(NB: we omit the new test, in order to avoid rerunning autoconf.) From 914972e80dbf82aac9ffe3ff1f67f1028e1a788b Mon Sep 17 00:00:00 2001 From: Hannes Braun Date: Wed, 24 Sep 2025 21:20:49 +0200 Subject: [PATCH] tail: fix tailing larger number of lines in regular files * src/tail.c (file_lines): Seek to the previous block instead of the beginning (or a little before) of the block that was just scanned. Otherwise, the same block is read and scanned (at least partially) again. This bug was introduced by commit v9.7-219-g976f8abc1. * tests/tail/basic-seek.sh: Add a new test. * tests/local.mk: Reference the new test. * NEWS: mention the bug fix. --- NEWS | 4 ++++ src/tail.c | 2 +- tests/local.mk | 1 + tests/tail/basic-seek.sh | 28 ++++++++++++++++++++++++++++ 4 files changed, 34 insertions(+), 1 deletion(-) create mode 100755 tests/tail/basic-seek.sh diff --git a/NEWS b/NEWS index 7a1a73113e839f010aa6c734e6f07da68827b953..dc1d26879327761d35499815776477771758edd4 100644 --- a/NEWS +++ b/NEWS @@ -7,6 +7,10 @@ GNU coreutils NEWS -*- outline -*- `basenc --base58` would not operate correctly with input > 15561475 bytes. [bug introduced with --base58 in coreutils-9.8] + 'tail' outputs the correct number of lines again for non-small -n values. + Previously it may have output too few lines. + [bug introduced in coreutils-9.8] + * Noteworthy changes in release 9.8 (2025-09-22) [stable] diff --git a/src/tail.c b/src/tail.c index b8bef1d91cdb6cde2b666b6c1575376e075eaeb8..c7779c77dfe4cf5a672a265b6e796c7153590170 100644 --- a/src/tail.c +++ b/src/tail.c @@ -596,7 +596,7 @@ file_lines (char const *prettyname, int fd, struct stat const *sb, goto free_buffer; } - pos = xlseek (fd, -bufsize, SEEK_CUR, prettyname); + pos = xlseek (fd, -(bufsize + bytes_read), SEEK_CUR, prettyname); bytes_read = read (fd, buffer, bufsize); if (bytes_read < 0) {