1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * head implementation for busybox
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4 | *
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5 | * Copyright (C) 2003 Manuel Novoa III <mjn3@codepoet.org>
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6 | *
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7 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
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8 | */
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9 |
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10 | /* BB_AUDIT SUSv3 compliant */
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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/head.html */
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13 |
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14 | //kbuild:lib-$(CONFIG_HEAD) += head.o
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15 |
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16 | //usage:#define head_trivial_usage
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17 | //usage: "[OPTIONS] [FILE]..."
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18 | //usage:#define head_full_usage "\n\n"
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19 | //usage: "Print first 10 lines of each FILE (or stdin) to stdout.\n"
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20 | //usage: "With more than one FILE, precede each with a filename header.\n"
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21 | //usage: "\n -n N[kbm] Print first N lines"
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22 | //usage: IF_FEATURE_FANCY_HEAD(
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23 | //usage: "\n -n -N[kbm] Print all except N last lines"
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24 | //usage: "\n -c [-]N[kbm] Print first N bytes"
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25 | //usage: "\n -q Never print headers"
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26 | //usage: "\n -v Always print headers"
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27 | //usage: )
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28 | //usage: "\n"
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29 | //usage: "\nN may be suffixed by k (x1024), b (x512), or m (x1024^2)."
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30 | //usage:
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31 | //usage:#define head_example_usage
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32 | //usage: "$ head -n 2 /etc/passwd\n"
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33 | //usage: "root:x:0:0:root:/root:/bin/bash\n"
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34 | //usage: "daemon:x:1:1:daemon:/usr/sbin:/bin/sh\n"
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35 |
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36 | #include "libbb.h"
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37 |
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38 | /* This is a NOEXEC applet. Be very careful! */
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39 |
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40 | #if !ENABLE_FEATURE_FANCY_HEAD
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41 | # define print_first_N(fp,count,bytes) print_first_N(fp,count)
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42 | #endif
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43 | static void
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44 | print_first_N(FILE *fp, unsigned long count, bool count_bytes)
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45 | {
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46 | #if !ENABLE_FEATURE_FANCY_HEAD
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47 | const int count_bytes = 0;
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48 | #endif
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49 | while (count) {
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50 | int c = getc(fp);
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51 | if (c == EOF)
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52 | break;
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53 | if (count_bytes || (c == '\n'))
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54 | --count;
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55 | putchar(c);
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56 | }
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57 | }
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58 |
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59 | #if ENABLE_FEATURE_FANCY_HEAD
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60 | static void
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61 | print_except_N_last_bytes(FILE *fp, unsigned count)
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62 | {
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63 | unsigned char *circle = xmalloc(++count);
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64 | unsigned head = 0;
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65 | for(;;) {
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66 | int c;
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67 | c = getc(fp);
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68 | if (c == EOF)
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69 | goto ret;
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70 | circle[head++] = c;
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71 | if (head == count)
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72 | break;
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73 | }
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74 | for (;;) {
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75 | int c;
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76 | if (head == count)
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77 | head = 0;
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78 | putchar(circle[head]);
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79 | c = getc(fp);
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80 | if (c == EOF)
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81 | goto ret;
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82 | circle[head] = c;
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83 | head++;
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84 | }
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85 | ret:
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86 | free(circle);
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87 | }
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88 |
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89 | static void
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90 | print_except_N_last_lines(FILE *fp, unsigned count)
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91 | {
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92 | char **circle = xzalloc((++count) * sizeof(circle[0]));
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93 | unsigned head = 0;
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94 | for(;;) {
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95 | char *c;
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96 | c = xmalloc_fgets(fp);
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97 | if (!c)
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98 | goto ret;
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99 | circle[head++] = c;
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100 | if (head == count)
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101 | break;
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102 | }
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103 | for (;;) {
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104 | char *c;
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105 | if (head == count)
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106 | head = 0;
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107 | fputs(circle[head], stdout);
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108 | c = xmalloc_fgets(fp);
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109 | if (!c)
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110 | goto ret;
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111 | free(circle[head]);
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112 | circle[head++] = c;
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113 | }
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114 | ret:
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115 | head = 0;
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116 | for(;;) {
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117 | free(circle[head++]);
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118 | if (head == count)
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119 | break;
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120 | }
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121 | free(circle);
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122 | }
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123 | #else
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124 | /* Must never be called */
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125 | void print_except_N_last_bytes(FILE *fp, unsigned count);
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126 | void print_except_N_last_lines(FILE *fp, unsigned count);
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127 | #endif
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128 |
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129 | #if !ENABLE_FEATURE_FANCY_HEAD
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130 | # define eat_num(negative_N,p) eat_num(p)
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131 | #endif
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132 | static unsigned long
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133 | eat_num(bool *negative_N, const char *p)
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134 | {
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135 | #if ENABLE_FEATURE_FANCY_HEAD
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136 | if (*p == '-') {
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137 | *negative_N = 1;
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138 | p++;
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139 | }
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140 | #endif
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141 | return xatoul_sfx(p, bkm_suffixes);
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142 | }
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143 |
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144 | static const char head_opts[] ALIGN1 =
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145 | "n:"
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146 | #if ENABLE_FEATURE_FANCY_HEAD
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147 | "c:qv"
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148 | #endif
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149 | ;
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150 |
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151 | #define header_fmt_str "\n==> %s <==\n"
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152 |
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153 | int head_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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154 | int head_main(int argc, char **argv)
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155 | {
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156 | unsigned long count = 10;
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157 | #if ENABLE_FEATURE_FANCY_HEAD
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158 | int header_threshhold = 1;
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159 | bool count_bytes = 0;
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160 | bool negative_N = 0;
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161 | #else
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162 | # define header_threshhold 1
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163 | # define count_bytes 0
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164 | # define negative_N 0
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165 | #endif
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166 | FILE *fp;
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167 | const char *fmt;
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168 | char *p;
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169 | int opt;
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170 | int retval = EXIT_SUCCESS;
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171 |
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172 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
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173 | /* Allow legacy syntax of an initial numeric option without -n. */
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174 | if (argv[1] && argv[1][0] == '-'
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175 | && isdigit(argv[1][1])
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176 | ) {
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177 | --argc;
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178 | ++argv;
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179 | p = argv[0] + 1;
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180 | goto GET_COUNT;
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181 | }
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182 | #endif
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183 |
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184 | /* No size benefit in converting this to getopt32 */
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185 | while ((opt = getopt(argc, argv, head_opts)) > 0) {
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186 | switch (opt) {
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187 | #if ENABLE_FEATURE_FANCY_HEAD
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188 | case 'q':
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189 | header_threshhold = INT_MAX;
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190 | break;
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191 | case 'v':
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192 | header_threshhold = -1;
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193 | break;
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194 | case 'c':
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195 | count_bytes = 1;
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196 | /* fall through */
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197 | #endif
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198 | case 'n':
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199 | p = optarg;
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200 | #if ENABLE_INCLUDE_SUSv2 || ENABLE_FEATURE_FANCY_HEAD
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201 | GET_COUNT:
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202 | #endif
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203 | count = eat_num(&negative_N, p);
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204 | break;
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205 | default:
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206 | bb_show_usage();
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207 | }
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208 | }
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209 |
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210 | argc -= optind;
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211 | argv += optind;
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212 | if (!*argv)
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213 | *--argv = (char*)"-";
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214 |
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215 | fmt = header_fmt_str + 1;
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216 | if (argc <= header_threshhold) {
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217 | #if ENABLE_FEATURE_FANCY_HEAD
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218 | header_threshhold = 0;
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219 | #else
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220 | fmt += 11; /* "" */
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221 | #endif
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222 | }
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223 | if (negative_N) {
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224 | if (count >= INT_MAX / sizeof(char*))
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225 | bb_error_msg("count is too big: %lu", count);
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226 | }
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227 |
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228 | do {
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229 | fp = fopen_or_warn_stdin(*argv);
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230 | if (fp) {
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231 | if (fp == stdin) {
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232 | *argv = (char *) bb_msg_standard_input;
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233 | }
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234 | if (header_threshhold) {
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235 | printf(fmt, *argv);
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236 | }
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237 | if (negative_N) {
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238 | if (count_bytes) {
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239 | print_except_N_last_bytes(fp, count);
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240 | } else {
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241 | print_except_N_last_lines(fp, count);
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242 | }
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243 | } else {
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244 | print_first_N(fp, count, count_bytes);
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245 | }
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246 | die_if_ferror_stdout();
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247 | if (fclose_if_not_stdin(fp)) {
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248 | bb_simple_perror_msg(*argv);
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249 | retval = EXIT_FAILURE;
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250 | }
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251 | } else {
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252 | retval = EXIT_FAILURE;
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253 | }
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254 | fmt = header_fmt_str;
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255 | } while (*++argv);
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256 |
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257 | fflush_stdout_and_exit(retval);
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258 | }
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