MSVSphere Packaging Team
2 months ago
parent
20d8c199b9
commit
00a1a96898
GPG Key ID:
B2B0B9F29E528FE8
@ -0,0 +1,204 @@
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From 73d119f4f8052a9fb6cef13cd9e75d5a4e23311a Mon Sep 17 00:00:00 2001
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From: dann frazier <dann.frazier@canonical.com>
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Date: Wed, 29 Nov 2023 18:32:34 -0700
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Subject: [PATCH] tail: fix tailing sysfs files where PAGE_SIZE > BUFSIZ
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* src/tail.c (file_lines): Ensure we use a buffer size >= PAGE_SIZE when
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searching backwards to avoid seeking within a file,
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which on sysfs files is accepted but also returns no data.
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* tests/tail/tail-sysfs.sh: Add a new test.
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* tests/local.mk: Reference the new test.
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Fixes https://bugs.gnu.org/67490
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Upstream-commit: 73d119f4f8052a9fb6cef13cd9e75d5a4e23311a
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Cherry-picked-by: Lukáš Zaoral <lzaoral@redhat.com>
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---
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src/tail.c | 57 +++++++++++++++++++++++++++++-----------
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tests/local.mk | 1 +
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tests/tail-2/tail-sysfs.sh | 34 ++++++++++++++++++++++++
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3 files changed, 77 insertions(+), 15 deletions(-)
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create mode 100755 tests/tail/tail-sysfs.sh
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diff --git a/src/tail.c b/src/tail.c
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index c45f3b65a..6979e0ba3 100644
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--- a/src/tail.c
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+++ b/src/tail.c
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@@ -208,6 +208,9 @@ static int nbpids = 0;
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that is writing to all followed files. */
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static pid_t pid;
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+/* Used to determine the buffer size when scanning backwards in a file. */
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+static int page_size;
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+
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/* True if we have ever read standard input. */
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static bool have_read_stdin;
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@@ -515,22 +518,40 @@ xlseek (int fd, off_t offset, int whence, char const *filename)
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Return true if successful. */
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static bool
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-file_lines (const char *pretty_filename, int fd, uintmax_t n_lines,
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- off_t start_pos, off_t end_pos, uintmax_t *read_pos)
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+file_lines (const char *pretty_filename, int fd, struct stat const *sb,
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+ uintmax_t n_lines, off_t start_pos, off_t end_pos,
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+ uintmax_t *read_pos)
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{
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- char buffer[BUFSIZ];
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+ char *buffer;
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size_t bytes_read;
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+ blksize_t bufsize = BUFSIZ;
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off_t pos = end_pos;
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+ bool ok = true;
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if (n_lines == 0)
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return true;
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+ /* Be careful with files with sizes that are a multiple of the page size,
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+ as on /proc or /sys file systems these files accept seeking to within
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+ the file, but then return no data when read. So use a buffer that's
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+ at least PAGE_SIZE to avoid seeking within such files.
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+
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+ We could also indirectly use a large enough buffer through io_blksize()
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+ however this would be less efficient in the common case, as it would
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+ generally pick a larger buffer size, resulting in reading more data
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+ from the end of the file. */
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+ assert (S_ISREG (sb->st_mode));
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+ if (sb->st_size % page_size == 0)
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+ bufsize = MAX (BUFSIZ, page_size);
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+
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+ buffer = xmalloc (bufsize);
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+
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/* Set 'bytes_read' to the size of the last, probably partial, buffer;
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- 0 < 'bytes_read' <= 'BUFSIZ'. */
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- bytes_read = (pos - start_pos) % BUFSIZ;
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+ 0 < 'bytes_read' <= 'bufsize'. */
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+ bytes_read = (pos - start_pos) % bufsize;
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if (bytes_read == 0)
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- bytes_read = BUFSIZ;
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- /* Make 'pos' a multiple of 'BUFSIZ' (0 if the file is short), so that all
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+ bytes_read = bufsize;
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+ /* Make 'pos' a multiple of 'bufsize' (0 if the file is short), so that all
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reads will be on block boundaries, which might increase efficiency. */
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pos -= bytes_read;
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xlseek (fd, pos, SEEK_SET, pretty_filename);
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@@ -538,7 +559,8 @@ file_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
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if (bytes_read == SAFE_READ_ERROR)
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{
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error (0, errno, _("error reading %s"), quoteaf (pretty_filename));
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- return false;
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+ ok = false;
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+ goto free_buffer;
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}
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*read_pos = pos + bytes_read;
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@@ -565,7 +587,7 @@ file_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
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xwrite_stdout (nl + 1, bytes_read - (n + 1));
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*read_pos += dump_remainder (false, pretty_filename, fd,
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end_pos - (pos + bytes_read));
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- return true;
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+ goto free_buffer;
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}
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}
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@@ -577,23 +599,26 @@ file_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
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xlseek (fd, start_pos, SEEK_SET, pretty_filename);
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*read_pos = start_pos + dump_remainder (false, pretty_filename, fd,
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end_pos);
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- return true;
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+ goto free_buffer;
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}
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- pos -= BUFSIZ;
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+ pos -= bufsize;
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xlseek (fd, pos, SEEK_SET, pretty_filename);
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- bytes_read = safe_read (fd, buffer, BUFSIZ);
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+ bytes_read = safe_read (fd, buffer, bufsize);
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if (bytes_read == SAFE_READ_ERROR)
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{
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error (0, errno, _("error reading %s"), quoteaf (pretty_filename));
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- return false;
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+ ok = false;
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+ goto free_buffer;
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}
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*read_pos = pos + bytes_read;
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}
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while (bytes_read > 0);
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- return true;
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+free_buffer:
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+ free (buffer);
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+ return ok;
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}
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/* Print the last N_LINES lines from the end of the standard input,
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@@ -1915,7 +1940,7 @@ tail_lines (char const *pretty_filename, int fd, uintmax_t n_lines,
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{
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*read_pos = end_pos;
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if (end_pos != 0
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- && ! file_lines (pretty_filename, fd, n_lines,
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+ && ! file_lines (pretty_filename, fd, &stats, n_lines,
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start_pos, end_pos, read_pos))
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return false;
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}
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@@ -2337,6 +2362,8 @@ main (int argc, char **argv)
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atexit (close_stdout);
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+ page_size = getpagesize ();
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+
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have_read_stdin = false;
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count_lines = true;
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diff --git a/tests/local.mk b/tests/local.mk
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index db4ee7ed8..bf03238c3 100644
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--- a/tests/local.mk
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+++ b/tests/local.mk
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@@ -257,6 +257,7 @@ all_tests = \
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tests/misc/seq-precision.sh \
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tests/misc/head.pl \
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tests/misc/head-elide-tail.pl \
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+ tests/tail-2/tail-sysfs.sh \
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tests/tail-2/tail-n0f.sh \
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tests/misc/ls-misc.pl \
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tests/misc/date.pl \
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diff --git a/tests/tail/tail-sysfs.sh b/tests/tail-2/tail-sysfs.sh
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new file mode 100755
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index 000000000..00874b3dc
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--- /dev/null
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+++ b/tests/tail-2/tail-sysfs.sh
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@@ -0,0 +1,34 @@
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+#!/bin/sh
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+# sysfs files have weird properties that can be influenced by page size
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+
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+# Copyright 2023 Free Software Foundation, Inc.
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+
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+# This program is free software: you can redistribute it and/or modify
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+# it under the terms of the GNU General Public License as published by
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+# the Free Software Foundation, either version 3 of the License, or
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+# (at your option) any later version.
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+
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+# This program is distributed in the hope that it will be useful,
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+# but WITHOUT ANY WARRANTY; without even the implied warranty of
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+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+# GNU General Public License for more details.
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+
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+# You should have received a copy of the GNU General Public License
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+# along with this program. If not, see <https://www.gnu.org/licenses/>.
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+
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+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
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+print_ver_ tail
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+
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+file='/sys/kernel/profiling'
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+
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+test -r "$file" || skip_ "No $file file"
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+
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+cp -f "$file" exp || framework_failure_
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+
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+tail -n1 "$file" > out || fail=1
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+compare exp out || fail=1
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+
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+tail -c2 "$file" > out || fail=1
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+compare exp out || fail=1
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+
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+Exit $fail
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