[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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| 7 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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| 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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| 27 | #include <stdio.h>
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| 28 | #include <stdlib.h>
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| 29 | #include <string.h>
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| 30 | #include <ctype.h>
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| 31 | #include <unistd.h>
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| 32 | #include <fcntl.h>
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| 33 | #include <sys/stat.h>
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| 34 | #include "busybox.h"
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| 35 |
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| 36 | static const struct suffix_mult tail_suffixes[] = {
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| 37 | { "b", 512 },
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| 38 | { "k", 1024 },
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| 39 | { "m", 1048576 },
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| 40 | { NULL, 0 }
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| 41 | };
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| 42 |
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| 43 | static int status;
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| 44 |
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| 45 | static void tail_xprint_header(const char *fmt, const char *filename)
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| 46 | {
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| 47 | /* If we get an output error, there is really no sense in continuing. */
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| 48 | if (dprintf(STDOUT_FILENO, fmt, filename) < 0) {
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| 49 | bb_perror_nomsg_and_die();
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| 50 | }
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| 51 | }
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| 52 |
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| 53 | /* len should probably be size_t */
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| 54 | static void tail_xbb_full_write(const char *buf, size_t len)
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| 55 | {
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| 56 | /* If we get a write error, there is really no sense in continuing. */
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| 57 | if (bb_full_write(STDOUT_FILENO, buf, len) < 0) {
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| 58 | bb_perror_nomsg_and_die();
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| 59 | }
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| 60 | }
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| 61 |
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| 62 | static ssize_t tail_read(int fd, char *buf, size_t count)
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| 63 | {
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| 64 | ssize_t r;
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| 65 | off_t current,end;
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| 66 | struct stat sbuf;
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| 67 |
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| 68 | end = current = lseek(fd, 0, SEEK_CUR);
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| 69 | if (!fstat(fd, &sbuf))
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| 70 | end = sbuf.st_size;
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| 71 | lseek(fd, end < current ? 0 : current, SEEK_SET);
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| 72 | if ((r = safe_read(fd, buf, count)) < 0) {
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| 73 | bb_perror_msg(bb_msg_read_error);
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| 74 | status = EXIT_FAILURE;
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| 75 | }
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| 76 |
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| 77 | return r;
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| 78 | }
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| 79 |
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| 80 | static const char tail_opts[] =
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| 81 | "fn:c:"
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| 82 | #if ENABLE_FEATURE_FANCY_TAIL
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| 83 | "qs:v"
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| 84 | #endif
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| 85 | ;
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| 86 |
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| 87 | static const char header_fmt[] = "\n==> %s <==\n";
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| 88 |
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| 89 | int tail_main(int argc, char **argv)
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| 90 | {
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| 91 | long count = 10;
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| 92 | unsigned int sleep_period = 1;
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| 93 | int from_top = 0;
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| 94 | int follow = 0;
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| 95 | int header_threshhold = 1;
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| 96 | int count_bytes = 0;
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| 97 |
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| 98 | char *tailbuf;
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| 99 | size_t tailbufsize;
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| 100 | int taillen = 0;
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| 101 | int newline = 0;
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| 102 |
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| 103 | int *fds, nfiles, nread, nwrite, seen, i, opt;
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| 104 | char *s, *buf;
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| 105 | const char *fmt;
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| 106 |
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| 107 | #if !ENABLE_DEBUG_YANK_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
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| 108 | /* Allow legacy syntax of an initial numeric option without -n. */
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| 109 | if (argc >=2 && ((argv[1][0] == '+') || ((argv[1][0] == '-')
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| 110 | /* && (isdigit)(argv[1][1]) */
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| 111 | && (((unsigned int)(argv[1][1] - '0')) <= 9))))
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| 112 | {
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| 113 | optind = 2;
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| 114 | optarg = argv[1];
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| 115 | goto GET_COUNT;
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| 116 | }
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| 117 | #endif
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| 118 |
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| 119 | while ((opt = getopt(argc, argv, tail_opts)) > 0) {
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| 120 | switch (opt) {
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| 121 | case 'f':
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| 122 | follow = 1;
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| 123 | break;
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| 124 | case 'c':
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| 125 | count_bytes = 1;
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| 126 | /* FALLS THROUGH */
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| 127 | case 'n':
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| 128 | #if !ENABLE_DEBUG_YANK_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
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| 129 | GET_COUNT:
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| 130 | #endif
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| 131 | count = bb_xgetlarg10_sfx(optarg, tail_suffixes);
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| 132 | /* Note: Leading whitespace is an error trapped above. */
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| 133 | if (*optarg == '+') {
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| 134 | from_top = 1;
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| 135 | } else {
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| 136 | from_top = 0;
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| 137 | }
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| 138 | if (count < 0) {
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| 139 | count = -count;
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| 140 | }
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| 141 | break;
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| 142 | #if ENABLE_FEATURE_FANCY_TAIL
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| 143 | case 'q':
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| 144 | header_threshhold = INT_MAX;
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| 145 | break;
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| 146 | case 's':
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| 147 | sleep_period =bb_xgetularg10_bnd(optarg, 0, UINT_MAX);
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| 148 | break;
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| 149 | case 'v':
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| 150 | header_threshhold = 0;
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| 151 | break;
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| 152 | #endif
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| 153 | default:
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| 154 | bb_show_usage();
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| 155 | }
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| 156 | }
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| 157 |
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| 158 | /* open all the files */
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| 159 | fds = (int *)xmalloc(sizeof(int) * (argc - optind + 1));
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| 160 |
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| 161 | argv += optind;
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| 162 | nfiles = i = 0;
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| 163 |
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| 164 | if ((argc -= optind) == 0) {
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| 165 | struct stat statbuf;
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| 166 |
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| 167 | if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
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| 168 | follow = 0;
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| 169 | }
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| 170 | /* --argv; */
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| 171 | *argv = (char *) bb_msg_standard_input;
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| 172 | goto DO_STDIN;
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| 173 | }
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| 174 |
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| 175 | do {
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| 176 | if ((argv[i][0] == '-') && !argv[i][1]) {
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| 177 | DO_STDIN:
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| 178 | fds[nfiles] = STDIN_FILENO;
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| 179 | } else if ((fds[nfiles] = open(argv[i], O_RDONLY)) < 0) {
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| 180 | bb_perror_msg("%s", argv[i]);
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| 181 | status = EXIT_FAILURE;
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| 182 | continue;
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| 183 | }
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| 184 | argv[nfiles] = argv[i];
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| 185 | ++nfiles;
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| 186 | } while (++i < argc);
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| 187 |
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| 188 | if (!nfiles) {
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| 189 | bb_error_msg_and_die("no files");
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| 190 | }
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| 191 |
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| 192 | tailbufsize = BUFSIZ;
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| 193 |
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| 194 | /* tail the files */
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| 195 | if (from_top < count_bytes) { /* Each is 0 or 1, so true iff 0 < 1. */
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| 196 | /* Hence, !from_top && count_bytes */
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| 197 | if (tailbufsize < count) {
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| 198 | tailbufsize = count + BUFSIZ;
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| 199 | }
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| 200 | }
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| 201 |
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| 202 | buf = tailbuf = xmalloc(tailbufsize);
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| 203 |
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| 204 | fmt = header_fmt + 1; /* Skip header leading newline on first output. */
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| 205 | i = 0;
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| 206 | do {
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| 207 | /* Be careful. It would be possible to optimize the count-bytes
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| 208 | * case if the file is seekable. If you do though, remember that
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| 209 | * starting file position may not be the beginning of the file.
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| 210 | * Beware of backing up too far. See example in wc.c.
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| 211 | */
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| 212 | if ((!(count|from_top)) && (lseek(fds[i], 0, SEEK_END) >= 0)) {
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| 213 | continue;
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| 214 | }
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| 215 |
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| 216 | if (nfiles > header_threshhold) {
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| 217 | tail_xprint_header(fmt, argv[i]);
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| 218 | fmt = header_fmt;
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| 219 | }
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| 220 |
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| 221 | buf = tailbuf;
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| 222 | taillen = 0;
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| 223 | seen = 1;
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| 224 | newline = 0;
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| 225 |
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| 226 | while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
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| 227 | if (from_top) {
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| 228 | nwrite = nread;
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| 229 | if (seen < count) {
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| 230 | if (count_bytes) {
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| 231 | nwrite -= (count - seen);
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| 232 | seen = count;
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| 233 | } else {
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| 234 | s = buf;
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| 235 | do {
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| 236 | --nwrite;
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| 237 | if ((*s++ == '\n') && (++seen == count)) {
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| 238 | break;
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| 239 | }
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| 240 | } while (nwrite);
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| 241 | }
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| 242 | }
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| 243 | tail_xbb_full_write(buf + nread - nwrite, nwrite);
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| 244 | } else if (count) {
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| 245 | if (count_bytes) {
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| 246 | taillen += nread;
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| 247 | if (taillen > count) {
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| 248 | memmove(tailbuf, tailbuf + taillen - count, count);
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| 249 | taillen = count;
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| 250 | }
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| 251 | } else {
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| 252 | int k = nread;
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| 253 | int nbuf = 0;
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| 254 |
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| 255 | while (k) {
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| 256 | --k;
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| 257 | if (buf[k] == '\n') {
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| 258 | ++nbuf;
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| 259 | }
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| 260 | }
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| 261 |
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| 262 | if (newline + nbuf < count) {
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| 263 | newline += nbuf;
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| 264 | taillen += nread;
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| 265 |
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| 266 | } else {
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| 267 | int extra = 0;
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| 268 | if (buf[nread-1] != '\n') {
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| 269 | extra = 1;
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| 270 | }
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| 271 |
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| 272 | k = newline + nbuf + extra - count;
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| 273 | s = tailbuf;
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| 274 | while (k) {
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| 275 | if (*s == '\n') {
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| 276 | --k;
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| 277 | }
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| 278 | ++s;
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| 279 | }
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| 280 |
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| 281 | taillen += nread - (s - tailbuf);
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| 282 | memmove(tailbuf, s, taillen);
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| 283 | newline = count - extra;
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| 284 | }
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| 285 | if (tailbufsize < taillen + BUFSIZ) {
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| 286 | tailbufsize = taillen + BUFSIZ;
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| 287 | tailbuf = xrealloc(tailbuf, tailbufsize);
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| 288 | }
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| 289 | }
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| 290 | buf = tailbuf + taillen;
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| 291 | }
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| 292 | }
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| 293 |
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| 294 | if (!from_top) {
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| 295 | tail_xbb_full_write(tailbuf, taillen);
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| 296 | }
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| 297 |
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| 298 | taillen = 0;
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| 299 | } while (++i < nfiles);
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| 300 |
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| 301 | buf = xrealloc(tailbuf, BUFSIZ);
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| 302 |
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| 303 | fmt = NULL;
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| 304 |
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| 305 | while (follow) {
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| 306 | sleep(sleep_period);
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| 307 | i = 0;
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| 308 | do {
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| 309 | if (nfiles > header_threshhold) {
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| 310 | fmt = header_fmt;
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| 311 | }
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| 312 | while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
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| 313 | if (fmt) {
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| 314 | tail_xprint_header(fmt, argv[i]);
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| 315 | fmt = NULL;
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| 316 | }
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| 317 | tail_xbb_full_write(buf, nread);
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| 318 | }
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| 319 | } while (++i < nfiles);
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| 320 | }
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| 321 |
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| 322 | return status;
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| 323 | }
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