>From 1f1237ec3201cda16c98611e3c9ebc4541748cac Mon Sep 17 00:00:00 2001 From: Bernhard Voelker Date: Wed, 17 Apr 2013 15:04:48 +0200 Subject: [PATCH 1/2] tail: let -f --retry wait for inaccessible files The --retry option is indeed useful for both following modes by name and by file descriptor. The difference is that in the latter case, it is effective only during the initial open. As a regression of the implementation of the inotify support, tail -f --retry would immediately exit if the given file is inaccessible. * src/tail.c (usage): Change the description of the --retry option: remove the note that this option would mainly be useful when following by name. (main): Change diagnosing dubios uses of --retry option: when the --retry option is used without following, then issue a warning that this option is ignored; when it is used together with --follow=descriptor, then issue a warning that it is only effective for the initial open. Disable inotify also in the case when the initial open in tail_file() failed (which is the actual bug fix). * tests/tail-2/retry.sh: Add new tests. * tests/local.mk (all_tests): Mention it. * doc/coreutils.texi (tail invocation): Enhance the documentation of the --retry option. Clarify the difference in tail's behavior regarding the --retry option when combined with the following modes name versus descriptor. * NEWS (Bug fixes): Mention the fix. Reported by Noel Morrison in: http://lists.gnu.org/archive/html/coreutils/2013-04/msg00003.html --- NEWS | 5 +++ doc/coreutils.texi | 14 ++++++-- src/tail.c | 21 +++++++---- tests/local.mk | 1 + tests/tail-2/retry.sh | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++ 5 files changed, 128 insertions(+), 9 deletions(-) create mode 100644 tests/tail-2/retry.sh diff --git a/NEWS b/NEWS index 0db53d7..fc05b8a 100644 --- a/NEWS +++ b/NEWS @@ -13,6 +13,11 @@ GNU coreutils NEWS -*- outline -*- the relative link on the dereferenced path of an existing link. [This bug was introduced when --relative was added in coreutils-8.16.] + tail --retry -f now waits for the files specified to appear. Before, tail + would immediately exit when such a file is inaccessible during the initial + open. + [This bug was introduced when inotify support was added in coreutils-7.5] + ** New features join accepts a new option: --zero-terminated (-z). As with the sort,uniq diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 92917f1..f6f2eb4 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -3155,9 +3155,17 @@ will keep trying until it becomes accessible again. @item --retry @opindex --retry -This option is useful mainly when following by name (i.e., with -@option{--follow=name}). -Without this option, when tail encounters a file that doesn't +Indefinitely try to open the specified file. +This option is useful mainly when following (and otherwise issues a warning). + +When following by file descriptor (i.e., with @option{--follow=descriptor}), +this option only affects the initial open of the file, as after a successful +open, @command{tail} will start following the file descriptor. + +When following by name (i.e., with @option{--follow=name}), @command{tail} +infinitely retries to re-open the given files until killed. + +Without this option, when @command{tail} encounters a file that doesn't exist or is otherwise inaccessible, it reports that fact and never checks it again. diff --git a/src/tail.c b/src/tail.c index cdaecdd..3735757 100644 --- a/src/tail.c +++ b/src/tail.c @@ -294,9 +294,7 @@ With no FILE, or when FILE is -, read standard input.\n\ fputs (_("\ --pid=PID with -f, terminate after process ID, PID dies\n\ -q, --quiet, --silent never output headers giving file names\n\ - --retry keep trying to open a file even when it is or\n\ - becomes inaccessible; useful when following by\n\ - name, i.e., with --follow=name\n\ + --retry keep trying to open a file if it is inaccessible\n\ "), stdout); fputs (_("\ -s, --sleep-interval=N with -f, sleep for approximately N seconds\n\ @@ -2030,8 +2028,14 @@ parse_options (int argc, char **argv, } } - if (reopen_inaccessible_files && follow_mode != Follow_name) - error (0, 0, _("warning: --retry is useful mainly when following by name")); + if (reopen_inaccessible_files) + { + if (!forever) + error (0, 0, _("warning: --retry ignored; --retry is useful" + " only when following")); + else if (follow_mode == Follow_descriptor) + error (0, 0, _("warning: --retry only effective for the initial open")); + } if (pid && !forever) error (0, 0, @@ -2182,6 +2186,10 @@ main (int argc, char **argv) in this case because it would miss any updates to the file that were not initiated from the local system. + ok is false when one of the files specified could not be opened for + reading. In this case and when following by descriptor, + tail_forever_inotify() cannot be used (in its current implementation). + FIXME: inotify doesn't give any notification when a new (remote) file or directory is mounted on top a watched file. When follow_mode == Follow_name we would ideally like to detect that. @@ -2193,7 +2201,8 @@ main (int argc, char **argv) is recreated, then we don't recheck any new file when follow_mode == Follow_name */ if (!disable_inotify && (tailable_stdin (F, n_files) - || any_remote_file (F, n_files))) + || any_remote_file (F, n_files) + || (!ok && follow_mode == Follow_descriptor))) disable_inotify = true; if (!disable_inotify) diff --git a/tests/local.mk b/tests/local.mk index 0b019d9..f47da8d 100644 --- a/tests/local.mk +++ b/tests/local.mk @@ -390,6 +390,7 @@ all_tests = \ tests/misc/uniq-perf.sh \ tests/misc/xattr.sh \ tests/tail-2/wait.sh \ + tests/tail-2/retry.sh \ tests/chmod/c-option.sh \ tests/chmod/equal-x.sh \ tests/chmod/equals.sh \ diff --git a/tests/tail-2/retry.sh b/tests/tail-2/retry.sh new file mode 100644 index 0000000..dc5218f --- /dev/null +++ b/tests/tail-2/retry.sh @@ -0,0 +1,96 @@ +#!/bin/sh +# Exercise tail's behavior regarding missing files with/without --retry. + +# Copyright (C) 2013 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 . + +. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src +print_ver_ tail + +# Function to wait until a given number of lines appears in 'out', +# but timeout after 5 seconds. +wait4lines_ () +{ + local lc="$1" # expected line count + for i in $( seq 50 ) ; do + [ $( wc -l < out ) -ge "$lc" ] && return 0 + sleep .1 + done + return 1 +} + +# === Test: +# Retry without --follow results in a warning. +touch file +tail --retry file > out 2>&1 || fail=1 +[ $( wc -l < out ) = 1 ] || fail=1 +grep -F 'tail: warning: --retry ignored' out || fail=1 + +# === Test: +# The same with a missing file: expect error message and exit 1. +tail --retry missing > out 2>&1 && fail=1 +[ $( wc -l < out ) = 2 ] || fail=1 +grep -F 'tail: warning: --retry ignored' out || fail=1 + +# === Test: +# Ensure that "tail --retry --follow=name" waits for the file to appear. +timeout 10 tail -s.1 --follow=name --retry missing >out 2>&1 & pid=$! +wait4lines_ 1 || fail=1 # Wait for "cannot open" error. +echo "X" > missing # Create the 'missing' file with some content. +wait4lines_ 3 || fail=1 # Wait for the expected output. +kill $pid +wait $pid +# Expect 3 lines in the output file. +[ $( wc -l < out ) = 3 ] || { fail=1; cat out; } +grep -F 'cannot open' out || { fail=1; cat out; } +grep -F 'has become accessible' out || { fail=1; cat out; } +grep '^X$' out || { fail=1; cat out; } +rm -f missing out || fail=1 + +# === 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 -s.1 --follow=descriptor --retry missing >out 2>&1 & pid=$! +wait4lines_ 2 || fail=1 # Wait for "cannot open" error. +echo "X" > missing # Create the 'missing' file with some content. +wait4lines_ 4 || fail=1 # Wait for the expected output. +kill $pid +wait $pid +# Expect 4 lines in the output file. +[ $( wc -l < out ) = 4 ] || { fail=1; cat out; } +grep -F 'retry only effective for the initial open' out \ + || { fail=1; cat out; } +grep -F 'cannot open' out || { fail=1; cat out; } +grep -F 'has appeared' out || { fail=1; cat out; } +grep '^X$' out || { fail=1; cat out; } +rm -f missing out || fail=1 + +# === 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. +tail --follow=descriptor missing >out 2>&1 && fail=1 +[ $( wc -l < out ) = 2 ] || { fail=1; cat out; } +grep -F 'cannot open' out || { fail=1; cat out; } +grep -F 'no files remaining' out || { fail=1; cat out; } + +# === Test: +# Likewise for --follow=name (without --retry). +tail --follow=name missing >out 2>&1 && fail=1 +[ $( wc -l < out ) = 2 ] || { fail=1; cat out; } +grep -F 'cannot open' out || { fail=1; cat out; } +grep -F 'no files remaining' out || { fail=1; cat out; } + +Exit $fail -- 1.8.1.3.619.g7b6e784 >From 0385077afb24e269eaf8375c6c6bb3524a64095c Mon Sep 17 00:00:00 2001 From: Bernhard Voelker Date: Wed, 17 Apr 2013 15:30:46 +0200 Subject: [PATCH 2/2] tail: exit following by descriptor when no tailable file left As a side effect of the previous commit which fixes 'tail -f --retry' to wait for a file to appear, tail would not exit when the last file appears untailable and gives up on this file. This can happen, for example, when the argument file name appears as directory. Tail sets the 'ignore' flag of this file to true, but instead of exiting the program, tail would continue the loop. * src/tail.c (any_live_files): Change the function to return true if any of the files is still tailable or if tail should continue to try to check again. (tail_forever): Change the condition to break the loop in the "no files remaining" case, because now any_live_files() will care about it, as mentioned above. (parse_options): When --retry is used without any follow mode, then reset reopen_inaccessible_files to false. * tests/tail-2/retry.sh: Add test case. --- src/tail.c | 31 +++++++++++++++++++++++++------ tests/tail-2/retry.sh | 18 ++++++++++++++++++ 2 files changed, 43 insertions(+), 6 deletions(-) diff --git a/src/tail.c b/src/tail.c index 3735757..6bbc725 100644 --- a/src/tail.c +++ b/src/tail.c @@ -1052,16 +1052,32 @@ recheck (struct File_spec *f, bool blocking) } /* Return true if any of the N_FILES files in F are live, i.e., have - open file descriptors. */ + open file descriptors, or should be checked again (see --retry). + When following descriptors, checking should only continue when any + of the files is not yet ignored. */ static bool any_live_files (const struct File_spec *f, size_t n_files) { size_t i; + if (reopen_inaccessible_files && follow_mode == Follow_name) + return true; /* continue following for -F option */ + for (i = 0; i < n_files; i++) - if (0 <= f[i].fd) - return true; + { + if (0 <= f[i].fd) + { + return true; + } + else + { + if (reopen_inaccessible_files && follow_mode == Follow_descriptor) + if (! f[i].ignore) + return true; + } + } + return false; } @@ -1189,7 +1205,7 @@ tail_forever (struct File_spec *f, size_t n_files, double sleep_interval) f[i].size += bytes_read; } - if (! any_live_files (f, n_files) && ! reopen_inaccessible_files) + if (! any_live_files (f, n_files)) { error (0, 0, _("no files remaining")); break; @@ -2031,8 +2047,11 @@ parse_options (int argc, char **argv, if (reopen_inaccessible_files) { if (!forever) - error (0, 0, _("warning: --retry ignored; --retry is useful" - " only when following")); + { + reopen_inaccessible_files = false; + error (0, 0, _("warning: --retry ignored; --retry is useful" + " only when following")); + } else if (follow_mode == Follow_descriptor) error (0, 0, _("warning: --retry only effective for the initial open")); } diff --git a/tests/tail-2/retry.sh b/tests/tail-2/retry.sh index dc5218f..805b93f 100644 --- a/tests/tail-2/retry.sh +++ b/tests/tail-2/retry.sh @@ -78,6 +78,24 @@ grep '^X$' out || { fail=1; cat out; } rm -f missing out || fail=1 # === Test: +# Ensure that tail --follow=descriptor --retry exits when the file appears +# untailable. Expect exit status 1. +timeout 10 tail -s.1 --follow=descriptor --retry missing >out 2>&1 & pid=$! +wait4lines_ 2 || fail=1 # Wait for "cannot open" error. +mkdir missing # Create an untailable 'missing' directory. +wait4lines_ 4 || fail=1 # Wait for the expected output. +wait $pid +rc=$? +[ $( wc -l < out ) = 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 || fail=1 + +# === 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. -- 1.8.1.3.619.g7b6e784