* 7) lseek attempted when count==0 even if arg was +0 (from top)
*/
-#include "libbb.h"
+//kbuild:lib-$(CONFIG_TAIL) += tail.o
+
+//usage:#define tail_trivial_usage
+//usage: "[OPTIONS] [FILE]..."
+//usage:#define tail_full_usage "\n\n"
+//usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n"
+//usage: "With more than one FILE, precede each with a filename header.\n"
+//usage: "\n -f Print data as file grows"
+//usage: IF_FEATURE_FANCY_TAIL(
+//usage: "\n -s SECONDS Wait SECONDS between reads with -f"
+//usage: )
+//usage: "\n -n N[kbm] Print last N lines"
+//usage: "\n -n +N[kbm] Start on Nth line and print the rest"
+//usage: IF_FEATURE_FANCY_TAIL(
+//usage: "\n -c [+]N[kbm] Print last N bytes"
+//usage: "\n -q Never print headers"
+//usage: "\n -v Always print headers"
+//usage: "\n"
+//usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
+//usage: )
+//usage:
+//usage:#define tail_example_usage
+//usage: "$ tail -n 1 /etc/resolv.conf\n"
+//usage: "nameserver 10.0.0.1\n"
-static const struct suffix_mult tail_suffixes[] = {
- { "b", 512 },
- { "k", 1024 },
- { "m", 1024*1024 },
- { "", 0 }
-};
+#include "libbb.h"
struct globals {
- bool status;
+ bool from_top;
+ bool exitcode;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
+#define INIT_G() do { } while (0)
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;
- struct stat sbuf;
-
- /* /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);
- G.status = EXIT_FAILURE;
+ G.exitcode = EXIT_FAILURE;
}
return r;
p++;
else if (*p == '+') {
p++;
- G.status = 1; /* mark that we saw "+" */
+ G.from_top = 1;
}
- return xatou_sfx(p, tail_suffixes);
+ return xatou_sfx(p, bkm_suffixes);
}
int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
{
unsigned count = 10;
unsigned sleep_period = 1;
- bool from_top;
const char *str_c, *str_n;
char *tailbuf;
int *fds;
const char *fmt;
+ int prev_fd;
+
+ INIT_G();
#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
/* Allow legacy syntax of an initial numeric option without -n. */
#endif
argc -= optind;
argv += optind;
- from_top = G.status; /* 1 if there was "-c +N" or "-n +N" */
- G.status = EXIT_SUCCESS;
/* open all the files */
fds = xmalloc(sizeof(fds[0]) * (argc + 1));
do {
int fd = open_or_warn_stdin(argv[i]);
if (fd < 0 && !FOLLOW_RETRY) {
- G.status = EXIT_FAILURE;
+ G.exitcode = EXIT_FAILURE;
continue;
}
fds[nfiles] = fd;
/* prepare the buffer */
tailbufsize = BUFSIZ;
- if (!from_top && COUNT_BYTES) {
+ if (!G.from_top && COUNT_BYTES) {
if (tailbufsize < count + BUFSIZ) {
tailbufsize = count + BUFSIZ;
}
}
- tailbuf = xmalloc(tailbufsize);
+ /* tail -c1024m REGULAR_FILE doesn't really need 1G mem block.
+ * (In fact, it doesn't need ANY memory). So delay allocation.
+ */
+ tailbuf = NULL;
/* tail the files */
- fmt = header_fmt_str + 1; /* skip header leading newline on first output */
+
+ fmt = header_fmt_str + 1; /* skip leading newline in the header on the first output */
i = 0;
do {
char *buf;
int fd = fds[i];
if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
- continue; /* may happen with -E */
+ continue; /* may happen with -F */
if (nfiles > header_threshhold) {
tail_xprint_header(fmt, argv[i]);
fmt = header_fmt_str;
}
- if (!from_top) {
+ if (!G.from_top) {
off_t current = lseek(fd, 0, SEEK_END);
if (current > 0) {
unsigned off;
}
}
+ if (!tailbuf)
+ tailbuf = xmalloc(tailbufsize);
+
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(fd, buf, tailbufsize-taillen)) > 0) {
- if (from_top) {
+ while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) {
+ if (G.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;
+ seen += nread;
} else {
char *s = buf;
do {
buf = tailbuf + taillen;
}
} /* while (tail_read() > 0) */
- if (!from_top) {
+ if (!G.from_top) {
xwrite(STDOUT_FILENO, tailbuf, taillen);
}
} while (++i < nfiles);
+ prev_fd = fds[i-1];
tailbuf = xrealloc(tailbuf, BUFSIZ);
if (nfiles > header_threshhold) {
fmt = header_fmt_str;
}
- while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) {
- if (fmt) {
+ for (;;) {
+ /* tail -f keeps following files even if they are truncated */
+ struct stat sbuf;
+ /* /proc files report zero st_size, don't lseek them */
+ if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
+ off_t current = lseek(fd, 0, SEEK_CUR);
+ if (sbuf.st_size < current)
+ xlseek(fd, 0, SEEK_SET);
+ }
+
+ nread = tail_read(fd, tailbuf, BUFSIZ);
+ if (nread <= 0)
+ break;
+ if (fmt && (fd != prev_fd)) {
tail_xprint_header(fmt, filename);
fmt = NULL;
+ prev_fd = fd;
}
xwrite(STDOUT_FILENO, tailbuf, nread);
}
} while (++i < nfiles);
- }
+ } /* while (1) */
+
if (ENABLE_FEATURE_CLEAN_UP) {
free(fds);
+ free(tailbuf);
}
- return G.status;
+ return G.exitcode;
}
projects / platform / upstream / busybox.git / blobdiff