }
# The first is the common case, "has appeared" arises with slow rmdir.
grep -E 'become accessible|has appeared' out || { fail=1; cat out; }
grep -F 'giving up' out && { fail=1; cat out; }
grep -F 'foo' out || { fail=1; cat out; }
rm -fd untailable out || framework_failure_
fi
done
Exit $fail
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