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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