[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Mini tail implementation for busybox
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| 4 | *
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| 5 | * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
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| 6 | *
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[2725] | 7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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[821] | 8 | */
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| 9 |
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| 10 | /* BB_AUDIT SUSv3 compliant (need fancy for -c) */
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| 11 | /* BB_AUDIT GNU compatible -c, -q, and -v options in 'fancy' configuration. */
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| 12 | /* http://www.opengroup.org/onlinepubs/007904975/utilities/tail.html */
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| 13 |
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| 14 | /* Mar 16, 2003 Manuel Novoa III (mjn3@codepoet.org)
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| 15 | *
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| 16 | * Pretty much rewritten to fix numerous bugs and reduce realloc() calls.
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| 17 | * Bugs fixed (although I may have forgotten one or two... it was pretty bad)
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| 18 | * 1) mixing printf/write without fflush()ing stdout
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| 19 | * 2) no check that any open files are present
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| 20 | * 3) optstring had -q taking an arg
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| 21 | * 4) no error checking on write in some cases, and a warning even then
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| 22 | * 5) q and s interaction bug
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| 23 | * 6) no check for lseek error
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| 24 | * 7) lseek attempted when count==0 even if arg was +0 (from top)
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| 25 | */
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| 26 |
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[3232] | 27 | //usage:#define tail_trivial_usage
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| 28 | //usage: "[OPTIONS] [FILE]..."
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| 29 | //usage:#define tail_full_usage "\n\n"
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| 30 | //usage: "Print last 10 lines of each FILE (or stdin) to stdout.\n"
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| 31 | //usage: "With more than one FILE, precede each with a filename header.\n"
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| 32 | //usage: "\n -f Print data as file grows"
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| 33 | //usage: IF_FEATURE_FANCY_TAIL(
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| 34 | //usage: "\n -s SECONDS Wait SECONDS between reads with -f"
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| 35 | //usage: )
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| 36 | //usage: "\n -n N[kbm] Print last N lines"
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| 37 | //usage: IF_FEATURE_FANCY_TAIL(
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| 38 | //usage: "\n -c N[kbm] Print last N bytes"
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| 39 | //usage: "\n -q Never print headers"
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| 40 | //usage: "\n -v Always print headers"
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| 41 | //usage: "\n"
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| 42 | //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
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| 43 | //usage: "\nIf N starts with a '+', output begins with the Nth item from the start"
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| 44 | //usage: "\nof each file, not from the end."
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| 45 | //usage: )
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| 46 | //usage:
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| 47 | //usage:#define tail_example_usage
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| 48 | //usage: "$ tail -n 1 /etc/resolv.conf\n"
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| 49 | //usage: "nameserver 10.0.0.1\n"
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| 50 |
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[1765] | 51 | #include "libbb.h"
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[821] | 52 |
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| 53 | static const struct suffix_mult tail_suffixes[] = {
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| 54 | { "b", 512 },
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| 55 | { "k", 1024 },
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[1765] | 56 | { "m", 1024*1024 },
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[2725] | 57 | { "", 0 }
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[821] | 58 | };
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| 59 |
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[1765] | 60 | struct globals {
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[3232] | 61 | bool from_top;
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| 62 | bool exitcode;
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[2725] | 63 | } FIX_ALIASING;
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[1765] | 64 | #define G (*(struct globals*)&bb_common_bufsiz1)
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[3232] | 65 | #define INIT_G() do { } while (0)
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[821] | 66 |
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| 67 | static void tail_xprint_header(const char *fmt, const char *filename)
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| 68 | {
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[1765] | 69 | if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
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[821] | 70 | bb_perror_nomsg_and_die();
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| 71 | }
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| 72 |
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| 73 | static ssize_t tail_read(int fd, char *buf, size_t count)
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| 74 | {
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| 75 | ssize_t r;
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[1772] | 76 | off_t current;
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[821] | 77 | struct stat sbuf;
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| 78 |
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[1772] | 79 | /* /proc files report zero st_size, don't lseek them. */
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[2725] | 80 | if (fstat(fd, &sbuf) == 0 && sbuf.st_size > 0) {
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| 81 | current = lseek(fd, 0, SEEK_CUR);
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[1772] | 82 | if (sbuf.st_size < current)
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[2725] | 83 | xlseek(fd, 0, SEEK_SET);
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| 84 | }
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[1772] | 85 |
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[2725] | 86 | r = full_read(fd, buf, count);
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[1765] | 87 | if (r < 0) {
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[821] | 88 | bb_perror_msg(bb_msg_read_error);
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[3232] | 89 | G.exitcode = EXIT_FAILURE;
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[821] | 90 | }
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| 91 |
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| 92 | return r;
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| 93 | }
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| 94 |
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[2725] | 95 | #define header_fmt_str "\n==> %s <==\n"
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[821] | 96 |
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[1765] | 97 | static unsigned eat_num(const char *p)
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| 98 | {
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[1772] | 99 | if (*p == '-')
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| 100 | p++;
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| 101 | else if (*p == '+') {
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| 102 | p++;
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[3232] | 103 | G.from_top = 1;
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[1772] | 104 | }
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[1765] | 105 | return xatou_sfx(p, tail_suffixes);
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| 106 | }
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[821] | 107 |
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[2725] | 108 | int tail_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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[821] | 109 | int tail_main(int argc, char **argv)
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| 110 | {
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[1765] | 111 | unsigned count = 10;
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| 112 | unsigned sleep_period = 1;
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| 113 | const char *str_c, *str_n;
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[821] | 114 |
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| 115 | char *tailbuf;
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| 116 | size_t tailbufsize;
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[2725] | 117 | unsigned header_threshhold = 1;
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| 118 | unsigned nfiles;
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| 119 | int i, opt;
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[821] | 120 |
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[1765] | 121 | int *fds;
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[821] | 122 | const char *fmt;
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| 123 |
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[3232] | 124 | INIT_G();
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| 125 |
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[1765] | 126 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
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[821] | 127 | /* Allow legacy syntax of an initial numeric option without -n. */
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[2725] | 128 | if (argv[1] && (argv[1][0] == '+' || argv[1][0] == '-')
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[1765] | 129 | && isdigit(argv[1][1])
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| 130 | ) {
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[2725] | 131 | count = eat_num(argv[1]);
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| 132 | argv++;
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| 133 | argc--;
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[821] | 134 | }
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| 135 | #endif
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| 136 |
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[2725] | 137 | /* -s NUM, -F imlies -f */
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| 138 | IF_FEATURE_FANCY_TAIL(opt_complementary = "s+:Ff";)
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| 139 | opt = getopt32(argv, "fc:n:" IF_FEATURE_FANCY_TAIL("qs:vF"),
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| 140 | &str_c, &str_n IF_FEATURE_FANCY_TAIL(,&sleep_period));
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[1765] | 141 | #define FOLLOW (opt & 0x1)
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| 142 | #define COUNT_BYTES (opt & 0x2)
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| 143 | //if (opt & 0x1) // -f
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| 144 | if (opt & 0x2) count = eat_num(str_c); // -c
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| 145 | if (opt & 0x4) count = eat_num(str_n); // -n
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[821] | 146 | #if ENABLE_FEATURE_FANCY_TAIL
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[2725] | 147 | /* q: make it impossible for nfiles to be > header_threshhold */
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| 148 | if (opt & 0x8) header_threshhold = UINT_MAX; // -q
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| 149 | //if (opt & 0x10) // -s
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[1765] | 150 | if (opt & 0x20) header_threshhold = 0; // -v
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[2725] | 151 | # define FOLLOW_RETRY (opt & 0x40)
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| 152 | #else
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| 153 | # define FOLLOW_RETRY 0
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[821] | 154 | #endif
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[1765] | 155 | argc -= optind;
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| 156 | argv += optind;
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[821] | 157 |
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| 158 | /* open all the files */
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[2725] | 159 | fds = xmalloc(sizeof(fds[0]) * (argc + 1));
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| 160 | if (!argv[0]) {
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[821] | 161 | struct stat statbuf;
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| 162 |
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[2725] | 163 | if (fstat(STDIN_FILENO, &statbuf) == 0
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| 164 | && S_ISFIFO(statbuf.st_mode)
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| 165 | ) {
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[1765] | 166 | opt &= ~1; /* clear FOLLOW */
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[821] | 167 | }
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[2725] | 168 | argv[0] = (char *) bb_msg_standard_input;
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[821] | 169 | }
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[2725] | 170 | nfiles = i = 0;
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[821] | 171 | do {
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[2725] | 172 | int fd = open_or_warn_stdin(argv[i]);
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| 173 | if (fd < 0 && !FOLLOW_RETRY) {
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[3232] | 174 | G.exitcode = EXIT_FAILURE;
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[821] | 175 | continue;
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| 176 | }
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[2725] | 177 | fds[nfiles] = fd;
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[1765] | 178 | argv[nfiles++] = argv[i];
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[821] | 179 | } while (++i < argc);
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| 180 |
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[1765] | 181 | if (!nfiles)
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[821] | 182 | bb_error_msg_and_die("no files");
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| 183 |
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[2725] | 184 | /* prepare the buffer */
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[821] | 185 | tailbufsize = BUFSIZ;
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[3232] | 186 | if (!G.from_top && COUNT_BYTES) {
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[2725] | 187 | if (tailbufsize < count + BUFSIZ) {
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[821] | 188 | tailbufsize = count + BUFSIZ;
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| 189 | }
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| 190 | }
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[3232] | 191 | /* tail -c1024m REGULAR_FILE doesn't really need 1G mem block.
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| 192 | * (In fact, it doesn't need ANY memory). So delay allocation.
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| 193 | */
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| 194 | tailbuf = NULL;
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[821] | 195 |
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[2725] | 196 | /* tail the files */
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[3232] | 197 |
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| 198 | fmt = header_fmt_str + 1; /* skip leading newline in the header on the first output */
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[821] | 199 | i = 0;
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| 200 | do {
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[2725] | 201 | char *buf;
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| 202 | int taillen;
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| 203 | int newlines_seen;
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| 204 | unsigned seen;
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| 205 | int nread;
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| 206 | int fd = fds[i];
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[821] | 207 |
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[2725] | 208 | if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
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[3232] | 209 | continue; /* may happen with -F */
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[2725] | 210 |
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[821] | 211 | if (nfiles > header_threshhold) {
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| 212 | tail_xprint_header(fmt, argv[i]);
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[2725] | 213 | fmt = header_fmt_str;
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[821] | 214 | }
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| 215 |
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[3232] | 216 | if (!G.from_top) {
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[2725] | 217 | off_t current = lseek(fd, 0, SEEK_END);
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| 218 | if (current > 0) {
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| 219 | unsigned off;
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| 220 | if (COUNT_BYTES) {
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| 221 | /* Optimizing count-bytes case if the file is seekable.
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| 222 | * Beware of backing up too far.
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| 223 | * Also we exclude files with size 0 (because of /proc/xxx) */
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| 224 | if (count == 0)
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| 225 | continue; /* showing zero bytes is easy :) */
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| 226 | current -= count;
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| 227 | if (current < 0)
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| 228 | current = 0;
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| 229 | xlseek(fd, current, SEEK_SET);
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| 230 | bb_copyfd_size(fd, STDOUT_FILENO, count);
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| 231 | continue;
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| 232 | }
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| 233 | #if 1 /* This is technically incorrect for *LONG* strings, but very useful */
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| 234 | /* Optimizing count-lines case if the file is seekable.
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| 235 | * We assume the lines are <64k.
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| 236 | * (Users complain that tail takes too long
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| 237 | * on multi-gigabyte files) */
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| 238 | off = (count | 0xf); /* for small counts, be more paranoid */
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| 239 | if (off > (INT_MAX / (64*1024)))
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| 240 | off = (INT_MAX / (64*1024));
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| 241 | current -= off * (64*1024);
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| 242 | if (current < 0)
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| 243 | current = 0;
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| 244 | xlseek(fd, current, SEEK_SET);
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| 245 | #endif
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| 246 | }
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| 247 | }
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| 248 |
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[3232] | 249 | if (!tailbuf)
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| 250 | tailbuf = xmalloc(tailbufsize);
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| 251 |
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[821] | 252 | buf = tailbuf;
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| 253 | taillen = 0;
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[2725] | 254 | /* "We saw 1st line/byte".
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| 255 | * Used only by +N code ("start from Nth", 1-based): */
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[821] | 256 | seen = 1;
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[2725] | 257 | newlines_seen = 0;
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[3232] | 258 | while ((nread = tail_read(fd, buf, tailbufsize - taillen)) > 0) {
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| 259 | if (G.from_top) {
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[2725] | 260 | int nwrite = nread;
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[821] | 261 | if (seen < count) {
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[2725] | 262 | /* We need to skip a few more bytes/lines */
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[1765] | 263 | if (COUNT_BYTES) {
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[821] | 264 | nwrite -= (count - seen);
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[3232] | 265 | seen += nread;
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[821] | 266 | } else {
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[2725] | 267 | char *s = buf;
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[821] | 268 | do {
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| 269 | --nwrite;
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[1765] | 270 | if (*s++ == '\n' && ++seen == count) {
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[821] | 271 | break;
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| 272 | }
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| 273 | } while (nwrite);
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| 274 | }
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| 275 | }
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[2725] | 276 | if (nwrite > 0)
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| 277 | xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
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[821] | 278 | } else if (count) {
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[1765] | 279 | if (COUNT_BYTES) {
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[821] | 280 | taillen += nread;
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[2725] | 281 | if (taillen > (int)count) {
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[821] | 282 | memmove(tailbuf, tailbuf + taillen - count, count);
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| 283 | taillen = count;
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| 284 | }
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| 285 | } else {
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| 286 | int k = nread;
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[2725] | 287 | int newlines_in_buf = 0;
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[821] | 288 |
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[2725] | 289 | do { /* count '\n' in last read */
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| 290 | k--;
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[821] | 291 | if (buf[k] == '\n') {
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[2725] | 292 | newlines_in_buf++;
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[821] | 293 | }
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[2725] | 294 | } while (k);
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[821] | 295 |
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[2725] | 296 | if (newlines_seen + newlines_in_buf < (int)count) {
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| 297 | newlines_seen += newlines_in_buf;
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[821] | 298 | taillen += nread;
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| 299 | } else {
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[2725] | 300 | int extra = (buf[nread-1] != '\n');
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| 301 | char *s;
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[1765] | 302 |
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[2725] | 303 | k = newlines_seen + newlines_in_buf + extra - count;
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[821] | 304 | s = tailbuf;
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| 305 | while (k) {
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| 306 | if (*s == '\n') {
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[2725] | 307 | k--;
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[821] | 308 | }
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[2725] | 309 | s++;
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[821] | 310 | }
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| 311 | taillen += nread - (s - tailbuf);
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| 312 | memmove(tailbuf, s, taillen);
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[2725] | 313 | newlines_seen = count - extra;
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[821] | 314 | }
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[2725] | 315 | if (tailbufsize < (size_t)taillen + BUFSIZ) {
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[821] | 316 | tailbufsize = taillen + BUFSIZ;
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| 317 | tailbuf = xrealloc(tailbuf, tailbufsize);
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| 318 | }
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| 319 | }
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| 320 | buf = tailbuf + taillen;
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| 321 | }
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[2725] | 322 | } /* while (tail_read() > 0) */
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[3232] | 323 | if (!G.from_top) {
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[1765] | 324 | xwrite(STDOUT_FILENO, tailbuf, taillen);
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[821] | 325 | }
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| 326 | } while (++i < nfiles);
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| 327 |
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[2725] | 328 | tailbuf = xrealloc(tailbuf, BUFSIZ);
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[821] | 329 |
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| 330 | fmt = NULL;
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| 331 |
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[1765] | 332 | if (FOLLOW) while (1) {
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[821] | 333 | sleep(sleep_period);
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[2725] | 334 |
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[821] | 335 | i = 0;
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| 336 | do {
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[2725] | 337 | int nread;
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| 338 | const char *filename = argv[i];
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| 339 | int fd = fds[i];
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| 340 |
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| 341 | if (FOLLOW_RETRY) {
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| 342 | struct stat sbuf, fsbuf;
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| 343 |
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| 344 | if (fd < 0
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| 345 | || fstat(fd, &fsbuf) < 0
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| 346 | || stat(filename, &sbuf) < 0
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| 347 | || fsbuf.st_dev != sbuf.st_dev
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| 348 | || fsbuf.st_ino != sbuf.st_ino
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| 349 | ) {
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| 350 | int new_fd;
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| 351 |
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| 352 | if (fd >= 0)
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| 353 | close(fd);
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| 354 | new_fd = open(filename, O_RDONLY);
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| 355 | if (new_fd >= 0) {
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| 356 | bb_error_msg("%s has %s; following end of new file",
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| 357 | filename, (fd < 0) ? "appeared" : "been replaced"
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| 358 | );
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| 359 | } else if (fd >= 0) {
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| 360 | bb_perror_msg("%s has become inaccessible", filename);
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| 361 | }
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| 362 | fds[i] = fd = new_fd;
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| 363 | }
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| 364 | }
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| 365 | if (ENABLE_FEATURE_FANCY_TAIL && fd < 0)
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| 366 | continue;
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[821] | 367 | if (nfiles > header_threshhold) {
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[2725] | 368 | fmt = header_fmt_str;
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[821] | 369 | }
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[2725] | 370 | while ((nread = tail_read(fd, tailbuf, BUFSIZ)) > 0) {
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[821] | 371 | if (fmt) {
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[2725] | 372 | tail_xprint_header(fmt, filename);
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[821] | 373 | fmt = NULL;
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| 374 | }
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[2725] | 375 | xwrite(STDOUT_FILENO, tailbuf, nread);
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[821] | 376 | }
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| 377 | } while (++i < nfiles);
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[3232] | 378 | } /* while (1) */
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| 379 |
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[1765] | 380 | if (ENABLE_FEATURE_CLEAN_UP) {
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| 381 | free(fds);
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[2725] | 382 | free(tailbuf);
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[1765] | 383 | }
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[3232] | 384 | return G.exitcode;
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[821] | 385 | }
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