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authorDenys Vlasenko2009-08-09 22:06:56 +0200
committerDenys Vlasenko2009-08-09 22:06:56 +0200
commita43df64eec6d02812b40d7e01edbeb47539866db (patch)
tree591a7f6a995901fbbc8d4f893c48b565d6cac888
parent0568b6e45aa59c72815378134715232fd11d9100 (diff)
downloadbusybox-a43df64eec6d02812b40d7e01edbeb47539866db.zip
busybox-a43df64eec6d02812b40d7e01edbeb47539866db.tar.gz
tail: fix "tail +N file_shorter_than_N"
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--coreutils/tail.c16
-rwxr-xr-xtestsuite/tail.tests17
2 files changed, 27 insertions, 6 deletions
diff --git a/coreutils/tail.c b/coreutils/tail.c
index ef1326c..5f98bff 100644
--- a/coreutils/tail.c
+++ b/coreutils/tail.c
@@ -50,12 +50,12 @@ static ssize_t tail_read(int fd, char *buf, size_t count)
off_t current;
struct stat sbuf;
- /* (A good comment is missing here) */
- current = lseek(fd, 0, SEEK_CUR);
/* /proc files report zero st_size, don't lseek them. */
- if (fstat(fd, &sbuf) == 0 && sbuf.st_size)
+ if (fstat(fd, &sbuf) == 0 && sbuf.st_size) {
+ current = lseek(fd, 0, SEEK_CUR);
if (sbuf.st_size < current)
lseek(fd, 0, SEEK_SET);
+ }
r = full_read(fd, buf, count);
if (r < 0) {
@@ -119,10 +119,11 @@ int tail_main(int argc, char **argv)
#if ENABLE_FEATURE_FANCY_TAIL
/* q: make it impossible for nfiles to be > header_threshhold */
if (opt & 0x8) header_threshhold = UINT_MAX; // -q
+ //if (opt & 0x10) // -s
if (opt & 0x20) header_threshhold = 0; // -v
-#define FOLLOW_RETRY (opt & 0x40)
+# define FOLLOW_RETRY (opt & 0x40)
#else
-#define FOLLOW_RETRY 0
+# define FOLLOW_RETRY 0
#endif
argc -= optind;
argv += optind;
@@ -189,7 +190,7 @@ int tail_main(int argc, char **argv)
off_t current = lseek(fds[i], 0, SEEK_END);
if (current > 0) {
if (count == 0)
- continue; /* showing zero lines is easy :) */
+ continue; /* showing zero bytes is easy :) */
current -= count;
if (current < 0)
current = 0;
@@ -201,12 +202,15 @@ int tail_main(int argc, char **argv)
buf = tailbuf;
taillen = 0;
+ /* "We saw 1st line/byte".
+ * Used only by +N code ("start from Nth", 1-based) */
seen = 1;
newlines_seen = 0;
while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
if (from_top) {
int nwrite = nread;
if (seen < count) {
+ /* We need to skip a few more bytes/lines */
if (COUNT_BYTES) {
nwrite -= (count - seen);
seen = count;
diff --git a/testsuite/tail.tests b/testsuite/tail.tests
new file mode 100755
index 0000000..d97bf7b
--- /dev/null
+++ b/testsuite/tail.tests
@@ -0,0 +1,17 @@
+#!/bin/sh
+
+# Copyright 2009 by Denys Vlasenko <vda.linux@googlemail.com>
+# Licensed under GPL v2, see file LICENSE for details.
+
+. testing.sh
+
+# testing "test name" "command" "expected result" "file input" "stdin"
+# file input will be file called "input"
+# test can create a file "actual" instead of writing to stdout
+
+testing "tail: +N with N > file length" \
+ "tail -c +55 2>&1; echo \$?" \
+ "0\n" \
+ "" "qw"
+
+exit $FAILCOUNT