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 "libbb.h"
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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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32 | { "m", 1024*1024 },
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33 | { }
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34 | };
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35 |
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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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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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43 | if (fdprintf(STDOUT_FILENO, fmt, filename) < 0)
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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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50 | off_t current;
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51 | struct stat sbuf;
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52 |
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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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60 | r = safe_read(fd, buf, count);
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61 | if (r < 0) {
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62 | bb_perror_msg(bb_msg_read_error);
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63 | G.status = EXIT_FAILURE;
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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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69 | static const char header_fmt[] ALIGN1 = "\n==> %s <==\n";
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70 |
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71 | static unsigned eat_num(const char *p)
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72 | {
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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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79 | return xatou_sfx(p, tail_suffixes);
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80 | }
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81 |
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82 | int tail_main(int argc, char **argv);
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83 | int tail_main(int argc, char **argv)
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84 | {
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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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88 | int header_threshhold = 1;
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89 | const char *str_c, *str_n;
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90 | USE_FEATURE_FANCY_TAIL(const char *str_s;)
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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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96 | int nfiles, nread, nwrite, seen, i, opt;
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97 |
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98 | int *fds;
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99 | char *s, *buf;
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100 | const char *fmt;
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101 |
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102 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_TAIL
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103 | /* Allow legacy syntax of an initial numeric option without -n. */
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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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114 | }
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115 | #endif
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116 |
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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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124 | #if ENABLE_FEATURE_FANCY_TAIL
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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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128 | #endif
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129 | argc -= optind;
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130 | argv += optind;
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131 | from_top = G.status;
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132 |
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133 | /* open all the files */
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134 | fds = xmalloc(sizeof(int) * (argc + 1));
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135 | nfiles = i = 0;
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136 | G.status = EXIT_SUCCESS;
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137 | if (argc == 0) {
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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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141 | opt &= ~1; /* clear FOLLOW */
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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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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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149 | continue;
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150 | }
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151 | fds[nfiles] = fileno(fil);
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152 | argv[nfiles++] = argv[i];
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153 | } while (++i < argc);
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154 |
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155 | if (!nfiles)
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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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161 | if (!from_top && COUNT_BYTES) {
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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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177 | if (!(count | from_top) && lseek(fds[i], 0, SEEK_END) >= 0) {
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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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195 | if (COUNT_BYTES) {
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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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202 | if (*s++ == '\n' && ++seen == count) {
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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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208 | xwrite(STDOUT_FILENO, buf + nread - nwrite, nwrite);
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209 | } else if (count) {
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210 | if (COUNT_BYTES) {
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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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232 |
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233 | if (buf[nread-1] != '\n')
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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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257 | xwrite(STDOUT_FILENO, tailbuf, taillen);
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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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267 | if (FOLLOW) while (1) {
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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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279 | xwrite(STDOUT_FILENO, buf, nread);
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280 | }
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281 | } while (++i < nfiles);
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282 | }
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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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287 | }
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