407 lines
10 KiB
C
407 lines
10 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Mini tail implementation for busybox
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*
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* Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this source tree.
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*/
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/* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
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*
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* Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
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* Bugs fixed (although I may have forgotten one or two... it was pretty bad)
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* 1) mixing printf/write without fflush()ing stdout
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* 2) no check that any open files are present
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* 3) optstring had -q taking an arg
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* 4) no error checking on write in some cases, and a warning even then
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* 5) q and s interaction bug
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* 6) no check for lseek error
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* 7) lseek attempted when count==0 even if arg was +0 (from top)
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*/
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//config:config TAIL
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//config: bool "tail (6.8 kb)"
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//config: default y
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//config: help
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//config: tail is used to print the last specified number of lines
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//config: from files.
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//config:
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//config:config FEATURE_FANCY_TAIL
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//config: bool "Enable -q, -s, -v, and -F options"
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//config: default y
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//config: depends on TAIL
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//config: help
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//config: These options are provided by GNU tail, but
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//config: are not specified in the SUSv3 standard:
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//config: -q Never output headers giving file names
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//config: -s SEC Wait SEC seconds between reads with -f
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//config: -v Always output headers giving file names
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//config: -F Same as -f, but keep retrying
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//applet:IF_TAIL(APPLET(tail, BB_DIR_USR_BIN, BB_SUID_DROP))
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//kbuild:lib-$(CONFIG_TAIL) += tail.o
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/* BB_AUDIT SUSv3 compliant (need fancy for -c) */
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/* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
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/* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
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//usage:#define tail_trivial_usage
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//usage: "[OPTIONS] [FILE]..."
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//usage:#define tail_full_usage "\n\n"
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//usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n"
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//usage: "With more than one FILE, precede each with a filename header.\n"
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//usage: "\n -f Print data as file grows"
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//usage: "\n -c [+]N[kbm] Print last N bytes"
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//usage: "\n -n N[kbm] Print last N lines"
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//usage: "\n -n +N[kbm] Start on Nth line and print the rest"
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//usage: IF_FEATURE_FANCY_TAIL(
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//usage: "\n -q Never print headers"
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//usage: "\n -s SECONDS Wait SECONDS between reads with -f"
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//usage: "\n -v Always print headers"
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//usage: "\n -F Same as -f, but keep retrying"
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//usage: "\n"
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//usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
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//usage: )
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//usage:
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//usage:#define tail_example_usage
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//usage: "$ tail -n 1 /etc/resolv.conf\n"
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//usage: "nameserver 10.0.0.1\n"
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#include "libbb.h"
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#include "common_bufsiz.h"
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struct globals {
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bool from_top;
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bool exitcode;
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} FIX_ALIASING;
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#define G (*(struct globals*)bb_common_bufsiz1)
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#define INIT_G() do { setup_common_bufsiz(); } while (0)
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static void tail_xprint_header(const char *fmt, const char *filename)
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{
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if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
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bb_perror_nomsg_and_die();
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}
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static ssize_t tail_read(int fd, char *buf, size_t count)
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{
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ssize_t r;
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r = full_read(fd, buf, count);
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if (r < 0) {
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bb_perror_msg(bb_msg_read_error);
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G.exitcode = EXIT_FAILURE;
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}
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return r;
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}
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#define header_fmt_str "\n==> %s <==\n"
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static unsigned eat_num(const char *p)
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{
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if (*p == '-')
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p++;
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else if (*p == '+') {
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p++;
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G.from_top = 1;
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}
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return xatou_sfx(p, bkm_suffixes);
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}
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int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int tail_main(int argc, char **argv)
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{
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unsigned count = 10;
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unsigned sleep_period = 1;
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const char *str_c, *str_n;
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char *tailbuf;
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size_t tailbufsize;
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unsigned header_threshhold = 1;
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unsigned nfiles;
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int i, opt;
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int *fds;
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const char *fmt;
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int prev_fd;
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INIT_G();
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#if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
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/* Allow legacy syntax of an initial numeric option without -n. */
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if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-')
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&& isdigit(argv[1][1])
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) {
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count = eat_num(argv[1]);
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argv++;
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argc--;
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}
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#endif
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/* -s NUM, -F imlies -f */
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opt = getopt32(argv, IF_FEATURE_FANCY_TAIL("^")
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"fc:n:"IF_FEATURE_FANCY_TAIL("qs:+vF")
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IF_FEATURE_FANCY_TAIL("\0" "Ff"),
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&str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period)
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);
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#define FOLLOW (opt & 0x1)
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#define COUNT_BYTES (opt & 0x2)
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//if (opt & 0x1) // -f
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if (opt & 0x2) count = eat_num(str_c); // -c
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if (opt & 0x4) count = eat_num(str_n); // -n
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#if ENABLE_FEATURE_FANCY_TAIL
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/* q: make it impossible for nfiles to be > header_threshhold */
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if (opt & 0x8) header_threshhold = UINT_MAX; // -q
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//if (opt & 0x10) // -s
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if (opt & 0x20) header_threshhold = 0; // -v
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# define FOLLOW_RETRY (opt & 0x40)
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#else
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# define FOLLOW_RETRY 0
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#endif
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argc -= optind;
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argv += optind;
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/* open all the files */
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fds = xmalloc(sizeof(fds[0]) * (argc + 1));
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if (!argv[0]) {
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struct stat statbuf;
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if (fstat(STDIN_FILENO, &statbuf) == 0
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&& S_ISFIFO(statbuf.st_mode)
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) {
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opt &= ~1; /* clear FOLLOW */
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}
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argv[0] = (char *) bb_msg_standard_input;
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}
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nfiles = i = 0;
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do {
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int fd = open_or_warn_stdin(argv[i]);
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if (fd < 0 && !FOLLOW_RETRY) {
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G.exitcode = EXIT_FAILURE;
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continue;
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}
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fds[nfiles] = fd;
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argv[nfiles++] = argv[i];
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} while (++i < argc);
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if (!nfiles)
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bb_error_msg_and_die("no files");
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/* prepare the buffer */
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tailbufsize = BUFSIZ;
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if (!G.from_top && COUNT_BYTES) {
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if (tailbufsize < count + BUFSIZ) {
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tailbufsize = count + BUFSIZ;
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}
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}
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/* tail -c1024m REGULAR_FILE doesn't really need 1G mem block.
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* (In fact, it doesn't need ANY memory). So delay allocation.
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*/
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tailbuf = NULL;
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/* tail the files */
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fmt = header_fmt_str + 1; /* skip leading newline in the header on the first output */
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i = 0;
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do {
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char *buf;
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int taillen;
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int newlines_seen;
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unsigned seen;
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int nread;
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int fd = fds[i];
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if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
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continue; /* may happen with -F */
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if (nfiles > header_threshhold) {
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tail_xprint_header(fmt, argv[i]);
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fmt = header_fmt_str;
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}
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if (!G.from_top) {
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off_t current = lseek(fd, 0, SEEK_END);
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if (current > 0) {
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unsigned off;
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if (COUNT_BYTES) {
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/* Optimizing count-bytes case if the file is seekable.
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* Beware of backing up too far.
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* Also we exclude files with size 0 (because of /proc/xxx) */
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if (count == 0)
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continue; /* showing zero bytes is easy :) */
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current -= count;
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if (current < 0)
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current = 0;
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xlseek(fd, current, SEEK_SET);
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bb_copyfd_size(fd, STDOUT_FILENO, count);
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continue;
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}
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#if 1 /* This is technically incorrect for *LONG* strings, but very useful */
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/* Optimizing count-lines case if the file is seekable.
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* We assume the lines are <64k.
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* (Users complain that tail takes too long
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* on multi-gigabyte files) */
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off = (count | 0xf); /* for small counts, be more paranoid */
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if (off > (INT_MAX / (64*1024)))
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off = (INT_MAX / (64*1024));
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current -= off * (64*1024);
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if (current < 0)
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current = 0;
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xlseek(fd, current, SEEK_SET);
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#endif
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}
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}
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if (!tailbuf)
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tailbuf = xmalloc(tailbufsize);
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buf = tailbuf;
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taillen = 0;
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/* "We saw 1st line/byte".
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* Used only by +N code ("start from Nth", 1-based): */
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seen = 1;
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newlines_seen = 0;
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while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) {
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if (G.from_top) {
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int nwrite = nread;
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if (seen < count) {
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/* We need to skip a few more bytes/lines */
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if (COUNT_BYTES) {
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nwrite -= (count - seen);
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seen += nread;
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} else {
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char *s = buf;
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do {
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--nwrite;
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if (*s++ == '\n' && ++seen == count) {
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break;
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}
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} while (nwrite);
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}
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}
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if (nwrite > 0)
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xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
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} else if (count) {
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if (COUNT_BYTES) {
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taillen += nread;
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if (taillen > (int)count) {
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memmove(tailbuf, tailbuf + taillen - count, count);
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taillen = count;
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}
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} else {
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int k = nread;
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int newlines_in_buf = 0;
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do { /* count '\n' in last read */
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k--;
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if (buf[k] == '\n') {
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newlines_in_buf++;
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}
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} while (k);
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if (newlines_seen + newlines_in_buf < (int)count) {
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newlines_seen += newlines_in_buf;
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taillen += nread;
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} else {
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int extra = (buf[nread-1] != '\n');
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char *s;
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k = newlines_seen + newlines_in_buf + extra - count;
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s = tailbuf;
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while (k) {
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if (*s == '\n') {
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k--;
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}
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s++;
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}
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taillen += nread - (s - tailbuf);
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memmove(tailbuf, s, taillen);
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newlines_seen = count - extra;
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}
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if (tailbufsize < (size_t)taillen + BUFSIZ) {
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tailbufsize = taillen + BUFSIZ;
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tailbuf = xrealloc(tailbuf, tailbufsize);
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}
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}
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buf = tailbuf + taillen;
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}
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} /* while (tail_read() > 0) */
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if (!G.from_top) {
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xwrite(STDOUT_FILENO, tailbuf, taillen);
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}
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} while (++i < nfiles);
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prev_fd = fds[i-1];
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tailbuf = xrealloc(tailbuf, BUFSIZ);
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fmt = NULL;
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if (FOLLOW) while (1) {
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sleep(sleep_period);
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i = 0;
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do {
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int nread;
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const char *filename = argv[i];
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int fd = fds[i];
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if (FOLLOW_RETRY) {
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struct stat sbuf, fsbuf;
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if (fd < 0
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|| fstat(fd, &fsbuf) < 0
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|| stat(filename, &sbuf) < 0
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|| fsbuf.st_dev != sbuf.st_dev
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|| fsbuf.st_ino != sbuf.st_ino
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) {
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int new_fd;
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if (fd >= 0)
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close(fd);
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new_fd = open(filename, O_RDONLY);
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if (new_fd >= 0) {
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bb_error_msg("%s has %s; following end of new file",
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filename, (fd < 0) ? "appeared" : "been replaced"
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);
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} else if (fd >= 0) {
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bb_perror_msg("%s has become inaccessible", filename);
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}
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fds[i] = fd = new_fd;
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}
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}
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if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
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continue;
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if (nfiles > header_threshhold) {
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fmt = header_fmt_str;
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}
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for (;;) {
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/* tail -f keeps following files even if they are truncated */
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struct stat sbuf;
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/* /proc files report zero st_size, don't lseek them */
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if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
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off_t current = lseek(fd, 0, SEEK_CUR);
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if (sbuf.st_size < current)
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xlseek(fd, 0, SEEK_SET);
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}
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nread = tail_read(fd, tailbuf, BUFSIZ);
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if (nread <= 0)
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break;
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if (fmt && (fd != prev_fd)) {
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tail_xprint_header(fmt, filename);
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fmt = NULL;
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prev_fd = fd;
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}
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xwrite(STDOUT_FILENO, tailbuf, nread);
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}
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} while (++i < nfiles);
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} /* while (1) */
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if (ENABLE_FEATURE_CLEAN_UP) {
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free(fds);
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free(tailbuf);
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}
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return G.exitcode;
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}
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