tests/tail/symlink.sh

   1 #!/bin/sh
   2 # Ensure tail tracks symlinks properly.
   3
   4 # Copyright (C) 2013-2023 Free Software Foundation, Inc.
   5
   6 # This program is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15
  16 # You should have received a copy of the GNU General Public License
  17 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
  18
  19 . "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
  20 print_ver_ tail
  21
  22 # Function to count number of lines from tail
  23 # while ignoring transient errors due to resource limits
  24 countlines_ ()
  25 {
  26   grep -Ev 'inotify (resources exhausted|cannot be used)' out | wc -l
  27 }
  28
  29 # Function to check the expected line count in 'out'.
  30 # Called via retry_delay_().  Sleep some time - see retry_delay_() - if the
  31 # line count is still smaller than expected.
  32 wait4lines_ ()
  33 {
  34   local delay=$1
  35   local elc=$2   # Expected line count.
  36   [ "$(countlines_)" -ge "$elc" ] || { sleep $delay; return 1; }
  37 }
  38
  39 # Terminate any background tail process
  40 cleanup_() { kill $pid 2>/dev/null && wait $pid; }
  41
  42 # speedup non inotify case
  43 fastpoll='-s.1 --max-unchanged-stats=1'
  44
  45 # Ensure changing targets of cli specified symlinks are handled.
  46 # Prior to v8.22, inotify would fail to recognize changes in the targets.
  47 # Clear 'out' so that we can check its contents without races.
  48 >out                            || framework_failure_
  49 ln -nsf target symlink          || framework_failure_
  50 timeout 10 tail $fastpoll -F symlink >out 2>&1 & pid=$!
  51 # Wait for "cannot open..."
  52 retry_delay_ wait4lines_ .1 6 1 || { cat out; fail=1; }
  53 echo "X" > target               || framework_failure_
  54 # Wait for the expected output.
  55 retry_delay_ wait4lines_ .1 6 3 || { cat out; fail=1; }
  56 cleanup_
  57 # Expect 3 lines in the output file.
  58 [ "$(countlines_)" = 3 ]   || { fail=1; cat out; }
  59 grep -F 'cannot open' out  || { fail=1; cat out; }
  60 grep -F 'has appeared' out || { fail=1; cat out; }
  61 grep '^X$' out             || { fail=1; cat out; }
  62 rm -f target out           || framework_failure_
  63
  64 # Ensure we correctly handle the source symlink itself changing.
  65 # I.e., that we don't operate solely on the targets.
  66 # Clear 'out' so that we can check its contents without races.
  67 >out                            || framework_failure_
  68 echo "X1" > target1             || framework_failure_
  69 ln -nsf target1 symlink         || framework_failure_
  70 timeout 10 tail $fastpoll -F symlink >out 2>&1 & pid=$!
  71 # Wait for the expected output.
  72 retry_delay_ wait4lines_ .1 6 1 || { cat out; fail=1; }
  73 ln -nsf target2 symlink         || framework_failure_
  74 # Wait for "become inaccess..."
  75 retry_delay_ wait4lines_ .1 6 2 || { cat out; fail=1; }
  76 echo "X2" > target2             || framework_failure_
  77 # Wait for the expected output.
  78 retry_delay_ wait4lines_ .1 6 4 || { cat out; fail=1; }
  79 cleanup_
  80 # Expect 4 lines in the output file.
  81 [ "$(countlines_)" = 4 ]    || { fail=1; cat out; }
  82 grep -F 'become inacce' out || { fail=1; cat out; }
  83 grep -F 'has appeared' out  || { fail=1; cat out; }
  84 grep '^X1$' out             || { fail=1; cat out; }
  85 grep '^X2$' out             || { fail=1; cat out; }
  86 rm -f target1 target2 out   || framework_failure_
  87
  88 # Note other symlink edge cases are currently just diagnosed
  89 # rather than being handled.  I.e., if you specify a missing item,
  90 # or existing file that later change to a symlink, if inotify
  91 # is in use, you'll get a diagnostic saying that link will
  92 # no longer be tailed.
  93
  94 Exit $fail