[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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[1770] | 27 | #include "libbb.h"
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[821] | 28 |
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| 29 | static const struct suffix_mult tail_suffixes[] = {
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| 30 | { "b", 512 },
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| 31 | { "k", 1024 },
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[1770] | 32 | { "m", 1024*1024 },
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| 33 | { }
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[821] | 34 | };
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| 35 |
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[1770] | 36 | struct globals {
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| 37 | bool status;
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| 38 | };
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| 39 | #define G (*(struct globals*)&bb_common_bufsiz1)
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[821] | 40 |
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| 41 | static void tail_xprint_header(const char *fmt, const char *filename)
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| 42 | {
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[1770] | 43 | if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
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[821] | 44 | bb_perror_nomsg_and_die();
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| 45 | }
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| 46 |
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| 47 | static ssize_t tail_read(int fd, char *buf, size_t count)
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| 48 | {
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| 49 | ssize_t r;
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[1842] | 50 | off_t current;
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[821] | 51 | struct stat sbuf;
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| 52 |
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[1842] | 53 | /* (A good comment is missing here) */
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| 54 | current = lseek(fd, 0, SEEK_CUR);
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| 55 | /* /proc files report zero st_size, don't lseek them. */
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| 56 | if (fstat(fd, &sbuf) == 0 && sbuf.st_size)
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| 57 | if (sbuf.st_size < current)
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| 58 | lseek(fd, 0, SEEK_SET);
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| 59 |
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[1770] | 60 | r = safe_read(fd, buf, count);
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| 61 | if (r < 0) {
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[821] | 62 | bb_perror_msg(bb_msg_read_error);
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[1770] | 63 | G.status = EXIT_FAILURE;
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[821] | 64 | }
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| 65 |
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| 66 | return r;
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| 67 | }
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| 68 |
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[1770] | 69 | static const char header_fmt[] ALIGN1 = "\n==> %s <==\n";
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[821] | 70 |
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[1770] | 71 | static unsigned eat_num(const char *p)
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| 72 | {
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[1842] | 73 | if (*p == '-')
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| 74 | p++;
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| 75 | else if (*p == '+') {
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| 76 | p++;
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| 77 | G.status = EXIT_FAILURE;
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| 78 | }
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[1770] | 79 | return xatou_sfx(p, tail_suffixes);
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| 80 | }
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[821] | 81 |
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[1770] | 82 | int tail_main(int argc, char **argv);
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[821] | 83 | int tail_main(int argc, char **argv)
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| 84 | {
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[1770] | 85 | unsigned count = 10;
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| 86 | unsigned sleep_period = 1;
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| 87 | bool from_top;
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[821] | 88 | int header_threshhold = 1;
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[1770] | 89 | const char *str_c, *str_n;
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| 90 | USE_FEATURE_FANCY_TAIL(const char *str_s;)
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[821] | 91 |
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| 92 | char *tailbuf;
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| 93 | size_t tailbufsize;
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| 94 | int taillen = 0;
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| 95 | int newline = 0;
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[1770] | 96 | int nfiles, nread, nwrite, seen, i, opt;
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[821] | 97 |
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[1770] | 98 | int *fds;
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[821] | 99 | char *s, *buf;
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| 100 | const char *fmt;
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| 101 |
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[1770] | 102 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
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[821] | 103 | /* Allow legacy syntax of an initial numeric option without -n. */
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[1770] | 104 | if (argc >= 2 && (argv[1][0] == '+' || argv[1][0] == '-')
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| 105 | && isdigit(argv[1][1])
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| 106 | ) {
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| 107 | /* replacing arg[0] with "-n" can segfault, so... */
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| 108 | argv[1] = xasprintf("-n%s", argv[1]);
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| 109 | #if 0 /* If we ever decide to make tail NOFORK */
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| 110 | char *s = alloca(strlen(argv[1]) + 3);
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| 111 | sprintf(s, "-n%s", argv[1]);
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| 112 | argv[1] = s;
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| 113 | #endif
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[821] | 114 | }
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| 115 | #endif
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| 116 |
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[1770] | 117 | opt = getopt32(argv, "fc:n:" USE_FEATURE_FANCY_TAIL("qs:v"),
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| 118 | &str_c, &str_n USE_FEATURE_FANCY_TAIL(,&str_s));
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| 119 | #define FOLLOW (opt & 0x1)
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| 120 | #define COUNT_BYTES (opt & 0x2)
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| 121 | //if (opt & 0x1) // -f
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| 122 | if (opt & 0x2) count = eat_num(str_c); // -c
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| 123 | if (opt & 0x4) count = eat_num(str_n); // -n
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[821] | 124 | #if ENABLE_FEATURE_FANCY_TAIL
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[1770] | 125 | if (opt & 0x8) header_threshhold = INT_MAX; // -q
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| 126 | if (opt & 0x10) sleep_period = xatou(str_s); // -s
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| 127 | if (opt & 0x20) header_threshhold = 0; // -v
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[821] | 128 | #endif
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[1770] | 129 | argc -= optind;
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| 130 | argv += optind;
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| 131 | from_top = G.status;
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[821] | 132 |
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| 133 | /* open all the files */
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[1770] | 134 | fds = xmalloc(sizeof(int) * (argc + 1));
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[821] | 135 | nfiles = i = 0;
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[1770] | 136 | G.status = EXIT_SUCCESS;
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| 137 | if (argc == 0) {
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[821] | 138 | struct stat statbuf;
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| 139 |
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| 140 | if (!fstat(STDIN_FILENO, &statbuf) && S_ISFIFO(statbuf.st_mode)) {
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[1770] | 141 | opt &= ~1; /* clear FOLLOW */
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[821] | 142 | }
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| 143 | *argv = (char *) bb_msg_standard_input;
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| 144 | }
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| 145 | do {
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[1770] | 146 | FILE* fil = fopen_or_warn_stdin(argv[i]);
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| 147 | if (!fil) {
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| 148 | G.status = EXIT_FAILURE;
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[821] | 149 | continue;
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| 150 | }
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[1770] | 151 | fds[nfiles] = fileno(fil);
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| 152 | argv[nfiles++] = argv[i];
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[821] | 153 | } while (++i < argc);
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| 154 |
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[1770] | 155 | if (!nfiles)
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[821] | 156 | bb_error_msg_and_die("no files");
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| 157 |
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| 158 | tailbufsize = BUFSIZ;
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| 159 |
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| 160 | /* tail the files */
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[1770] | 161 | if (!from_top && COUNT_BYTES) {
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[821] | 162 | if (tailbufsize < count) {
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| 163 | tailbufsize = count + BUFSIZ;
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| 164 | }
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| 165 | }
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| 166 |
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| 167 | buf = tailbuf = xmalloc(tailbufsize);
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| 168 |
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| 169 | fmt = header_fmt + 1; /* Skip header leading newline on first output. */
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| 170 | i = 0;
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| 171 | do {
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| 172 | /* Be careful. It would be possible to optimize the count-bytes
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| 173 | * case if the file is seekable. If you do though, remember that
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| 174 | * starting file position may not be the beginning of the file.
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| 175 | * Beware of backing up too far. See example in wc.c.
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| 176 | */
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[1770] | 177 | if (!(count | from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
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[821] | 178 | continue;
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| 179 | }
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| 180 |
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| 181 | if (nfiles > header_threshhold) {
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| 182 | tail_xprint_header(fmt, argv[i]);
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| 183 | fmt = header_fmt;
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| 184 | }
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| 185 |
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| 186 | buf = tailbuf;
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| 187 | taillen = 0;
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| 188 | seen = 1;
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| 189 | newline = 0;
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| 190 |
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| 191 | while ((nread = tail_read(fds[i], buf, tailbufsize-taillen)) > 0) {
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| 192 | if (from_top) {
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| 193 | nwrite = nread;
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| 194 | if (seen < count) {
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[1770] | 195 | if (COUNT_BYTES) {
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[821] | 196 | nwrite -= (count - seen);
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| 197 | seen = count;
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| 198 | } else {
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| 199 | s = buf;
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| 200 | do {
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| 201 | --nwrite;
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[1770] | 202 | if (*s++ == '\n' && ++seen == count) {
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[821] | 203 | break;
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| 204 | }
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| 205 | } while (nwrite);
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| 206 | }
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| 207 | }
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[1770] | 208 | xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
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[821] | 209 | } else if (count) {
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[1770] | 210 | if (COUNT_BYTES) {
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[821] | 211 | taillen += nread;
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| 212 | if (taillen > count) {
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| 213 | memmove(tailbuf, tailbuf + taillen - count, count);
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| 214 | taillen = count;
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| 215 | }
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| 216 | } else {
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| 217 | int k = nread;
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| 218 | int nbuf = 0;
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| 219 |
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| 220 | while (k) {
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| 221 | --k;
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| 222 | if (buf[k] == '\n') {
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| 223 | ++nbuf;
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| 224 | }
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| 225 | }
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| 226 |
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| 227 | if (newline + nbuf < count) {
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| 228 | newline += nbuf;
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| 229 | taillen += nread;
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| 230 | } else {
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| 231 | int extra = 0;
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[1770] | 232 |
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| 233 | if (buf[nread-1] != '\n')
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[821] | 234 | extra = 1;
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| 235 | k = newline + nbuf + extra - count;
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| 236 | s = tailbuf;
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| 237 | while (k) {
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| 238 | if (*s == '\n') {
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| 239 | --k;
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| 240 | }
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| 241 | ++s;
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| 242 | }
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| 243 | taillen += nread - (s - tailbuf);
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| 244 | memmove(tailbuf, s, taillen);
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| 245 | newline = count - extra;
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| 246 | }
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| 247 | if (tailbufsize < taillen + BUFSIZ) {
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| 248 | tailbufsize = taillen + BUFSIZ;
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| 249 | tailbuf = xrealloc(tailbuf, tailbufsize);
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| 250 | }
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| 251 | }
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| 252 | buf = tailbuf + taillen;
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| 253 | }
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| 254 | }
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| 255 |
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| 256 | if (!from_top) {
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[1770] | 257 | xwrite(STDOUT_FILENO, tailbuf, taillen);
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[821] | 258 | }
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| 259 |
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| 260 | taillen = 0;
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| 261 | } while (++i < nfiles);
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| 262 |
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| 263 | buf = xrealloc(tailbuf, BUFSIZ);
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| 264 |
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| 265 | fmt = NULL;
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| 266 |
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[1770] | 267 | if (FOLLOW) while (1) {
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[821] | 268 | sleep(sleep_period);
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| 269 | i = 0;
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| 270 | do {
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| 271 | if (nfiles > header_threshhold) {
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| 272 | fmt = header_fmt;
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| 273 | }
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| 274 | while ((nread = tail_read(fds[i], buf, sizeof(buf))) > 0) {
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| 275 | if (fmt) {
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| 276 | tail_xprint_header(fmt, argv[i]);
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| 277 | fmt = NULL;
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| 278 | }
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[1770] | 279 | xwrite(STDOUT_FILENO, buf, nread);
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[821] | 280 | }
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| 281 | } while (++i < nfiles);
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| 282 | }
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[1770] | 283 | if (ENABLE_FEATURE_CLEAN_UP) {
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| 284 | free(fds);
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| 285 | }
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| 286 | return G.status;
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[821] | 287 | }
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