busybox/coreutils/tail.c

320 lines
6.8 KiB
C

/* vi: set sw=4 ts=4: */
/*
* Mini tail implementation for busybox
*
* Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/
/* BB_AUDIT SUSv3 compliant (need fancy for -c) */
/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
/* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
/* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
*
* Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
* Bugs fixed (although I may have forgotten one or two... it was pretty bad)
* 1) mixing printf/write without fflush()ing stdout
* 2) no check that any open files are present
* 3) optstring had -q taking an arg
* 4) no error checking on write in some cases, and a warning even then
* 5) q and s interaction bug
* 6) no check for lseek error
* 7) lseek attempted when count==0 even if arg was +0 (from top)
*/
#include "busybox.h"
static const struct suffix_mult tail_suffixes[] = {
{ "b", 512 },
{ "k", 1024 },
{ "m", 1048576 },
{ NULL, 0 }
};
static int status;
static void tail_xbb_full_write(const char *buf, size_t len)
{
/* If we get a write error, there is really no sense in continuing. */
if (full_write(STDOUT_FILENO, buf, len) < 0)
bb_perror_nomsg_and_die();
}
static void tail_xprint_header(const char *fmt, const char *filename)
{
#if defined __GLIBC__
if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
bb_perror_nomsg_and_die();
}
#else
int hdr_len = strlen(fmt) + strlen(filename);
char *hdr = xzalloc(hdr_len);
sprintf(hdr, filename, filename);
tail_xbb_full_write(hdr, hdr_len);
#endif
}
static ssize_t tail_read(int fd, char *buf, size_t count)
{
ssize_t r;
off_t current,end;
struct stat sbuf;
end = current = lseek(fd, 0, SEEK_CUR);
if (!fstat(fd, &sbuf))
end = sbuf.st_size;
lseek(fd, end < current ? 0 : current, SEEK_SET);
if ((r = safe_read(fd, buf, count)) < 0) {
bb_perror_msg(bb_msg_read_error);
status = EXIT_FAILURE;
}
return r;
}
static const char tail_opts[] =
"fn:c:"
#if ENABLE_FEATURE_FANCY_TAIL
"qs:v"
#endif
;
static const char header_fmt[] = "\n==> %s <==\n";
int tail_main(int argc, char **argv)
{
long count = 10;
unsigned sleep_period = 1;
int from_top = 0;
int follow = 0;
int header_threshhold = 1;
int count_bytes = 0;
char *tailbuf;
size_t tailbufsize;
int taillen = 0;
int newline = 0;
int *fds, nfiles, nread, nwrite, seen, i, opt;
char *s, *buf;
const char *fmt;
#if !ENABLE_DEBUG_YANK_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
/* Allow legacy syntax of an initial numeric option without -n. */
if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
&& isdigit(argv[1][1])
) {
optind = 2;
optarg = argv[1];
goto GET_COUNT;
}
#endif
while ((opt = getopt(argc, argv, tail_opts)) > 0) {
switch (opt) {
case 'f':
follow = 1;
break;
case 'c':
count_bytes = 1;
/* FALLS THROUGH */
case 'n':
#if !ENABLE_DEBUG_YANK_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
GET_COUNT:
#endif
count = xatol_sfx(optarg, tail_suffixes);
/* Note: Leading whitespace is an error trapped above. */
if (*optarg == '+') {
from_top = 1;
} else {
from_top = 0;
}
if (count < 0) {
count = -count;
}
break;
#if ENABLE_FEATURE_FANCY_TAIL
case 'q':
header_threshhold = INT_MAX;
break;
case 's':
sleep_period = xatou(optarg);
break;
case 'v':
header_threshhold = 0;
break;
#endif
default:
bb_show_usage();
}
}
/* open all the files */
fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
argv += optind;
nfiles = i = 0;
if ((argc -= optind) == 0) {
struct stat statbuf;
if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
follow = 0;
}
/* --argv; */
*argv = (char *) bb_msg_standard_input;
goto DO_STDIN;
}
do {
if (LONE_DASH(argv[i])) {
DO_STDIN:
fds[nfiles] = STDIN_FILENO;
} else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
bb_perror_msg("%s", argv[i]);
status = EXIT_FAILURE;
continue;
}
argv[nfiles] = argv[i];
++nfiles;
} while (++i < argc);
if (!nfiles) {
bb_error_msg_and_die("no files");
}
tailbufsize = BUFSIZ;
/* tail the files */
if (from_top < count_bytes) { /* Each is 0 or 1, so true iff 0 < 1. */
/* Hence, !from_top && count_bytes */
if (tailbufsize < count) {
tailbufsize = count + BUFSIZ;
}
}
buf = tailbuf = xmalloc(tailbufsize);
fmt = header_fmt + 1; /* Skip header leading newline on first output. */
i = 0;
do {
/* Be careful. It would be possible to optimize the count-bytes
* case if the file is seekable. If you do though, remember that
* starting file position may not be the beginning of the file.
* Beware of backing up too far. See example in wc.c.
*/
if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
continue;
}
if (nfiles > header_threshhold) {
tail_xprint_header(fmt, argv[i]);
fmt = header_fmt;
}
buf = tailbuf;
taillen = 0;
seen = 1;
newline = 0;
while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
if (from_top) {
nwrite = nread;
if (seen < count) {
if (count_bytes) {
nwrite -= (count - seen);
seen = count;
} else {
s = buf;
do {
--nwrite;
if ((*s++ == '\n') && (++seen == count)) {
break;
}
} while (nwrite);
}
}
tail_xbb_full_write(buf + nread - nwrite, nwrite);
} else if (count) {
if (count_bytes) {
taillen += nread;
if (taillen > count) {
memmove(tailbuf, tailbuf + taillen - count, count);
taillen = count;
}
} else {
int k = nread;
int nbuf = 0;
while (k) {
--k;
if (buf[k] == '\n') {
++nbuf;
}
}
if (newline + nbuf < count) {
newline += nbuf;
taillen += nread;
} else {
int extra = 0;
if (buf[nread-1] != '\n') {
extra = 1;
}
k = newline + nbuf + extra - count;
s = tailbuf;
while (k) {
if (*s == '\n') {
--k;
}
++s;
}
taillen += nread - (s - tailbuf);
memmove(tailbuf, s, taillen);
newline = count - extra;
}
if (tailbufsize < taillen + BUFSIZ) {
tailbufsize = taillen + BUFSIZ;
tailbuf = xrealloc(tailbuf, tailbufsize);
}
}
buf = tailbuf + taillen;
}
}
if (!from_top) {
tail_xbb_full_write(tailbuf, taillen);
}
taillen = 0;
} while (++i < nfiles);
buf = xrealloc(tailbuf, BUFSIZ);
fmt = NULL;
while (follow) {
sleep(sleep_period);
i = 0;
do {
if (nfiles > header_threshhold) {
fmt = header_fmt;
}
while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
if (fmt) {
tail_xprint_header(fmt, argv[i]);
fmt = NULL;
}
tail_xbb_full_write(buf, nread);
}
} while (++i < nfiles);
}
return status;
}