1#!/bin/sh
2# Make sure that 'tail -n0 -f' and 'tail -c0 -f' sleep
3# rather than doing what amounted to a busy-wait.
4
5# Copyright (C) 2003-2023 Free Software Foundation, Inc.
6
7# This program is free software: you can redistribute it and/or modify
8# it under the terms of the GNU General Public License as published by
9# the Free Software Foundation, either version 3 of the License, or
10# (at your option) any later version.
11
12# This program is distributed in the hope that it will be useful,
13# but WITHOUT ANY WARRANTY; without even the implied warranty of
14# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15# GNU General Public License for more details.
16
17# You should have received a copy of the GNU General Public License
18# along with this program.  If not, see <https://www.gnu.org/licenses/>.
19
20# This bug was fixed for 5.0.91
21# It skips the test if your system lacks a /proc/$pid/status
22# file, or if its contents don't look right.
23
24. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
25print_ver_ tail
26
27require_proc_pid_status_
28
29touch empty || framework_failure_
30echo anything > nonempty || framework_failure_
31
32# First verify that -[nc]0 without -f, exit without reading
33touch unreadable || framework_failure_
34chmod 0 unreadable || framework_failure_
35tail -c0 unreadable || fail=1
36tail -n0 unreadable || fail=1
37
38# Terminate any background tail process
39cleanup_() { kill $pid 2>/dev/null && wait $pid; }
40
41for mode in '' '---disable-inotify'; do
42  for file in empty nonempty; do
43    for c_or_n in c n; do
44      tail --sleep=4 -${c_or_n} 0 -f $mode $file & pid=$!
45      tail_sleeping()
46      {
47        local delay="$1"; sleep $delay
48        state=$(get_process_status_ $pid)
49        case $state in
50          S*) ;;
51          *) return 1;;
52        esac
53      }
54      # Wait up to 1.5s for tail to sleep
55      retry_delay_ tail_sleeping .1 4 ||
56        { echo $0: process in unexpected state: $state >&2; fail=1; }
57      cleanup_
58    done
59  done
60done
61
62Exit $fail
63