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tail: fix "tail +N file_shorter_than_N"

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2009-08-09 22:06:56 +02:00
parent 0568b6e45a
commit a43df64eec
2 changed files with 27 additions and 6 deletions
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16
coreutils/tail.c
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@ -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;

17
testsuite/tail.tests Executable file
View File

@ -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