From 69ca5a70fd4ae30f8a3beabec4d705f7dd32e3f3 Mon Sep 17 00:00:00 2001
From: Denis Vlasenko <vda.linux@googlemail.com>
Date: Sun, 23 Mar 2008 03:28:40 +0000
Subject: [PATCH] tail: fix fallout from tail -c optimization

---
 coreutils/tail.c            | 22 +++++++++-------------
 testsuite/tail/tail-n-works |  8 ++++----
 testsuite/tail/tail-works   |  8 ++++----
 3 files changed, 17 insertions(+), 21 deletions(-)

diff --git a/coreutils/tail.c b/coreutils/tail.c
index 35b25a416..2f997a9f6 100644
--- a/coreutils/tail.c
+++ b/coreutils/tail.c
@@ -163,8 +163,6 @@ int tail_main(int argc, char **argv)
 	fmt = header_fmt + 1;	/* Skip header leading newline on first output. */
 	i = 0;
 	do {
-		off_t current;
-
 		if (nfiles > header_threshhold) {
 			tail_xprint_header(fmt, argv[i]);
 			fmt = header_fmt;
@@ -173,19 +171,17 @@ int tail_main(int argc, char **argv)
 		/* Optimizing count-bytes case if the file is seekable.
 		 * Beware of backing up too far.
 		 * Also we exclude files with size 0 (because of /proc/xxx) */
-		current = lseek(fds[i], 0, SEEK_END);
-		if (current > 0) {
-			if (!from_top) {
+		if (COUNT_BYTES && !from_top) {
+			off_t current = lseek(fds[i], 0, SEEK_END);
+			if (current > 0) {
 				if (count == 0)
 					continue; /* showing zero lines is easy :) */
-				if (COUNT_BYTES) {
-					current -= count;
-					if (current < 0)
-						current = 0;
-					xlseek(fds[i], current, SEEK_SET);
-					bb_copyfd_size(fds[i], STDOUT_FILENO, count);
-					continue;
-				}
+				current -= count;
+				if (current < 0)
+					current = 0;
+				xlseek(fds[i], current, SEEK_SET);
+				bb_copyfd_size(fds[i], STDOUT_FILENO, count);
+				continue;
 			}
 		}
 
diff --git a/testsuite/tail/tail-n-works b/testsuite/tail/tail-n-works
index 27a905f88..e5b260caf 100644
--- a/testsuite/tail/tail-n-works
+++ b/testsuite/tail/tail-n-works
@@ -1,4 +1,4 @@
-[ -n "$d" ] || d=..
-tail -n 2 "$d/README" > logfile.gnu
-busybox tail -n 2 "$d/README" > logfile.bb
-cmp logfile.gnu logfile.bb
+echo -ne "abc\ndef\n123\n" >input
+echo -ne "def\n123\n" >logfile.ok
+busybox tail -n 2 input > logfile.bb
+cmp logfile.ok logfile.bb
diff --git a/testsuite/tail/tail-works b/testsuite/tail/tail-works
index 27a905f88..64e6d88ab 100644
--- a/testsuite/tail/tail-works
+++ b/testsuite/tail/tail-works
@@ -1,4 +1,4 @@
-[ -n "$d" ] || d=..
-tail -n 2 "$d/README" > logfile.gnu
-busybox tail -n 2 "$d/README" > logfile.bb
-cmp logfile.gnu logfile.bb
+echo -ne "abc\ndef\n123\n" >input
+echo -ne "def\n123\n" >logfile.ok
+busybox tail -2 input > logfile.bb
+cmp logfile.ok logfile.bb