* 7) lseek attempted when count==0 even if arg was +0 (from top)
*/
-#include "busybox.h"
+#include "libbb.h"
static const struct suffix_mult tail_suffixes[] = {
{ "b", 512 },
{ "k", 1024 },
{ "m", 1024*1024 },
- { NULL, 0 }
+ { "", 0 }
};
-static int status;
+struct globals {
+ bool status;
+};
+#define G (*(struct globals*)&bb_common_bufsiz1)
static void tail_xprint_header(const char *fmt, const char *filename)
{
static ssize_t tail_read(int fd, char *buf, size_t count)
{
ssize_t r;
- off_t current, end;
+ off_t current;
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);
- r = safe_read(fd, buf, count);
+ /* /proc files report zero st_size, don't lseek them. */
+ if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
+ current = lseek(fd, 0, SEEK_CUR);
+ if (sbuf.st_size < current)
+ xlseek(fd, 0, SEEK_SET);
+ }
+
+ r = full_read(fd, buf, count);
if (r < 0) {
bb_perror_msg(bb_msg_read_error);
- status = EXIT_FAILURE;
+ G.status = EXIT_FAILURE;
}
return r;
}
-static const char header_fmt[] = "\n==> %s <==\n";
+static const char header_fmt[] ALIGN1 = "\n==> %s <==\n";
-static unsigned eat_num(const char *p) {
- if (*p == '-') p++;
- else if (*p == '+') { p++; status = 1; }
+static unsigned eat_num(const char *p)
+{
+ if (*p == '-')
+ p++;
+ else if (*p == '+') {
+ p++;
+ G.status = 1; /* mark that we saw "+" */
+ }
return xatou_sfx(p, tail_suffixes);
}
+int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int tail_main(int argc, char **argv)
{
unsigned count = 10;
unsigned sleep_period = 1;
bool from_top;
- int header_threshhold = 1;
- const char *str_c, *str_n, *str_s;
+ const char *str_c, *str_n;
char *tailbuf;
size_t tailbufsize;
- int taillen = 0;
- int newline = 0;
- int nfiles, nread, nwrite, seen, i, opt;
+ unsigned header_threshhold = 1;
+ unsigned nfiles;
+ int i, opt;
int *fds;
- char *s, *buf;
const char *fmt;
#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
/* Allow legacy syntax of an initial numeric option without -n. */
- if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
+ if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-')
&& isdigit(argv[1][1])
) {
- argv[0] = (char*)"-n";
- argv--;
- argc++;
+ count = eat_num(argv[1]);
+ argv++;
+ argc--;
}
#endif
- opt = getopt32(argc, argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"), &str_c, &str_n, &str_s);
+ /* -s NUM, -F imlies -f */
+ IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";)
+ opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"),
+ &str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period));
#define FOLLOW (opt & 0x1)
#define COUNT_BYTES (opt & 0x2)
//if (opt & 0x1) // -f
if (opt & 0x2) count = eat_num(str_c); // -c
if (opt & 0x4) count = eat_num(str_n); // -n
#if ENABLE_FEATURE_FANCY_TAIL
- if (opt & 0x8) header_threshhold = INT_MAX; // -q
- if (opt & 0x10) sleep_period = xatou(str_s); // -s
+ /* 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)
+#else
+# define FOLLOW_RETRY 0
#endif
argc -= optind;
argv += optind;
- from_top = status;
+ from_top = G.status; /* 1 if there was "-c +N" or "-n +N" */
+ G.status = EXIT_SUCCESS;
/* open all the files */
- fds = xmalloc(sizeof(int) * (argc + 1));
- status = nfiles = i = 0;
- if (argc == 0) {
+ fds = xmalloc(sizeof(fds[0]) * (argc + 1));
+ if (!argv[0]) {
struct stat statbuf;
- if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
+ if (fstat(STDIN_FILENO, &statbuf) == 0
+ && S_ISFIFO(statbuf.st_mode)
+ ) {
opt &= ~1; /* clear FOLLOW */
}
- *argv = (char *) bb_msg_standard_input;
- goto DO_STDIN;
+ argv[0] = (char *) bb_msg_standard_input;
}
-
+ nfiles = i = 0;
do {
- if (NOT_LONE_DASH(argv[i])) {
- fds[nfiles] = open(argv[i], O_RDONLY);
- if (fds[nfiles] < 0) {
- bb_perror_msg("%s", argv[i]);
- status = EXIT_FAILURE;
- continue;
- }
- } else {
- DO_STDIN: /* "-" */
- fds[nfiles] = STDIN_FILENO;
+ int fd = open_or_warn_stdin(argv[i]);
+ if (fd < 0 && !FOLLOW_RETRY) {
+ G.status = EXIT_FAILURE;
+ continue;
}
- argv[nfiles] = argv[i];
- ++nfiles;
+ fds[nfiles] = fd;
+ argv[nfiles++] = argv[i];
} while (++i < argc);
if (!nfiles)
bb_error_msg_and_die("no files");
+ /* prepare the buffer */
tailbufsize = BUFSIZ;
-
- /* tail the files */
if (!from_top && COUNT_BYTES) {
- if (tailbufsize < count) {
+ if (tailbufsize < count + BUFSIZ) {
tailbufsize = count + BUFSIZ;
}
}
+ tailbuf = xmalloc(tailbufsize);
- buf = tailbuf = xmalloc(tailbufsize);
-
- fmt = header_fmt + 1; /* Skip header leading newline on first output. */
+ /* tail the files */
+ 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;
- }
+ char *buf;
+ int taillen;
+ int newlines_seen;
+ unsigned seen;
+ int nread;
+ int fd = fds[i];
+
+ if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
+ continue; /* may happen with -E */
if (nfiles > header_threshhold) {
tail_xprint_header(fmt, argv[i]);
fmt = header_fmt;
}
+ if (!from_top) {
+ off_t current = lseek(fd, 0, SEEK_END);
+ if (current > 0) {
+ unsigned off;
+ if (COUNT_BYTES) {
+ /* 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) */
+ if (count == 0)
+ continue; /* showing zero bytes is easy :) */
+ current -= count;
+ if (current < 0)
+ current = 0;
+ xlseek(fd, current, SEEK_SET);
+ bb_copyfd_size(fd, STDOUT_FILENO, count);
+ continue;
+ }
+#if 1 /* This is technically incorrect for *LONG* strings, but very useful */
+ /* Optimizing count-lines case if the file is seekable.
+ * We assume the lines are <64k.
+ * (Users complain that tail takes too long
+ * on multi-gigabyte files) */
+ off = (count | 0xf); /* for small counts, be more paranoid */
+ if (off > (INT_MAX / (64*1024)))
+ off = (INT_MAX / (64*1024));
+ current -= off * (64*1024);
+ if (current < 0)
+ current = 0;
+ xlseek(fd, current, SEEK_SET);
+#endif
+ }
+ }
+
buf = tailbuf;
taillen = 0;
+ /* "We saw 1st line/byte".
+ * Used only by +N code ("start from Nth", 1-based): */
seen = 1;
- newline = 0;
-
- while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
+ newlines_seen = 0;
+ while ((nread = tail_read(fd, buf, tailbufsize-taillen)) > 0) {
if (from_top) {
- nwrite = nread;
+ int nwrite = nread;
if (seen < count) {
+ /* We need to skip a few more bytes/lines */
if (COUNT_BYTES) {
nwrite -= (count - seen);
seen = count;
} else {
- s = buf;
+ char *s = buf;
do {
--nwrite;
if (*s++ == '\n' && ++seen == count) {
} else if (count) {
if (COUNT_BYTES) {
taillen += nread;
- if (taillen > count) {
+ if (taillen > (int)count) {
memmove(tailbuf, tailbuf + taillen - count, count);
taillen = count;
}
} else {
int k = nread;
- int nbuf = 0;
+ int newlines_in_buf = 0;
- while (k) {
- --k;
+ do { /* count '\n' in last read */
+ k--;
if (buf[k] == '\n') {
- ++nbuf;
+ newlines_in_buf++;
}
- }
+ } while (k);
- if (newline + nbuf < count) {
- newline += nbuf;
+ if (newlines_seen + newlines_in_buf < (int)count) {
+ newlines_seen += newlines_in_buf;
taillen += nread;
-
} else {
- int extra = 0;
- if (buf[nread-1] != '\n') {
- extra = 1;
- }
+ int extra = (buf[nread-1] != '\n');
+ char *s;
- k = newline + nbuf + extra - count;
+ k = newlines_seen + newlines_in_buf + extra - count;
s = tailbuf;
while (k) {
if (*s == '\n') {
- --k;
+ k--;
}
- ++s;
+ s++;
}
-
taillen += nread - (s - tailbuf);
memmove(tailbuf, s, taillen);
- newline = count - extra;
+ newlines_seen = count - extra;
}
- if (tailbufsize < taillen + BUFSIZ) {
+ if (tailbufsize < (size_t)taillen + BUFSIZ) {
tailbufsize = taillen + BUFSIZ;
tailbuf = xrealloc(tailbuf, tailbufsize);
}
}
buf = tailbuf + taillen;
}
- }
-
+ } /* while (tail_read() > 0) */
if (!from_top) {
xwrite(STDOUT_FILENO, tailbuf, taillen);
}
-
- taillen = 0;
} while (++i < nfiles);
- buf = xrealloc(tailbuf, BUFSIZ);
+ tailbuf = xrealloc(tailbuf, BUFSIZ);
fmt = NULL;
if (FOLLOW) while (1) {
sleep(sleep_period);
+
i = 0;
do {
+ int nread;
+ const char *filename = argv[i];
+ int fd = fds[i];
+
+ if (FOLLOW_RETRY) {
+ struct stat sbuf, fsbuf;
+
+ if (fd < 0
+ || fstat(fd, &fsbuf) < 0
+ || stat(filename, &sbuf) < 0
+ || fsbuf.st_dev != sbuf.st_dev
+ || fsbuf.st_ino != sbuf.st_ino
+ ) {
+ int new_fd;
+
+ if (fd >= 0)
+ close(fd);
+ new_fd = open(filename, O_RDONLY);
+ if (new_fd >= 0) {
+ bb_error_msg("%s has %s; following end of new file",
+ filename, (fd < 0) ? "appeared" : "been replaced"
+ );
+ } else if (fd >= 0) {
+ bb_perror_msg("%s has become inaccessible", filename);
+ }
+ fds[i] = fd = new_fd;
+ }
+ }
+ if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
+ continue;
if (nfiles > header_threshhold) {
fmt = header_fmt;
}
- while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
+ while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) {
if (fmt) {
- tail_xprint_header(fmt, argv[i]);
+ tail_xprint_header(fmt, filename);
fmt = NULL;
}
- xwrite(STDOUT_FILENO, buf, nread);
+ xwrite(STDOUT_FILENO, tailbuf, nread);
}
} while (++i < nfiles);
}
-
- return status;
+ if (ENABLE_FEATURE_CLEAN_UP) {
+ free(fds);
+ }
+ return G.status;
}